Glass Circle News_No.135, Jul 2014

iciS1S

Geometry on the table

The Higgins
Stained glass

Reports
Reviews and news

Diary

Glass Circle News
ISSN 2043-6572

Vol. 37 No. 2 Issue 135 July 2014

published by The Glass Circle

) ince last writing I have

been to Detroit to choose a

suitable hotel for our visit to
America next year, and just

as well that I did so as the first one I found,

on the internet, was dreadful. This will
be our base to visit first the Henry Ford
Greenfield Village, with its American

glass and a truly all-American museum.
Next we will visit nearby Toledo, with

probably the second or third best glass
museum in the US. Then we will fly to
Corning, difficult to get to usually, and

absolutely amazing; by then their new
extension should be finished. After that,

by coach to Brooklyn, which will be our

base for the Brooklyn museum and the
museums on Manhattan Island. The trip

will be in the middle of May next year,

so if you have other places or people you
wish to visit in American you can either
do this before we arrive in Detroit, or

after we finish in New York.
I have also been to Malta, the birthplace

of Mdina Glass in 1968, opened by

Michael Harris and Eric Dobson. By

1973 Dom Mintoff had made Harris’s

position impossible and he moved to
the Isle of Wight. The Mdina company
continued to be run by Harris’s first

apprentice, Joseph Siad. Harris had been
very influenced by Sam Herman while

at the Royal College of Art. There are

now three glass houses on the Maltese

islands, all producing rather similar

glass, apparently quite successfully, and

not much changed in style in 48 years.

The philosophy seems to be, `if it still

sells, why change it?’
This brings me to the problem of

dating old glass. We tend to forget that

good glass designs have a very long life.

Baccarat designed the Harcourt goblet in
the 182os and it is still production today.

I have a plain Prussian three-ringed

decanter, apparently caoo, bearing the
cipher of Queen Victoria. I have recently

been helping a Japanese Museum update

the identification of some of their

glass. After dating some of their glass,
I discovered that their records showed

that they had bought much of it new,

often
20 to
4o years after my estimation

of the original date of production.
In my last letter I quoted an article

by Peter Korf de Gidts concerning the
development of lead glass, which has

lead to an open discussion on page 4.
John P. Smith

A pair of very fine cut blue glass vases with their original ormolu mounts. English c.1770. Both the British Museum

and
the Corning Museum
of Glass bays relatsd blue glass circr

EDITORIAL

CONTENTS

Chairman’s letter

Letters

My favourite glass

On knopping

Editor

Jane Dorner
[email protected]

9 Collingwood Avenue, N10 3EH

Design and layout
Athelny Townshend

[email protected]

Neither the Class Circle nor Any of h
.

officers
Or
antmitxte

members beer any responsibility tor the views expressed in this

publication, which are chose of the contributor in each case. Every

effort has been made to trace and acknowledge copyright in the

photographs illustrating articles. the Editor asks contributors to
clear permissions and neither the Editor nor the Glass Circle is

responsible for inadvertent infringements. All photographs are

Printed by
IVEcropress Printers Ltd
www.micropress.co.uk

Next copy date:

15 September for the November edition

COVER ILLUSTRATION:
A
panel of the Great
East
Window of York Minster

Glass Circle News Issue 135 Vol. 37 No. 2

ked

LETTERS

Letters to the Editor

Editor’s note

All letters

about a
previous

edition of

the magazine
refer to

Vol. 37 no.

2, Issue No.

133 unless
otherwise

stated.

What is this

ship?

The letter about the engraved ship in

Issue no. 131 page
29
was incorrectly

attributed to David C. Watts and

was in fact written by Stephen

Pollock-Hill. An apology to both
writers.

Editor

Breaking mirrors brings seven

years of bad luck

D
eaders may be interested in

an item I found in the
Daily

Express,
28 March 2014. It reads:

This superstition has its origin

in ancient Greece before mirrors

were invented. In a form of
divination called catoptromancy,

shallow bowls filled with water
were used to tell a person’s future

and any distortion meant bad
news. The first mirrors fashioned

from precious metals were
unbreakable but in 15th-century

Venice — where glass mirrors

backed by silver coating were first

produced — they were so expensive
that any servant who broke one

would have to offer seven years of

labour to pay back the debt.
Michael Vaughan
Lanarkshire

Books acquired
n the letter section of your last

I issue Stephen Pohlmann kindly
offered a reader, for free, a couple

of books published by Mallet &

Son on historic glass. I responded

and have just received these
beautifully illustrated catalogues

published nearly 25 years ago and
co-written by our chairman, John

P Smith. I also received a copy of

Harold Newman’s
Dictionary of

Glass
which, as a beginner, I find

most useful. I am very grateful

to Stephen for his generosity in

sending these books – especially
as he lives in Tel Aviv. He did ask

me, in return, if I could find him a

Verzelini in a flea market for £10 –

well, you never know what may be
round the corner!

Chris Smith

West Sussex
Erratum

I
n my piece on density measure-

ment in glass (page 4) I find that

the 4th paragraph states that ‘a

density of 2.75 notionally repre-

sents about 5% lead’ . It should say
‘15% lead’. My apologies for not
noticing earlier.

David Watts

Website reinstated
Dr Watts tells us that his website

www.glassmaking-in-London.

co.uk is now back running after
having been down for several
months as the result of vandalism.

Editor

Night, night

I
is

hard for us to imagine how

dark large houses were at night
in the 18th century. This hand-

held lantern from Duff House,

Aberdeenshire would light you to

bed (continental 18th century). As

seen in situ.

Jam P. Smith

Lead
glass: Point

I
guess that John Smith knew that

his report on Peter Korf de
,
Gidts’

article on the invention of lead

glass would be bound to attract

my response. Peter is not the

first to centre Dutch involvement

on Johann Glauber, a German

alchemist who died in Amsterdam

in 1668. Glauber was not the only

alchemist of his time whose main
interest was the transmutation of

a base metal, notably lead, into

gold. Ruby glass and lead glass

were hopeful steps along the way.
Unlike Johann Kunckel, who was

briefly thought to have made the

magic discovery, Glauber was not

a glassmaker.

Lead used in glass-making goes

back to antiquity and traditional

continental lead glass was well-
established by the 14th century. It

is a form of lead silicate made by

melting together silica (sand or

crushed quartz) with lead oxide.
It contains no alkaline flux or any

other ingredient. Its particular use

was in making certain coloured

glasses. It was never used for
making colourless Cristal’ as it is

deep amber in colour. Cristal was

made from a mixture of purified

soda containing some lime, mostly
from littoral or shore-loving

plants, and crushed quartz or

flints.

Johanne Baptiste da Costa,

an Altarist working in Holland,

certainly knew all this when he

came to England. He was possibly

working at the Bear Garden

glasshouse when commissioned

by George Ravenscroft to make

calcedonio at a small furnace he

organised in the Savoy Palace.

