From: Monnoyer Philippe (monnoyer@imec.be)
Date: 08/27/02-03:52:54 AM Z
Hello Margery,
I am an emulsion maker and I used to coat my glass plates manually with very very high regularity. This is very simple, but one has to know the tricks. First, the plate has to be levelled on your bench, at ambient temperature. The temperature of your liquid emulsion matters. Mine was above 34°C (94°F).
You need a coating rod. I used stainless steel coating rod winded with a wire. The diameter of the wire determines the quantity of emulsion you let on the plate when scraping. You need a wire diameter of about 85 mils to coat a wet layer of about 100 microns thick.
You put 2 to 3 milliliters of "warm" emulsion with a syringe along one border of your levelled plate. You immediately scrape it with your winded coating rod accross the plate (do not turn/roll the rod when scraping). Rince your rod in warm water before another coat. Then, you do not touch the plate and let the emulsion set for at least 3 minutes. The emulsion is set when the layer reacts as a solid under the action of the tip of a knive or pipet. After that setting time only you can take your plate and put it in a dustfree dark area where it will stay overnight or even a bit more, for the drying time. During that time, the emulsion losses its water to give a dry, ready-to-use emulsion (it is dry when it does not stick anymore to the finger). You can warm the drying air a bit, but not above the melting temperature of the set gel, otherwise you will end up with a melted ugly coating. That melting temperature is very often close to the ambient temperature. My advice: dry at ambient.
As you are coating metal, which has a higher calorific capacitance (is it the correct english spelling ?) then glass, it might be that the emulsion sets to a gel too quickly before you finished the scraping. If it is so, warm gently (and uniformly !) your plate before the coating. This will bring you to longer setting times after coating.
You can buy coating rods at http://www.rdspecialties.com It is cheap and very effective. I would recommend the 85G (gapped) for your application.
Coating is almost an art ... ;-)
Philippe
Belgium
-----Original Message-----
From: Margery [mailto:margeryfranklin@att.net]
Sent: Monday, August 26, 2002 16:32
To: Alt Processes Llist
Subject: fake tintypes
Nothing as interesting as when is porn porn, the meaning of postmodernism,weston's peppers and the value of contemplating women's breasts. Just a mundane inquiry: I am trying to coat the metal plates supplied by Rockaloid with Ag Plus emulsion. They recommend pouring a small puddle onto the middle of the 4x5 plate and moaving the plate around so the stuff is distributed, and using a finger to push it toward the corners if necessary. Using a finger doesn't work at all for me-- and I am not getting anything resemble even coating although the emulsion is liquified as per instructions.I've tried a foam brush an d hake brush too, with very messy results. I'm new to liquid emulsions -- are some better than AG Plus for working on metal? or paper? All responses much appreciated.
Also -- could someone reind me about how one accesses the list's archives? Thanks.
Margery
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