I spent Friday resting and working at the golf course, but as the class elected to have a lecture-free work day, no crucial notes were missed. Today I finally brought my camera, so my posts will be supplemented with photos, which I think make for better notes anyway.
Begin with a clean plate. Mark out the image area in pencil. It is best not to draw the actual line in pencil, as the gum tends to follow the graphite. Instead, mark the end points. Elevate your straightedge, either by cantilevering it on top of another ruler or by taping coins to the bottom. A straightedge which is flush with the plate will cause a smeared line as the gum will ooze under it.
Fill a ruling pen with gum arabic (you can use tapem or 50/50 if you're careful during washout. the advantage of this is a hot border cuts down on marks and spots, as it burns them out, leaving a cleaner border). Use an eyedropper, and make sure the ruling pen is free of debris before beginning.
Test out the line on the border of the plate, adjusting the line width and flow. Too thick of a line and you may run out of gum before reaching the end, creating an uneven line.
Using only the weight of the pen, draw along the straightedge, ending a little past your mark. Repeat this for all four edges. The goal is a razor straight edge and sharp corners. (obviously, this would be easier, and probably more accurate, with a photo plate, but as photo plates are becoming scarce, it is best to know the hand method as well.)
Widen the border carefully with a small brush. Starting immediately with a large brush can be dangerous for the line edge. Pour gum directly on the plate to create a little pool to work from.
Widening again with a larger brush.
Finish with a sponge. Let the gum border cure for about an hour.
When border is dry, pour on a little shellac, buff in tight with a cloth. A slightly heavier shellac film is good for a flat, as it needs more ink. Bake the shellac in at 250 degrees for 5.5 minutes. Test with a white cloth and a little lithotine. If a slight color comes up, this is acceptable, and even makes cleaning easier. Too much color means the shellac isn't cured, and you should put it back in the oven for up to a minute.
After the shellac is cured, buff in a layer of asphaltum.
Wash out the gum border. If you used tapem, be every careful not to get any of the gum on the image area, as it will leave a faded mark in the flat. It's best to stop while you're a little ways from the image edge and use the roller to get the rest.
Roll up with a medium bodied ink (shop mix) until full and velvety.
Apply an even layer of talc.
Buff in a thin layer of straight tapem. this acts as an etch and is a shortcut to etching through a mask, which isn't really necessary for a flat. Let the etch set for at least an hour before further processing.
We also had a couple of mini-demos/lectures. The first was about breaking in sponges.
The nicest (and of course, most difficult to procure) sponges are photographic fine pore sponges. The finer the pore, the more evenly the sponge distributes water across the surface.
Remove the sponge from the wrapper and round the edges. The more care you take in rounding the edges, the longer lifespan the sponge will have. Remove the sizing by soaking and squeezing out the sponge, never wringing it. The twisting motion breaks down the sponge faster, makes it more susceptible to shedding. If you don't remove all the sizing, it will break down your etch when you use the sponge. Dirty sponges can be cleaned by dissolving a little magnesium carbonate into a bowl of water and soaking an squeezing the sponge as before. Clean sponges = clean prints.
I'll save the little chemistry lesson on gum arabic for a slower day, my fingers are hurting. For now, I'll leave you with my two favorite rodney quotes of the day-
"i'm only human. sometimes i fuck up"
"basically, it's a bitchin acrylic matte medium"