Calcedonio is an expensive glass
used for making small ornaments.

It is made by stirring a colouring

Glass Circle News Issue 135 Vol. 37 No. 2

LETTERS

Ravenscroft jug

1676-78 from the
Higgins (see page

12)

powder containing silver into best

cristal containing added lead glass

to produce the swirling coloured

effect of agate. Because of English

coal fired furnaces dating back
to the days of Mansell saltpetre

was added to the cristal batch to
protect against coal discolouration.

The remarkable discovery was
made that saltpetre discharged the

amber colour caused by lead. And
no less important, it stopped the

lead from attacking and destroying
the glass pots — another reason it

was not used on the continent.

This melt was the first English lead
crystal patented by Ravenscroft.

Saltpetre seems never to have
been used in glass batches outside

England — Venetian cristal was

better than anything produced in
England up to that time. But it

took another hundred years before

this `secret’ of English lead crystal

leaked out.
I agree with Peter Korf de Gidts

that it was da Costa’s expertise

that resulted in the discovery

of English lead crystal. But it is
unarguable that it could only have

happened in England at that time
as a result of the ban on wood

firing introduced by King James I

and VI back in 1615 and Mansell’s

adoption of saltpetre. As always,

it is the boss who took out and

exploited the patent that got the

credit!
A detailed and fully referenced
account will appear in the shortly

to be published and edn. of my

book,
A History of Glassmaking in

London from the earliest times to the

present day.
David
C.

Watts

London

Lead glass: Counterpoint

J ohann Rudolf Glauber (1604-
1670) was not a glass-maker.

He was a chemist, a pharmacist

and a technologist and it was his
own curiosity that lead him to
new forms of scientific research.
He certainly was not an old

school alchemist, who was only

interested in making gold out of
lead; he knew a lot about glass.
He took advantage of its multi-

purpose character and its known

properties in his experiments.
He was a freelance entrepeneur,

highly esteemed, with his own
laboratory where he worked at his

own research and as a commercial
producer for others.

In the middle of the 17th

century Glauber occasionally
hired room and furnace time in
the Glasshouse ‘De Twee Rozen’

(The Two Roses) which existed

in cosmopolitan Amsterdam from

1657-1679. Here he experimented

with the colouring of glass.

Like many others, he was of the
opinion that glass could take

on any colour according the
chemicals and processes used.

His experiments in making

coloured glass — as well as his
results — did not go unnoticed. As

in most glasshouses in northern

continental countries, the most
important jobs were executed by

highly qualified workers from

Venice and Altare. Apart from

experience
where production was
concerned they had an enormous

knowledge of raw materials and

chemicals, furnace temperatures,
and so on. Cross fertilisation
between chemists and glass

workers was a logical consequence.
Between both professional groups
there was exchange of the latest

developments in glass-making

which were strictly kept secret
and never put into writing. The
economy prospered and the

cristallo glass became extremely

popular with the wealthy. New

glasshouses were established

by adventurous and greedy
entrepreneurs who had no idea
how to make cristallo. They badly

needed the professionals who were

snatched from their employers

by the lure of high salaries. This
explains the itinerant life of the

glass-makers. And every time they
took their secrets and experience

with them. Italian glass-workers
like the Venetian glass master

Nicolao Stua, Giacomo Scapitta

and Bastiaen Maistre worked in
the glasshouse The Two Roses’

at the time that Johann Glauber
did his experiments with lead and

glass colouring. Bastiaen Maistre
worked later in the glasshouse of
the Altarist glass-makers Baptista

da Costa and Jor Odacio in the
chapel of the Jacobspital in the
Hezelstraat in Nijmegen (1658-

1674). Doubtless all of them

were totally aware of the latest
developments in their field and

shared their knowledge with their
confreres in Europe. And so also

did Baptista da Costa, Seigneur

de Baramont. It was a pleasant

surprise that David Watts wanted
to react to the resume of my

lecture and that he agrees with me
that Da Costa’s expertise resulted

in the discovery of lead glass in
England, facilitated by George

Ravenscroft. It is only obvious and

logical that Ravenscroft registered
his patent since Da Costa was not
equipped to apply.
Peter Korf de Gidts

The Netherlands

C
ass
Circle News Issue 135 Vol. 37 No. 2

Glass Circle News Issue 135 Vol. 37 No. 2
FAVOURITE

My favourite glass

eg
—

agonised over

which glass was my
favourite; in the

end the decision

came down to why I have a
wide interest in almost

every variant of glass from

the 16th to 21st centuries.

It is the nature of glass

itself as well as the wonder

of who may have owned,
enjoyed and used an item.
At first sight my choice could

appear plain, uninteresting and

easily passed over. To me, it says as
much through understatement as

a piece of cut, engraved or coloured

glass. It is a simple lead glass beer
or water beaker, possibly from the
first decade of the 18th century and

similar to those glasses illustrated

in John Greene’s letters to his
Venetian glass maker about 1670.

The height almost matches its
diameter and it is squarer in profile
than the tumbler of tapering form
that became popular later. The

colour, nature and qualities of the
metal are very similar to the bowls

of heavy balusters.
In plan, it is not quite round,
neither at the base nor at

the rim. It stands 4
3
4″ (11.8

cm) high and is 4″

cm) wide at the lip and

3
1
/s” (7.8 cm) at the base

and holds an imperial pint

(568 ml).
As a piece of historic glass it is

perfect in its imperfection and tells

us exactly how it was crafted by its

creator. Each action of the maker
is permanently recorded in the
fabric of the glass. The tool marks

and striae in the glass make an
otherwise plain glass come alive.
It is a ‘fossil’ in glass preserving a

moment of human endeavour, like

the footsteps of prehistoric man

forever preserved in rock.
In the hands of the gaffer in the

chair, the jacks danced all over
the surface of the bowl as it was

formed. This has left the material

permanently frozen in diagonal

swirls around the body of the glass,

giving a cross-over
effect
where

they rise on one side and fall on

the other. A pair of vertical striae

show us where the same tool slid
out of the bowl against the wall

of the glass. Another single mark

indicates were he hesitated just
momentarily when opening out

the bowl. On the rim, a finger can

just determine the very slightest

bump and below it, a distortion
in the glass tells us where the

smoothing tool used to finish the

lip came off the glass.
It is peppered with bubbles and

impurities and has a particularly

prominent cluster of seeds about
two-thirds of the way up the bowl,

distorting the surrounding glass,

as if they had been dropped onto

the surface when it was a semi

solid state. The rough pontil is

pushed up just enough to raise it

off the table and is haloed by wear
marks equivalent to many hours of

use and gallons imbibed.

It probably took an experienced

workman not more than three

minutes to make this glass as

he deftly and without conscious

thought picked up each tool in

turn. In a single glass, those three

minutes of a distant life still echo

30o years later, if you pause to look
hard enough.

