One shot dose is advisable for lots of reasons. But I suggest, especially
in early learning stages, use drops, not ccs. The gum arabic is viscous &
hard to measure accurately in small quantities, even I suspect with
syringes (tho I haven't used them yet).
We keep gum-14 and the ammonium dichromate in separate brown glass
dropper bottles. A total of 40 drops will do about two 4x5s, depending
on porosity of the paper. A total of 100 drops is more than enough for a
12 by 16 on medium paper. That way you can adjust as you go along.
Besides, the emulsion changes once mixed. If you have more than you use
within, say, an hour, results won't be the same anyway. You think
counting to 100 is awful. It isn't, goes very quickly, easier than washing
graduates (or undergraduates anyway). Also, for large amounts, do by
squirts -- a dropperfull at a time. Note, for figuring: 20 drops of most
of these liquids equals one cc. Check your particular droppers by dropping
whatever into a graduate.
This is all, by the way, amply covered in the archive!!!!! (Along with
much else!!!!!)
> "Despite what some people will tell you Arches is not a good paper for gum
> printing unless you size it first. Did you size it."
You can't just say "arches." You have to say *which* arches as they have
probably 50 individual papers. One I have with the watermark "arches
france" doesn't clear no matter what I do to it, or how many coats of
size. Some others work better. But no matter what worked last year, these
papers do change -- were they factory sized summer or winter, for
instance. Makes a big difference. Also, their batches of lintner or
whatever they're using at the paper mill change. As do their water
supplies. Etc. Etc. Some people try a couple of sheets of a new lot of
paper, then if it works, and they like it, go back for a big supply
from the same batch. However, I have never found any Arches a paper of
choice for gum.
Contrary to what a certain Terry King, also I believe on this list, may
tell you, we have had superb results with Rives BFK. It's possible they
get inferior stock in England, or maybe the water there affects it badly,
or perhaps it's all that gloy. We however often do a coat or two with no
added size. After that the factory size has started to wash out & it will
need more. (And whoever has announced that papers are sized at the factory &
don't need further sizing for gum, let alone multi-coat gum, gets a PhD in
mouthing off theory.)
This also is well covered in the archive.
However, note that the more you gelatine size (and in my experience
two gelatine coats at a time to start make the paper too slippery) the more
exposure you'll need to keep the highlights (shadows too for that matter)
on the paper. In other words, what lets the unwanted stain release, also
lets the whole business release. My experience is that with any kind of
added size (gloy, too) I have to use MUCH thinner coats. (That's one of
the rules for my soon-to-be-famous one coat gum: little if any added size.)
> "Prepared gum goes off after a few days, it is better to use fresh
> each time."
Prepared *emulsion* goes off, as noted, quite promptly. Commercially
bought lithographers gum 14 doesn't go off. It comes with some deadly
preservative already in it (mercury or whatever).
> 1. the gum never "set up" when I mixed the dichromate into it. (it
> never thickened)
Not supposed to, if you're using liquid gum arabic.
And for black, try Rowney Gouache Jet Black. Comes in a large tube.
Strong covering power, clean whites. One of the reasons lamp black is
problematic is that the particles are so fine they burrow into the paper
& don't release. but it can be used with a very viscous gum
A lot of this has been covered, and more!!! Read the archive.
Judy