How Did They Clean Glass For Commercial Plates?
Hello to all,
Glass cleaning has been discussed thoroughly on this forum. I have my own procedure that I have published on Denise Ross's Thelighjtfarm.com . Whatever the cleaning procedure one uses, I think that a piece of glass should be able to hold a vertical sheet of water without breaking up or beading. It seams reasonable that a surface that cannot sustain a sheet of water cannot support an aqueous emulsion or solution.
Sometimes I get an entire batch of glass that will not hold a vertical sheet of water no matter what I do. Adding a wash in ethanol has no effect. Even a micro-etch in NAOH
will not help. I conclude that my entire batch of glass is not usable due to something inherent in the glass.
I remember,years ago, running across a publication from KODAK discussing the quality of glass required for dry plates.
I wonder if anyone is familiar with any glass "standards" employed by the old glass plate manufacturers.
P.S. Coating with only IR light is a great big PAIN. Poor depth perception! I have a hard time finding the middle of the plate!
I think you will find that many glass plates refuse to allow water to sheet on them. That is what surfactant is for. A small amount will go a long way. And, there are 3 types of surfactant. They are Anionic, Cationic and Non-Ionic. Photo Flo 200 and the Tween family belong to the latter. Triton X 200 anionic.
I take your point. All my Emulsions contain ethyl alcohol and most contain some Triton X200. But the vast majority of of glass I use dose sustain a standing sheet of distilled water until the water evaporates..
I have noticed that most antique boxes of glass plates contain glass that is low in green color, compared to today's standard plate glass. This indicates lower Iron content.
I do find it interesting that any sheet of glass which will hold a vertical sheet of distilled water NEVER,EVER frills upon processing.
There are two sources of easy-to-access info that I know about.
1) Photography with Emulsions, by W. Abney, 1885, starting on page 114. It's available as a Google book from the TLF lit list, #5: http://thelightfarm.com/Map/Literatu...eListPart1.htm
2) Wall's 1929 Photographic Emulsions. p.162.
And, though I feel like a broken record, I don't support the use of a surfactant in emulsions coated on glass. The times I tried were the only times my coating failed miserably. You're not using gelatin, so of course your situation might be different, but a reminder anyway.
Thank You Denise,
I was particularly gratified that W. Abney specifically confirmsthe importance of a standing sheet of water as a test for cleanliness of glass plates. I have sulfuric acid (Wall) and will get some Nitric acid (Abney). But really, the acid/base cleaning method is very similar to the way in which I already clean glass. But I use oxalic acid and phosphoric acid, at different times.
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W.Abney also points out that many emulsions have been dismissed and discarded because they failed to adhere to dirty glass.
Bill - If you're going to be using sulfuric, look for a lab supply place and get some stuff called "NoChromix" - http://godax.com/
You add a packet of the stuff to conc. sulfuric acid and then you just soak the glass in the Nochromix/sulfuric solution. It will clean most everything off glass - given enough time. We used to use it in a lab I worked in as a replacement for dichromic acid/sulfuric acid solution which was the traditional lab glass cleaning solution.
Plan ahead and let your glass soak and you'll never have to scrub glass again.
For up from the ashes, up from the ashes, grow the roses of success!
Part of the question in your OP referred to the quality of glass required for dry plates. That question has rumbled around in my brain for years, but never floated high enough to prompt the necessary lit search. Thanks for the prompt!
There's not much information. I think it's because glass technology is one of those areas most of us take for granted. But, it has changed considerably since gelatin emulsion was first poured on glass. At any point in the timeline, photographic companies used the best glass-for-the-price available to them. In the 1930 edition (English translation) of 'La Technique Photographique', L.P.Clerc wrote:
"The glass used in the manufacture of photographic plates is specially manufactured, and is, in fact, the monopoly of certain Belgium firms. It must be fairly flat, of uniform thickness, almost colourless, and as free as possible from bubbles or black spots. These qualities are rarely united in one glass, even in the highest qualities for picture framing, which are of much better quality than window glass. The sheets of glass, received in crates, are sorted according to thickness and quality, and stored for distribution as required." p152.
It's unclear what technique(s?) were being used to make the glass.
In Clerc's 2nd edition (1937/1946 reprint) he added a footnote: "Drawn glass, which is now beginning to be more widely used..."p157. According to the Wiki machine, 'drawn glass' (Fourcault process) was developed in Belgium in the early 1900's. About that time, machine-rolled glass became more available. It was cheaper than hand-rolled glass, but the initial capital investment was huge, and only a few companies were involved. Float glass, which is probably all most of us recognize as sheet glass, wasn't invented until the 1950's.
Back to the issue as far as artisan emulsions are concerned -- any green color a glass plate might have won't be a problem worth noting for colorblind/'ordinary' or ortho emulsions, and might even be to a slight advantage.
Glass making has changed considerably in the last 100 years. When I was young, window glass had quite a few bubbles and images "rippled" due to thickness variations, so I see the logic in what Denise says - for glass made 100 years ago.
Virtually any good glass today is superior to anything made 100 years ago, and probably even 50 years ago. I used ordinary window glass cut at my hardware store and it worked just fine. The Formulary now supplies 4x5 and 8x10 glass plates for coating.
I should add that Mark Osterman of GEH uses window glass, also with great success.
Sorry, Ron. I don't grasp your point. What logic of what statement? I use the cheapest glass I can buy. Modern glass is great stuff. If it happens to have a green color cast - no matter. It's what I have always advocated on TLF.
Originally Posted by Photo Engineer
(btw: You might consider reading TLF sometime. Good rag if you are interested in making antique artisan emulsions.)