RIGHT:

natural daylight
reveals tooling

marks

Paul

Weddell

KNOPS

On knopping:

Open letters between Patrick Hagglund, Simon Wain-Hobson

and Mark Taylor

0e
ar Simon,

I wish to record

appreciation,

gratitude

and

delight to yourself and Athelny
Townshend for the ground-

breaking articles in Issues 13z and

133. Something that had troubled
me for so long now seems to be

solved to my personal satisfaction,
namely, how 18th-century opaque

twist stems were created by the

gaffers of that period. The papers
are surely important advances
in the documenting of the

processes most likely used by the

glassmakers of 18th century in
creating the opaque twist stems

we all admire.

I recall, when we spoke in

London, that you raised the

further issue of stem knops and
how they may have been made. I

wish to offer a tentative opening
to the discussion of this topic.

I fully realise this is most likely

only the tip of the proverbial

iceberg in our understanding of
how these familiar stem knops

were made, but an opening gambit
nevertheless.

I have given much thought to

how these were made, and initially

assumed that the stem was twisted

to completion before the knop was
created by compressing the gather
in some way, thus creating a bulge

we refer to as a knop. It did not take
me long to realise that that just

would not work. Knops in opaque

twists reveal that the twisted canes

in the knop are thicker in the mid-

point (maximum diameter) of
the knop than that at where the
knop gives way to the stem on
each side of the knop. I checked
the illustrations in Bickerton’, and

they mostly appear to show this

characteristic (refer Bickerton figs
697, 698, and 1193). His illustration
fig. 1175 does not show this very

clearly, but a similar stem from my

own collection (see fig. t) certainly

does — what he refers to as a
MSOT

(multi-spiral opaque twists).
This observation persuaded

6
me that the knop must have

been decided upon during the

twisting process. The continuance
of the twist must have been carried

out on each side of the knop,
control being kept by use of two

sets of jacks or other appropriate
tools during the additional

twisting. This suggests that knop

creation may have required more
than just one pair of hands to
achieve the technique successfully.

Another observation is that the
twists either side of the knop are

often not quite the same, possibly

indicating that the twists either

side of the knop were separate
operations. The `single series’

opaque twist in my collection,

as mentioned above, shows this

quite clearly (fig. I).

The examples in Bickerton

of
DSOTS
(double-series opaque

twists) with knops show that

the twists within the knops are

decidedly strange and uneven in
appearance (see Bickerton figs

697 and 698). I do not have one
of these in my collection to be

able to compare at first hand.

This all seems to point to the
knops being created something
like the way I suggest without

going into the mechanics
of changing the pontil
rods at the different

stages of the process.
For similar reasons, I

concentrate on opaque

twists, though the basic

techniques probably apply to air

twists as well.
I notice that I am unable to find

any discussion of this topic in the

standard literature. Hartshorne,
Francis, Thorpe, Bickerton,

Haynes, et al° do not appear to
raise the question of how the

knops were made. In fact, Lanmon

(zoii) in The Golden Age of
English Glass 1650-1775, whilst
briefly discussing the making of

air and opaque (enamel’ in his

terminology) twists (pages 184-

187), avoids mention of knops
altogether. I have not found
any solid knop-making either

in the splendid demonstrations
recorded by William Gudenrath

of the Corning Museum of Glass

in New York on DVD nor online.
The latter does make hollow
knops, but they are a completely

different technique altogether.
I have deliberately kept this

suggested description as simple

as possible to launch the topic for
discussion. Please let me know

your thoughts.
Patrick

ear Patrick,
I agree with

you, the art of

knopping has

been given even shorter shrift

than the making of opaque

twists, which was slim in itself.
Your point about the canes

in the knop being thicker than

in the stem is well made and
proves that stems were drawn

away from the knop. Playing the
poorly-paid devil’s advocate –
even he is hard up these days — I

can see two possibilities. First,
a preformed carrot of parallel
opaque canes is heated up and
simultaneously drawn and
twisted at one end away

from the middle. When
the other end is so

treated this would

leave the delightful

MSOT
with centre knop

in your collection (fig. 1).

This is your scenario. The

alternative is to work from a

preformed carrot of already

twisted glass and simply draw

on one end followed by the

latter. So which is it
If a preformed twist was used

and drawn, the angles (alpha

glyph, gamma glyph) subtended
by the twist in the stem would

have to be greater than that
in the knop (13) because the

diameter of the stem is reduced

as a result of drawing; in short

y,
(fig. za). If twisting and

4- drawing were simultaneous,

Glass Circle News Issue 135 Vol. 37 No. 2

BELow:fig. 1

Patrick Hagglund’s

knopped multiple

spiral opaque twist

stem

4ar

oitatiW

lae

RIGHT & OVERLEAF:

fig. 3 A set of photos

showing the
making

of a plain knopped

stem as
found in

balustroid glasses
(See next page)

BELOW:
Figure 2

A
KNOPS

everything depends on the ratio

of twisting to drawing — twisting

tends to diminish the angle of

the opaque white threads while
drawing tends to increase it. For

your
MSOT
stem the angles above

and below the knop are less than
that within the knop (fig. 2b). As

the diameters of the stems on

either side of the knop are the

same, this rules out the hypothesis
that there was a preformed twist

that was merely drawn on either

side of the knop. Inspection of an

ale glass of my own with a similar

stem, as well as Bickerton figs 61′-
616, all show that the angles above

and below the knop are smaller

than that of the canes in the knop.
From this we can conclude

that
OT
knops of this form were

made from a carrot of parallel

opaque canes, the knop proper

arising from what is left following

simultaneous drawing and
twisting of the stem either side.

Once drawn to a diameter of

approximately ‘ cm, bowl and feet
could be added.
There is a category of
OT

wine glass where it seems likely
that the preformed carrot was

added directly to the bowl and

subsequently drawn, twisted

and knopped (fig.
2C;
Bickerton

figs 608-610). I recently bought

a highly unusual glass belonging

to this family where there was no

twisting at all — the opaque canes
remaining dead straight (fig. ad).

It is less attractive compared to

its sister (fig. 2c) and emphasizes
the harmony just a little twisting

brings to a stem. The key point,

however, is that it has two small

knops proving that they could be

formed during drawing the carrot.
Like you I suspect that air-twist

knops were made in a similar

manner but need to think it

through a little more. These are

some immediate thoughts that come to mind and they square
up with your own. Let us invite

comments from other readers.

