Topic: Zwischengold salt 1700's/1800's early pressed glass?

[flying free]

Sorry, I have looked for the Corning research ( which I know is on the site somewhere and I know they are researching what the red was made of and what the glue is, in order to conserve one of their pieces) , but I cannot find it again now.  I find their site extremely hard to navigate and can't think where I would have found it before.

m

[oldglassman]

 These may be of interest , currently on offer .
eBay item number:282692155682

cheers ,

Peter.

[Paul S.]

the red staining seen in my salts reminded me of the shade of a microscopy stain we used many years back which is/was called mercurochrome  -  it's a bright red/carmine colour and was a stain used commonly in entomological preparations.                  Very thin and penetrating.
I suspect it has been around for years  -  just a thought.

[flying free]

I don't think this was the research I'd come across before (I thought that was more recent but could be wrong), but this piece  of research appears to date to 1980 and is very interesting.  It's worth reading the whole report however -

See page 28 of the report for a description of the red coloured vehicle on the back of the gilt or silver decoration of the medallions

https://www.cmog.org/sites/default/files/collections/85/8595D55B-378A-4400-91C2-B7D20E08F616.pdf

page 28
'...The red pigment is dispersed throughout its
vehicle as fine particles having a strong, pink,
transparent color. They can be seen at magnifications
of -40 X . The color of the particles at a
microscopic level is better described as "rose"
than "deep-red," although the latter is an accurate
description of the color of the film in bulk....'

and

'... Two possibilities considered for identification
of the red pigment were dragon's blood and rose
madder. Dragon's blood seemed a likely choice,
because it is traditionally thought to have been
used as a red varnish in association with gold
decoration. While it has not been strictly eliminated,
it now seems unlikely that the red pigment
is dragon's blood. Samples of modern dragon's
blood, in the form of an orangish-brown resin,
transparent in small pieces, were found to be
soluble in ethanol and unaffected by dilute aqueous
sodium hydroxide solution. In both these
features it is unlike the red pigment under investigation.
In addition, the orange-brown color ofthe
modern dragon's blood under the microscope is
distinctly different from the characteristic rose
color of "the unknown."
In contrast, however, the microscopic appearance
of the pigment from the Zwischengoldglas is
virtually identical to that of a pink powder found
in a small Egyptian glass bottle of Roman date.
While that seems an unlikely place to look for a
parallel, that powder had previously been identified
as rose madder by one of the authors (Robert
Brill). Particles of the two pigments have exactly
the same color, transparency, appearance under
ultraviolet illumination,14 lack of birefringence,
and more-or-less indefinite shapes. Having not
come across evidence to the contrary, we proceeded
on the assumption that the red pigment is
rose madder, although there are in fact other
candidates. Red gum accroides, which seems to
match at least some of the properties of the Zwischengoldglas
pigment, is one. The yellow form of
gum accroides has been used most frequently as a
yellow dye, along with gamboge and saffron, to
produce "gold" varnishes for bright metal surfaces
such as tin foil and silver. Much less known is a
similar use for the red gum. This resin is thermosetting,
obtaining greater hardness and becoming
virtually insoluble upon hardening. Furthermore,
it is totally soluble in aqueous sodium hydroxide
solution. Mixed with shellac and spirit alcohol, it
frequently saw use as a red varnish stain for metal.
The lac dyes are another possibility. '


Under the section headed 'Summary of results' on page 33 it is stated:
'5. The red pigment is probably rose madder. '

However, this relates to investigations on a variety of zwischengold glasses and they provide a list of the objects at the beginning of the research.  There is no mention of small glass bowls with applied metal and coloured sandwiched decoration (i.e. what I have suggested are zwischengold salts).
m

[flying free]

To add to the information in my post above -

Winsor and Newton have this to say about Rose Madder

Ref source: http://www.winsornewton.com/uk/discover/articles-and-inspiration/spotlight-on-colour-rose-madder


'Rose Madder is a distinctive rose coloured pigment made from the roots of the common madder plant, Rubia tinctorum. It is a transparent pigment with granulating properties in Water Colour. A natural organic lake pigment, it was first used as a dye for fabrics. Evidence of its use can be found in ancient Greek, Roman and Egyptian cloths as far back as 1500 BC. Cloth dyed with madder root pigment was even found in the tomb of Tutankhamun. Considered the most stable natural pigment, it was very sought after and was brought to Europe by the crusaders. By the 13th century, it was being cultivated across Europe, notably in the Netherlands as their sandy soil provided a favourable environment for the plant. 
  (my bold - I thought this was interesting  for a particular reason - please see my notes at the bottom of this post)

However, the production of madder dye was costly and by 1860, Great Britain was importing madder at the value of £1.25 million a year. It was necessary to find a better, more reliable method making of the pigment. The renowned colourist George Field made extensive study of the madder plant and in 1804, discovered a more efficient process of extracting the dye and making a stronger, more vibrant pigment. William Winsor understood the importance of George Field’s research and acquired Fields’ notes and experiments following his death in 1854. These 10 volumes formed a basis of some of the colour recipes for the then newly founded Winsor & Newton Company. 

The production of Rose Madder is still based on the recipes of George Fields, which Winsor & Newton have exclusive access to and remains a unique pigment with varying shades of rose, browns and purples that cannot be duplicated. Though alizarin (a dye derived from madder) was later synthesised in the 19th century making it far more affordable, the two colours should not be compared. Rose Madder retains a soft depth and richness unlike any other rose available.
Available in Watercolour and Oils, Rose Madder is an excellent glazing and watercolour pigment. Artists such as Jan Vermeer, J. M. W. Turner, Constable and Holman-Hunt and James Abbott Whistler have used the unique pigment to great effect.'


Notes: 
I bolded the sentence above relating to the Netherlands because of the coincidence of me writing in my original post:
 
' 'Raymond Slack,English Pressed Glass says of pressed glass
page 13
'There has been considerable controversy as to whether this process originated in America or Europe. ... However the man often credited with the invention of pressed glass, the American Deming Jarves of the Boston and Sandwich Glass Company, himself acknowledged the European origins of the process in his Reminisces of Glass Making published in 1865:
"Although it has been commonly believed here that the invention originated in this country, the claim cannot be fully sustained.  Fifty years back the writer imported from Holland salts made by being pressed in metallic moulds and from England glass candlesticks and table centre-bowls, plain, with pressed square feet, rudely made, somewhat after the present mode of moulding glass."  '

That would put the date at c.1815, and in fact we know that articles with pressed square feet were being manufactured in this country at the end of the eighteenth century.' 

m

[Robin G]

Thanks for ebay alert. They also used the word eglomise. Here are some of my salts of this type. Does anyone think the big rock with the boats is Gibralter? Of the portraits, I've found more men than depictions of women. They seemed to love those parasols. Interesting notion that there was a copybook for these designs. Any source examples?

[flying free]

is it possible to upload your pictures as 600 x 400 pixels as it's impossible to see the detail at the current size.
I love the one at the bottom - great picture.

What was the reference source for there being copybooks of these designs? 

I have seen somewhere that they were sometimes produced as  marriage salts (so man and woman pairs).

m

[Robin G]

So sorry I haven't got the hang of how to post photos. Seems a waste to post each pic separately but maybe that's the only way to get them large enough. This will show a gentleman entering an estate.

[Robin G]

Another "doppelwand", or zwischengold salt, that has a red background when looking into the bowl, but when seen from the reverse, looking at the flat disc, it appears more green. BTW, when I resize to 400x600, I get a warning that the file is too big to post.

[Robin G]

Salt, probably Bohemian, showing a rock plus boats