Monday, June 20, 2011

8 x 15 plate coating

How I coat 8x15 inch glass plates with Liquid Light emulsion. Single strength glass was used from the glass store. I had them polish the edges. The glass fits into a book form plate holder for a Vageeswari camera.

Double strength glass is thicker than single strength glass. I had some and cut edge strips out of it. They should be at least 4 inches wide, two are longer than the others. The sharp edges were taken down with emery cloth. Wet o dry paper would be better to use wet.

The thinner single strength 8" x 15" glass photographic plate was cleaned with Calcium Carbonate and Everclear grain 151 proof alcohol. It was rinsed with tap water, held with paper towels, and wiped off. It was then cleaned only on the top with Everclear. It was handled carefully using paper so as not to touch it at all with bare fingers.

The plate was laid out on a flat table on a sheet of rubber matt. The thicker glass edge strips were laid out around it with 1/8th inch gaps between the plate and the edge pieces but without a gap between where edge pieces touch each other.

Buttermilk was used in daylight to see how much emulsion it would take. 2 1/2 ounces did the job. Buttermilk is very much like emulsion and cleans up easily. One 35mm film canister holds about an ounce of emulsion if it is totally full. Nevertheless, I used three full canisters of Liquid Light emulsion; it is better to have some left over than to not have enough.

Three cold and solid full 35mm film canisters loaded with Liquid Light emulsion are placed into a quart measuring cup that is filled with 120 degree F water to melt. A 'nose' pot and a glass "puddle pusher" rod are placed into a tray with hotter water in it so they can warm up. When things are taken out of the water they are dried off and they quickly cool. The water in the measuring cup cools to 110 F; the top is taken off a canister and the emulsion is checked with the thermometer probe to see if it has melted completely.

In the dark, with an amber light on, the emulsion was poured first into the 'nose' pot, after it had been dried, then out onto the plate in long s curves with little spaces between the runs. The emulsion was pushed from one or two inches inside the plate out towards the near narrow end to start and make sure that end was fully covered. Then, I started the scrape out on the thicker edge piece and pulled the rod slowly and lightly all the way to the other side. One swipe did it. Excess emulsion piles up on the wide edge piece.

I was lucky the first time and the plate covered completely with one swipe. However, the second time four swipes were needed; good thing it was hot. The excess was push back onto the plate and dragged to the other side. Three cans were almost completely used up. It is best to do it in one pass. Multiple passes creates uneven exposures. Use one application no matter what. Uneven application, as in pouring, can be remedied if the glass is heated like when I put hand poured smaller plates onto heated stone to allow uneven cooling emulsion heat back up and spread out. 4 canisters in a small measuring cup may be better because it comes out faster and 3 didn't cover on the third attempt at coating a plate in one swipe.

Excess and spillage soon gelled and was taken up with a new razor blade, and an artist's palette knife, and returned to an empty film canister.

The plate looks great. It was set onto three wooden dowel rods in a cardboard drying box of shelves. The wet back would stick to the paper and be very difficult to remove otherwise.

This method is very easy to do and gives excellent results. The edge pieces and rubber mat and glass rod may be used over and over. Actually, a glass rod isn't even needed I bet. I'll need to use a flat piece of glass with a polished edge to coat larger plates because a longer one is needed to cover and I don't anticipate any different results. The glass strip can even be heated first and that will help. Glass on the rubber matt was room temperature. It coated great. I'm happy.

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