Simon

Glass Circle News Issue 135 Vol. 37 No. 2

KNOPS

ear Patrick and

Simon,
The Editor asked

me to add to this

discussion and I hope to elaborate
further in a later edition. To
make a central knop in a stem is
not difficult, and only needs one

glassblower to make it.
The starting point is a short,

plump cylinder of glass, either

attached to the bowl or to a bit
iron. A central knop is produced by

carefully squeezing and stretching
the glass with the jacks alternately

at either side of the knop a little

at a time, occasionally pushing
against the knop to reinforce its

shape and to cool it slightly. A
basal knop and a knop at the top
of the stem can also be produced

at the same time.
The photographs in fig.
3
show

some of the steps needed to make
the simple knopped stem. This

stem took about one minute to
make and required no reheating.
Knopped stems with air,

opaque and colour twists are
more difficult, and may have had a

twist introduced into the original
cylinder, which may be twisted
further during the stem-making,

with the twist at either side of the
knop individually tightened. This

would account for the sometimes

differing tightnesses of the twists

above and below the knop.
Air-twist knopped stems are

the most difficult stems to make

as the air can easily be squeezed to
one area or another of the stem by

overuse of the jacks.

There are one or two early films

which illustrate the knop-making
process, such as this one of a gaffer

at Whitefriars in the 193os:

www.youtube.com/

watch?v=nQGO3wDesLE

Mark Taylor,

Georgian Glassmakers

Notes

1.
Bickerton, L.M. (1986) Eighteenth

century English drinking glasses, an
illustrated guide. Woodbridge: Antique

Collector’s Club, znd revised edition.

2.
References given in Issues nos. 132

and 133.

Glass Circle News Issue 135 Vol. 37 No. 2

TABLEWARE

Geometry on the dining table
°Davenp
or
t
g
lass

BELOW RIGHT:

fig. 3a
Cut desert

plate (see detail
overleaf)
V

ery few of our

members collect

tableware, which

is a pity because

although drinking glasses are

attractive and interesting, the best,

and most expensive, items made
by glass manufacturers in

the early 19th century, are

larger items for the table.
Very few people were,

or are, as extravagant as
the Prince Regent, who,

after being entertained by the
Liverpool Corporation in i8o6 to a

lavish banquet including specially

commissioned glass from the local

glass-house of Perrin Geddes,
declared ‘I want the same (fig. t).

Four years later the service was

delivered, the most extravagant

ordered either before or since.
Most of the service is still in
Windsor Castle, but some

escaped and may be seen in the

best museums and collections
of the world. The story of their
escape is intriguing. Soon after her

coronation in 1837 Queen Victoria

gave a banquet for her relatives

and other senior nobility. This

service was used at dinner, and

after dinner the Queen, probably

not a fan of George IV or his
lifestyle, invited her guests
to take home items from

the table. Some did.
The Prince Regent also

bought a larger, and less

extravagant, service from

John Davenport, decorated using
his recently patented method of

stencilling a pattern of low melting

point ground glass to the glass,

and then firing it.

The Corning Museum of Glass

has a pineapple stand, accession

no. 2005.2.4, which is made in two

pieces and a tour
de force
of cutting

(fig. 2). The museum attributes

this stand to the London maker

Apsley Pellatt. This stand is 45.5

cm high.

The Regency cutters became

LEFT: fig.

Perrin Gedes

‘Prince of Wales’
decanter

BELOW:
fig.
2

Pineapple stand,

attributed to Apsley
Pellatt
by

John P

Smith

Glass Circle News Issue 135 Vol. 37 No. 2
9

TABLEWARE

extraordinarily proficient at

complex cutting. The plate
illustrated (fig. 3 a & b) is one of

a set of io dessert plates, which

at the time of manufacture,
would have been as expensive,
or probably more, than the most
highly decorated porcelain. When

decorating ceramics, if the brush

slips, the enamel can be removed
and reapplied, but there is no such

second chance when cutting glass;
once glass has been ground, that
is it. The plates were first marked

out by specialist markers, using

a special turntable with pegs,

and then the cutters, in England
working overhand (that is on the
top of the wheel) and looking

through the glass to see the depth
BELOW

LEFT: fig.
3b

Cut desert plate

detail (see fig. 3a

previous page)

ABOVE LEFT:

fig. 4 Butter dishes

with
‘Van
Dyke’

border

AeovE:fig.
5

Claret jugs, probably

of Irish manufacture
of the cut, would cut the glass.

They then brought the plates to

a fine polish using a cork wheel

and a putty-like powder. It was
only much later in the century

that hydrofluoric acid was used to
polish the original matt cutting.

This acid polishing also removed

the sharpness of the cutting. Some

early deep cutting almost feels

dangerous to handle.
Butter dishes would have been

used, butter to go with biscuits,

and the pair here (fig. 4) have

serrated boarders, rather fancifully
called ‘Van Dyke’ borders by
dealers, after the form of a typical

Van Dyke beard, although this
term was not used at the time

when they were made.
There is much dispute

concerning Irish glass, and the

contemporary records are not
very helpful, but it is generally

agreed that certain forms, such

as piggins, and canoe shaped
bowls, are nearly always s of Irish
manufacture. Particularly large

spouts are also thought to be Irish,

such as are on the pair of claret

jugs illustrated here (fig. 5). These
never had stoppers, the claret was

always finished at one sitting;

Glass Circle News Issue 135 Vol. 37 No. 2

1
0

TABLEWARE

RiGHT:fig. 8

Detail of ‘hobnail’
cutting

none was left over at the end of the

meal, particularly not in Ireland.

The jugs are extraordinarily heavy

as they are pillar-cut, so needing
very thick blanks. This form of

cutting was very expensive to do

as it cannot be done on a mitred

wheel; each pillar has to be

smoothed round, which is very
time-consuming.

The trio of coloured vessels

(fig. 6) was first illustrated in

our exhibition at the Wallace

Collection Palace to Parlour’ and

they are very beautiful. They all

date from around 1830. The amber

jug is pillar-cut and the two claret

jugs, red and aquamarine are
panel-cut.

Except for white wine, wine

should never be served in coloured

glass, since you cannot admire the
depth of colour in the wine. Only

spirits such as gin can be served

in coloured glass as no one holds

their gin glass up in the air and

says, ‘Oh! What a lovely colour’.
In many ways the lack of coloured

glass is regrettable. Coloured glass
looks particularly fine on a white

table cloth. The pair of green

decanters (fig. 7) would not have

been used for port, as the trolley

suggests, but for white wine,
almost certainly in the best circles
from Germany, the original home

of our Royal family, and at this
time it was usually -of great age,

at least zo years was considered
preferable.

Finally the last illustration (fig.

8) is a close up of a decanter of

around 1830 showing hob-nail

cutting, the title of this cutting

also being dealer’s invention,
rather than the name used at the

period of manufacture. The ‘hob-
nails’ are astonishingly even in this

example. No modern cut glass

can approach this quality, even if
the craftsmen still exist to do this

work, and they probably do, the

time required to cut and polish to

this quality would put the cost of

such a decanter towards f.i,000.

