George Eastman's Original Coating Method - US Patent 226,503

One of George Eastman's earliest (?) patents was for coating glass plates by running them, upside down, across a roller half-submerged in emulsion. After passing the roller the plates were flipped right-side up to dry. See here. The roller continually lifts emulsion up as it rotates and transfers emulsion to the plate; thickness being determined by (amongst other things) viscosity.

This seemingly simple technique is all but forgotten, no? I'd be curious to hear anyone's thoughts about it.

If you go antiquing frequently, you've undoubtedly come across those old porcelain envelope moisteners (see picture). These embody the same basic idea and indeed, I'm wondering if they wouldn't work for coating rolls of film, if modified somewhat.

Just throwing this out there..

Some of us have seen the Ilford plate coating line in action, a far better system and modern but relatively easy

Ian

Have to wonder if this wouldn't work for wet plate..

So, I'm assuming the plate was ran across the top of the roller while the inside of the "base" (for lack of a better word?) was filled with an emulsion?

Sorry. My brain's fried. But I cant imagine a glass plate going on the bottom part of the roller since glass isnt very flexible (I know from experience)



ETA: didnt realize you posted a link

That envelope moistener only holds 3 or 4 tablespoons full of water when it's filled to capacity.

Build a trough out of stainless steel with a water jacket around it and mount a high-quality rubber roller in it, ideally connected to a small motor.

Or heck... operate it by foot treadle...

One drawback clearly is that you cannot use up the emulsion. Fine for "mass production" but a waste for small batches.

holmburgers said:

This seemingly simple technique is all but forgotten, no? I'd be curious to hear anyone's thoughts about it.

Click to expand...

A simple technique, but not forgotten. A quick search will turn up any number of links to companies producing small coating machines. Most are aimed at specialist labs needing repeatable coatings on an assortment of substrates. The same idea is also used in the electronics industry for soldering components to circuit boards.

I have trouble getting consistant defect free coatings when I make glass plates, and have considered a roller. Cleaning and wastage put that idea to bed, but I've also considered spin coating as a potential answer.

paul_c5x4 said:

A simple technique, but not forgotten. A quick search will turn up any number of links to companies producing small coating machines. Most are aimed at specialist labs needing repeatable coatings on an assortment of substrates. The same idea is also used in the electronics industry for soldering components to circuit boards.

I have trouble getting consistant defect free coatings when I make glass plates, and have considered a roller. Cleaning and wastage put that idea to bed, but I've also considered spin coating as a potential answer.

Click to expand...

i can't remember where i read it,
but martin reed who wrote the book on silver gelatin said
that his best plates were the ones that were totally submerged.
i was thinking of filling a small tray with emulsion getting wires on all 4 corners of my glass
( to lift up, lay down the plate ) but it seemed like a huge mess. a sponge brush always seemed to give me the best coat.

john

Hi All,

Apologies for butting into a thread that is exploring different options. Options are always good -- as is any discussion that explores them. In this case though, at least for glass plate coating, the answer is dead easy, dirt cheap, and absolutely reliable. http://www.thelightfarm.com/cgi-bin/htmlgen.py?content=03Nov2011

The emulsion flows and sets along all edges of the plates. To that effect, it works likes Martin's technique of submerging the plates, but without the waste and mess. Also, it gives very even coatings -- something that is hard (or impossible) to achieve if the plates are moved at all between the pour and set-up.

I've been coating film every other day for quite a while now. That one is a little more difficult, in that it takes some (low tech) equipment and practice, but it's very doable. I've got a lot (probably way too much) about it on The Light Farm, but here's some info on having a very good tool made. http://www.thelightfarm.com/cgi-bin/htmlgen.py?content=06Jan2012

Also, PE's 5-in emulsion blade is very good for film coating, but it's not being sold anymore. I don't know his plans for it, but perhaps more are in the works. He talks about it like it is (is going to be?) a readily available tool.

d

Honestly, I can't say if this is a practical method in this day and age, but I'm glad you guys are sharing your thoughts.

I do wonder how "low you can go", in terms of minimum quantities of emulsion. You could use up the remainder with one of the tried and true coating methods though.

Imagine though if you had a continuous web of film that you could run over something like this, and then afterwards you could introduce a twist into the film to bring it right side up.

Or, you could just have the leading end go up... then back.

Hello All,
" Any suitable material", So reads the patent. I think that the success or failure of this kinde of gizzmo would depend on the surface characteristics of the roller. Having worked with coatings rolled on via multi roller machines, the interaction between the coating and the roller is crucial to how the coating is deposited on the substrate. Varrious synthetic "rubber" materials are used. I think that George probably knew, from experience, what kind of rubber worked best for the emulsions of the day, but considered that proprietary info.
Bill

One thing I have seen described in a few places is a counter rotating roller followed by a meyer rod to precisely control the thickness of the coating. The meyer rod is suspended over the trough so that any runoff is caught and reused.