ABOVE:

fig.
6

Three coloured jugs

all dating to around

1830

ABOVE
FLIGHT:

fig.
7

Pair
of green

decanters, probably

used for white wine

Glass Circle News Issue 135 Vol. 37 No. 2
11

NEW GLASS GALLERIES

The Higgins

6
,
3

n 21 June 2013 The

Higgins

Bedford,

pened with a special

dawn till dusk’ event.

This marked the end of a major

£5.8 million redevelopment
project which united two separate

organisations: the Cecil Higgins
Art Gallery and Bedford Museum.

The transformation has been total,

three historic buildings have been

joined together and redeveloped,
creating new galleries and modern
visitor facilities, and the collections
have been reinterpreted and

redisplayed throughout (fig. 1).

The Redevelopment has been a

long process. The Cecil Higgins
Art Gallery closed in June
2007

to protect the collection from

the first lot of building work,

the redevelopment of Bedford
Gallery. This building had lain
empty for nearly
35

years, but with

funding from the Department
for Communities and Local

Government it was turned into

a new exhibition space with two

large galleries. Fundraising for
the second phase of building

work was affected by
the financial pressures

of the recession, but
work finally began in the

summer of
2011.

When I arrived as Keeper

of Fine and Decorative Arts in

2009
the majority of the objects

had been packed, so for a few

years I was the Keeper of Boxes,

unable to see the marvels that

lay within. The hundreds of

boxes that surrounded
me had been expertly

packed by specialist

art handlers and

staff. Each piece
from the collec-
tion was cleaned,

condition report-
ed, documented

and packed in

acid free tissue.

The boxes were
then moved to a
purpose built off

site store, where

they were to remain
until their cases were
ready and the process of

unpacking could begin.
Even though I only

packed a portion of the

ABOVE:

Fig. 1 Newly

opened Higgins
BELOW:

Fig. 2 Author

moving Sam

Herman
vase

1969
RIGHT:
Fig. 3a

Ravenscroft jug

1676.78

NEW GLASS GALLERIES

collection, I think it is true to say

that unpacking glass and ceramics
is a far more nerve wracking,

lengthy experience than packing

(fig. a). It is testament to our staff

and art handlers that every piece

survived the closure intact.
Some pieces in the collection

were more challenging to move

and store than others. The pieces
that gave us the most sleepless
nights were those by George

Ravenscroft. The Higgins has

three pieces of Ravenscroft, two of

which are marked with the Raven’s

head (fig.
3).
All three come from

Kirkby Mason’s collection of

Old English Glass which was

sold at Soetheby’s in
1929

after

his death. Cecil Higgins bought

several items from the Kirkby
Mason collection but none as rare

or as delicate as the Ravenscroft
pieces. Ravenscroft, an importer

of Venetian glass, had taken out a

patent in
1674
for a ‘particular sort

of Christaline Glasse resembling
Rock Cristalr. His first attempts

were plagued with problems, but

in
1676-77
he appeared to have

perfected his glass and marked it

with a Raven’s head as a mark of

its quality. Ravenscroft, however,
hadn’t quite fixed the problem

with his glass and the few pieces
that still exist marked with the

Raven’s head seal are prone to

crizzling. To stop the Ravenscroft

glass crizzling from developing
any further, the glass has be kept

at low humidity and a stable
temperature.

The redevelopment called for

the glass to be moved from its

humidity-controlled case to an
offsite store two miles away, where

it would stay until we reopened.
We sought advice from both the

Fitzwilliam and British Museum

as well as an independent
conservator as to the best way to

go about this. To minimise any

changes in temperature en route,

a specially-built packing crate

was made, lined with foil. The
temperature of the store that it

was going to had been monitored
for several weeks to make sure
that it remained at a stable level

and when the glasses arrived they

were unpacked, which not only

gave them room to breathe but

also allowed for regular checks
on their condition over the next
two years. Handling the glass was

very different from what I had
expected. After years of being told

how fragile it was, I expected it to

be light and delicate. In fact it was

quite solid and weighty and far
more agreeable to move than its

Venetian counterparts.
When it was time for the

glass to return, the process was
repeated. The glasses were the

last pieces to be installed in the
new Design gallery and have been

given pride of place in their own
specially designed case. The case
may look like all the others, but

hidden within the frame is a de-

humidifier working silently to

keep the glass safe. It is even set

to sound an alarm to tell us of any

problems. I am happy to say that a

year down the line the case is still

working well and the Ravenscroft

glass has come out of its adventure
unharmed.

The returning of the

Victoria

Partridge

BELOW:
Fig. 3b

Ravenscroft bowl

1676-78

n.b A further
Ravenscroft piece

from the Higgins
Collection is

illustrated on

page 4

RIGHT:

Fig. 4 Cecil Higgins

by Glyn Philpot

Ravenscroft glass marked the

end of the redevelopment and the

beginning of a new chapter for the

Cecil Higgins Collection. A letter

in this publication (Issue no.
133)

saying ‘fellow glass collectors will

find a visit worthwhile echoes

one written
64
years ago at the

time of the first opening of the

Cecil Higgins in
1949.

Housed

as its founder had asked ‘in the

unusually friendly setting of the

former Higgins family home, it

was the first public art gallery to

open in Bedford. The collection

that Cecil had amassed during

the last ten years of his life was

described as bearing the ‘stamp

of thoughtfulness’ and the glass
collection was ‘acclaimed as one of

Glass Circle News Issue 135 Vol. 37 No.
2

NEW GLASS GALLERIES

those which glass students must
not fail to visit’.
What makes Cecil’s collection

unique is that, unlike other

benefactors who have endowed

institutions with a lifetime of
collecting, Cecil Higgins (fig.

4)
collected with the specific

intention of opening a museum.

He devoted the last ten years of

his life to this aim.
Cecil’s early life showed no sign

that he was to become a museum
founder. He was the youngest

son of a family of brewers, his

grandfather Charles (1789-1862)
had been a tenant of the Swan
Inn, a large hotel which still stands

today on the banks of the river

Great Ouse. Charles realised that
he would be able to increase his

profits if he brewed the beer that
he sold, so in 1837 he leased the

land known as Castle Close (fig.

5)
(named so because the remains

Bedford Castle are in its grounds)

from the Duke of Bedfordshire,

with the intention of building a
brewery and a family home.

The Higgins & Sons brewery

(fig. 6) became a successful

business, which Charles handed
down to his son George who in

turn left it to his sons Lawrence
(1849-1930) and Cecil (1856-1941).

The family were pillars of their
community serving as Mayors,

Justices of the Peace, Magistrates
and Councillors. Cecil served as

a Bedford Magistrate, but chose
to live away from the family in

London. In the City he played

the part of ‘a rather bored man

about town; being driven in a
custom-made Rolls Royce which
allowed him to keep his top hat

on and taking a box at the opera
(which he attended in full white
tie and in which he once boasted

about falling asleep during a
performance of
The Ring).

He must have kept one eye on

the family business though, as

when it showed signs of struggling
in 1907, he persuaded his brother
Lawrence to retire and started
running the brewery from his

home in London. The family home

was sold in 1910 and Lawrence, the
last Higgins to live there, moved to
Somerset. The business remained

in Cecil’s hands until 1928 when,
as neither he nor his brother had

married or had children to pass it

on to, it was sold. Two years later
Lawrence died and, with the bulk

of his estate going to Cecil as well

as the profits from the sale of the
brewery business, Cecil became a
very wealthy man.
It was at this time that he

decided upon the idea of setting
up a museum. He was

73,

and

thought that he probably had

about ten years left to live (in
fact he had 12) and that he

would devote those years

to a career as a serious

collector. He enlisted the

services of a young glass
and ceramics expert at

Sotheby’s as his advisor
and for the next ten years
collected over 300 pieces of

glass and over moo pieces of
ceramics. We know from the
few receipts that relate to the

glass collection that most of
the glass was bought through

the London dealer Cecil Davis

on Kensington Road, as well

as from private house sales. On
return trips to Bedford he would

also frequent ‘Frederick Jones
Antiques’ on Tavistock Street.

The bulk of Cecil’s collection

is formed of ceramics, especially

early English and Continental

porcelain, and British glass from

around 1675-1810 (like many of
his generation his taste did not
reach the Victorian period). As he

was collecting with the intention
of opening a museum, Cecil also

collected ceramics and glass
that could tell the history
of the inventions and styles
that led to the glass and

ABOVE LEFT:

Fig. 5

Castle Close about

1955

ABOVE:
Fig. 6

Castle Brewery
about 1885

Glass Circle News Issue 135 Vol. 37

Tour to the USA

Spring 2015

The plans for our trip to the USA are advancing well.
We leave for the USA from Heathrow on Tuesday 12th May, and return on Thursday 20th May. There is a

possibility of staying on longer in the USA for those who so wish.

Our Schedule
Arrive Detroit Tuesday 12th May

Stay three nights Courtyard by
Marriott 5200 Mercury Drive,

Dearborn, MI 48126 a very pleas-

ant hotel which I have visited, quiet

and spacious.

Wednesday 13th May: visit Henry
Ford Museum. This museum is near

the hotel and will give us a leisurely

first day. Wonderful museum of the

American way of life, with a display
of American glass.

Thursday 14th: visit Toledo Mu-

seum of Art. 80 minutes away by
coach. Fine museum with a special

new section devoted solely to glass.

We will have lectures, a visit to a
nearby Tiffany windowed church,

and a wine tasting.

Fridayl5th: fly from Detroit to
Corning

Stay three nights Radisson Hotel
Corning 125 Denison Parkway East

Corning NY 14830 The only de-
cent hotel in Corning. The museum,

library and Corning town will keep
us fully occupied for the 2 1/2 days

we are there. The hot glass studio

will be running and an new exten-

sive contemporary glass wing will be

opened just before our arrival.

Saturday 16th & Sunday 17th:

Corning Museum of Glass

Monday 18th: Coach to Brooklyn
About 5 hours, but the only sensible

way to leave Corning.

Stay 3 nights at the Brooklyn Hotel

(to be confirmed)
Monday afternoon. Brooklyn

Museum. Very good glass and little

visited by foreigners (or even New

Yorkers).

Tuesday 19th: Metropolitan Mu-

seum NY Roman glass, through

European to Tiffany.

Wednesday 20th: Free day in New
York, so much to see, so little time.

Thursday 21st: Fly to UK

Covered Casket with Tray, 1830-1840 from the Henry Ford

American members:

We very much

hope that some of our American

members will join us for all, or part,

of this trip, and pay accordingly.

Cost:
The final cost will be fixed

nearer the time, in case of exchange
rate fluctuations, (the $ is very weak

at present) but is expected to be
£1,850, double occupancy, single

supplement £410.

What is included:
The price in-

cludes all flights and coaches, but
not subway in New York. Accom-

modation. All museum admissions,

four dinners and three lunches. Not
breakfasts and other meals (America

does not do B & B as we know it)

breakfasts can be taken in the hotels,

or do as Americans do, breakfast

out. Nearby restaurants to the
hotels can easily be found and there

are no language barriers (well not
much), and some of us like burgers,

others don’t.

Insurance:
No insurance is includ-

ed, travelers MUST make their own

arrangements, particularly medical

and repatriation. Also ensure that
they are aware of any visa require-
ments. Visas are not currently

required for British citizens but you

will have to provide your passport

details in advance.

Bursery:
A little of your payment

will go towards a bursary for a

young museum curator to enable

that person to accompany us.

Glass Circle conditions:
£50 deposit will reserve a place on
a first come first served basis. This

will be fully refundable up to two
months before departure.

Booking:
Please fill in the form

below and send a cheque for £50 per

person to:- John P Smith , Chairman,

42 Vespan Rd., London W12 9QQ

Payable to The Glass Circle’

Contact:
email johnpsmi@

globalnet.co.uk

Full name

Phone

Address

Mobile

Post code

No. of additional members

1. Full name

2. Full name

I enclose a cheque for £50 per person as a deposit for

Glass Circle trip to USA Spring 2015. I understand

that I may not ask for a refund after 12th March 2015.
Signed

FUND RAISING

Thurscay October 30th 6.30 to 8.30

As The Circle continues

to be in discussion with

The Glass Association

about a possible merger

it has been decided

by the committee

not to put up the

subscriptions this year

as no joint decision on

future subscriptions of

a merged society has yet

been agreed. Should

we not merge, higher

subscription

levels

in the future will be
required.
However this means

that there will be a

shortfall in required

income to the Circle for
the year 2014/15.
We have decided to

hold a fund-raising
event so that those who

are able can help to
maintain the financial

stability of the Circle.

This will be in the

form of a champagne
reception at the Vessel

Gallery in Notting Hill

Gate. Vessel Gallery
is a leading gallery

for the showcasing of

contemporary

glass

and ceramics and we

hope that some of their

artists will join us.
The evening will consist

of a reception, gallery
talk, and raffle and will

take place on Thursday

October 30′ at 6.30 to

8.30

The Vessel Gallery,

www.vesselgallery.com

is at
114 Kensington

Park Road W11 and

parking is free in the

vicinity after 6.30.

I would like to attend this event at The Vessel

Gallery and would like to purchase

tickets

at £45 each.

I cannot attend but enclose a cheque as a

contribution to the Circle.

I hope/will not be able to bring along an item

suitable for the raffle.

I enclose a cheque for £

payable

to The Glass Circle
Full name

Address

Please send to John P Smith, Chairman, 42 Vespan Road London W12 9QQ

An auction of GLASS & glass-related items given by members

TO BE SOLD

is to be held after the AGM to raise
funds for future meetings.

Members are invited to donate items for

the sale and are requested to contact

VERNON COWDY

0208 653 4327

or
[email protected]

or alternatively bring their

donations PRIOR to the meeting

This meeting will befree
of

charge

BELOW LEFT:

fig. 7a

William Beilby
Goblet about 1765

BELOW:
Fig 7b

Wine glass about

1785

RIGHT:
fig.
7c

Jacobite wine glass

about 1755

FAR RIGHT:

fig. 7d
Privateer Wine

Glass about 1757
_

–

so pieces of glass that have been
collected over the last
5o
years go

some way to filling gaps in the
period of time between the end of

Cecil’s collecting and the present
day. The two most important

groups are from other collectors.

In the 197os, the gallery acquired

250 items of furniture, ceramics

and glass from the Handley-

Read collection. Charles and his

wife Lavinia were great collectors
of Victorian and Edwardian
decorative arts. The pair did the

bulk of their collecting in the

195os, when items by designers
such as William Morris and
William Burges were extremely

unfashionable. Derided at the

time, their collection is now seen

as nationally important.

Before their deaths in 1971,

Charles was planning for an
exhibition at the Royal Academy

which displayed his collection

stylistically; it was with that

in mind that we displayed his
collection at
The Higgins Bedford.

NEW GLASS GALLERIES

ceramics on which his collection

concentrated. In the glass

collection this is illustrated by the

items of Roman, Egyptian and
Medieval glass which allow us to

talk of the origins of glass, and the

small but excellent collection of

Renaissance and later European

glass,

including

Venetian,

German, Dutch, Spanish and

Bohemian. Then there is the bulk

of the collection, which includes

magnificent examples from the

golden age of glass’, including
enamelling by the Beilby family,

rare examples of Jacobite political

glass and Privateer glasses, (fig.
7abcd) as well as the three pieces

of Ravenscroft.

This unique foundation to the

museum meant that when it came
to redisplaying the glass collection
the bulk of the work
had been done by

Cecil himself. The

redisplay follows

the structure of

Cecil’s collection,

showing chrono-

logically the history

of lead glass from

continental influence

through Ravenscroft

to balusters and Bielby.

Once the structure

of the redisplays was

agreed upon, the

second priority was to

show as much of his

collection as possible.

As with all museums,

only a fraction of what is in

the collection is on display at any

one time, but with open storage

areas and large deep display cases
where the glass can be placed three

pieces deep the fraction has been

increased.
Cecil Higgins’ original col-

lection has never been added to.
It has always been felt that

the collection is so
representative in its
way, that adding to
it has never been a
priority. The imp or

cws Issue 135
Vol.
37
No. 2

NEW GLASS GALLERIES

lovely examples of Whitefriars but
their provenance is superb.
It is the stories of the collectors,

such as Cecil Higgins and Charles
and Lavinia Handley-Read,
which we have focussed on in
the new displays at The Higgins

Bedford. We are a collection of

collections, from Paleolithic flints
collected by Bedford’s Victorian

antiquarians, to watercolours of

John Sell Cotman collected by
the leading authority on his work.

We hope that through the stories
of these people, our founders and

benefactors, we are able to show
what at first may seem a disparate

group of objects as a cohesive story

of Bedford and the remarkable

gifts that these pioneering people

left to the town.

Victoria Partridge is Keeper of Fine

and Decorative Arts at The Higgins

Art
Gallery & Museum, Bedford.

The glass, which includes a

selection of fine Mid-Victorian

glass and Art-Nouveau glass

by GaIle, Tiffany and Zsolnay,
has been displayed in a series of
chronological cases exploring style

and technique (fig 8a & b).
The other major collection is

26 pieces of Whitefriars, which
came from the grand-daughter

of Harry Powell, the factory’s
chief designer. Powell kept the
pieces as a record of his work for

the company, so they are not only
LEFT:fig.

Emile GaIle Vase

about 1901

RIGHT: fig
8b

Louis
Comfort

Tiffany Vase about
1900

BELOW LEFT: fig.
9

Unpacking
Willem Jacobsz.

Van
neemskerk

engraved flask

about 1686

BELOW: fig.
10

Stripped out
building

Glass Circle News Issue 135 Vol. 37 No. 2

Ian

Freestone

BELOW LEFT:
Fig. I

Detail from

thirteenth century

stained glass panel,
now in the Music

national du Moyen
Age, Paris

TOP RIGHT:
Fig. 2

Reconstruction of

excavated window
from Khirbet

el-Mabar, Jericho

(on display in the
Israel
Museum,

Jerusalem)

BOTTOM RIGHT:
Fig. 3

Coloured opaque

glass mosaic

tesserae, found in

the glass workshop

at San Vincenzo al
Volturno, Molise,

Italy
STAINED GLASS

New light on medieval stained glass

through scientific analysis

this early period, the glass used

in both the East and the West

was made by mixing sand with

soda deposited around the edges
of lakes in Egypt. The glass was
melted in tank furnaces to produce

slabs weighing eight tonnes or
more, along the coasts of Palestine

and Egypt, where suitable sand

was abundant. These slabs were
broken up and the glass chunks

distributed around the Late

Antique world, to be remelted and
blown into table wares, containers

and windows.
By the 8th century, East-West

trade in the Mediterranean was

diminishing, and fresh glass

became less easy to obtain. It

appears that around this time,

glass workers in Europe began
to exploit the large amounts of

Roman glass which was available
in the ancient buildings which

were still standing. This was in

the form of windows and the

opaque glass cubes or
tesserae

from the mosaics on the walls and

vaults (fig. 3). For example, it has
been estimated that the Baths of
Caracalla in Rome contained over
zoo tonnes of window and mosaic

glass, none of which remains and
presumably has been recycled since

Roman times. The window and

vessel glass found when excavating

the 8th century Abbey at San

Vincenzo al Volturno, Molise,
Italy seems to have been entirely
derived from Roman glass made

some Soo years previously, and
obtained through the gift to the

Abbey of a Roman building which

was used as a source of building
materials, including also columns

made of the famous Egyptian

tained glass as seen in

our great cathedrals

and churches (fig.

1) emerged in 12th

century Europe, but its origins

lie much earlier, in the middle of
the first millennium AD. Shaped
pieces of blue, green and yellow

glass, along with glass streaked
with red, have been recovered
from archaeological excavations

across Europe, for example in
the monastery church at Sion,

Switzerland dated to the 5th

or 6th centuries, and in Jarrow,

Northumbria, dated to the 7th

century. Coloured window-glass

was also used in the Near East, for
example in the Islamic palace at

Khirbet el-M4ar, Jericho, where

it was held in place with plaster
(fig. 2), rather than the H-shaped

lead
cames
familiar in Europe. In

Glass Circle News Issue 135 Vol. 37 No. 2

STAINED GLASS

granite from Aswan, on the Nile.
The window-glass fragments
excavated at San Vincenzo are

frequently coloured blue but a
range of colours occur. As can be

seen from the fragments in fig. 4,
they are sometimes streaky, due

to the mixing of coloured opaque

mosaic tesserae with colourless

glass to make translucent glass.
Clearly the remaining Roman

glass could not indefinitely sustain

a substantial production, because
by the end of the first millennium

AD northwestern Europe had
begun to make its own glass from

local raw materials, and this is

very different in composition
from Roman glass. The new glass

was made by fluxing sand with
the ashes produced by burning
forest plants, such as beech trees

and bracken. Medieval authors

such as Theophilus and Eraclius
tell us that this was the case, and

chemical analysis confirms it.
Medieval glass is a type known
as potash-lime-silica glass and

is also rich in the oxides of
magnesium and phosphorus,

which are important components

of wood ash, along with calcium

and potassium oxides. A key
difference between the two glass
types is the content of silicon

dioxide, or
silica,
which is typically

15% higher in the Roman glass.
Silica, which is derived from the

sand, forms a strong cross-linked

network in the glass structure
— it is what makes molten glass

stiff and viscous and allows glass
to form. Unfortunately silica is

also an important contributor to

the durability of the glass — the
more silica, the better the glass

stands up to the damp climate
of the North. The low silica
contents of medieval glass mean

that it is easily damaged by rain
and condensation and this is

the reason why medieval glass is

frequently less well preserved than
Roman glass which is a thousand

years older. Large European
cathedrals such as Canterbury and

York have their own specialists
working on the conservation of
their stained glass windows, and

major programmes, such as that
currently underway on the Great

East Window of York Minster,

are undertaken to ensure they

are properly protected. Thanks
to a research grant generously

awarded by the Leverhulme
Trust, we have been able to work

with York Glaziers Trust and

other conservation studios to

sample glass in their care while it

was removed from the supporting
leads for conservation (fig. 5).
Medieval stained glass windows

are characterised by their vivid
colours but these colours are not

‘stains’ as we might assume from
the term. Most coloured glass was

not stained on the surface, but was

coloured throughout, by dissolved
metallic ions such as cobalt
(blue), iron (yellow or green) and
manganese (a purplish brown

known as’murray’). Glass coloured

throughout from the melting pot

is sometimes termed ‘pot metal’

glass. A technique known as ‘silver

stain’ was introduced in the i4th
century whereby silver salts were

painted on the surface of the flat

glass sheet and reacted with the

glass at high temperature in a kiln.
The silver diffused into the surface

and formed a thin yellow layer, or

stain. The development of colour

seems to have been one of the key
challenges facing the glassmakers.
For example, in the izth century

it appears that European sources
of cobalt, needed to produce the

beautiful deep blue glasses of

the windows, were unknown.

Chemical analysis shows that the

blue glass in the windows of this
time, such as those of St. Denis

in Paris and York Minster, was

produced by mixing old Roman
mosaic glass and contemporary

potash-lime-silica

glass,

continuation of the early medieval

practice seen at San Vincenzo. By
the 13th century, cobalt appears to

LEFT:

Fig. 4

Coloured glass sheets

from San Vincenzo.

RIGHT:
Fig. 5

Project researcher
Jerzy Kunicki-

Goldfinger and York

Glaziers Trust
Head

of Conservation

Nick Teed sampling

a panel of the Great

east Window,
York

.Minster, while

it is undergoing
conservation.

Glass Circle News Issue 135 Vol. 37 No. 2

•

•
STAINED GLASS

•

•
LEFT:
Fig. 6

Nanoparticles of

metallic copper in

a translucent red

glass. The scale
bar in the lower

right is divided

into 5 units, each

of 100 nanometres

(1 millimetre

= 1,000,000

nanometres).

ABOVE:
Fig. 7

Cross section of a

fragment of 13th
century window

glass, showing
the characteristic

striated structure

ABOVE RIGHT:
Fig. 8
Cross
section

of 15th century

window glass,

showing a single

layer of red.

have been discovered in Saxony,

and the blue glass produced using
mosaic tesserae disappears.

The colour red also posed

difficulties.

Medieval

glass

makers found that they could

develop a translucent red glass

(sometimes termed ‘ruby’) by a
technique known as ‘flashing;

whereby a gather of red glass on

a blowpipe was coated with white
(colourless), then inflated into a

cylinder comprising a thin layer of
red over white. This process was

essential, because the red colour

was imparted by tiny nanoparticles

of copper metal in the glass (fig.
6). If the red layer was too thick,

the glass would be opaque and

unsuitable for windows. We have

found that there was an abrupt

change in the technique used to

produce the copper nanoparticles

at around
1400
AD. Before this

time, red glass in England and

France was ‘striated’, consisting of

a large number of extremely thin

layers of red between thicker layers

of white (fig. 7), while after this

time there was a single red layer

(fig. 8). Our research has found
that the striated red layers were

not produced by repeated gathers

of glass, as is sometimes suggested
in the literature. Instead the

glassworkers produced a streaky

glass by mixing a blue copper-
bearing glass and a colourless glass

in a melting pot. The blowing of

a glass cylinder stretched these

layers until they were relatively
thin. Then a heat-treatment

caused diffusion of copper from

one glass into the other and the
precipitation of nanoparticles to

give a series of very thin red layers,
close to the boundaries between

the two initial glass types. From

around
1400
red glass was made

using the standard flashing

technique, a procedure which has
been in use ever since.

There is written evidence that

much of the coloured glass in

English windows was imported

from the continent. For example,

in
5
449,
John Utynam, a Flemish

glassmaker, was granted a
monopoly to make coloured glass

by Henry VI ‘because the said art

has never been used in England’.

Written sources on white or

colourless glass are limited but

the fact that continental glass was

sometimes specified suggests that
colourless glass was also produced
in English glass houses. We have

found that from around 137o, a
new type of coloured glass was

introduced into English windows,
with higher lime and lower potash

than earlier types. The new

coloured glass appears to be from

the continent but the colourless

glass continued to be made to the

old recipes. Is this English glass?

It very much looks that way, as

it is very close in composition

to glass made in English glass

houses in Staffordshire. We are
currently working to confirm

a Staffordshire origin using a
series of tests involving isotopes

and trace elements. The Weald

has traditionally been assumed

to be the major source of glass

in medieval England. It may

well emerge that the output of

Staffordshire was on a similar

scale.

Ian Freestone is Professor of
Archaeological Materials and

Technology at the Institute of

Archaeology, University College

London, where he teaches

and researches the science of

archaeological

and

historical

materials.

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Glass Circle News_No.135, Jul 2014

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