Sizing - Gum Bichromate Prints
I am about to take the plunge and try my first gum prints. I know that this will be a long process, I plan to take notes on the differing steps and I am prepared (I think) for the inevitable ups and downs of the process itself.
I plan to start sizing the paper in the coming days but would welcome some advice on sizing techniques. Has anyone used a coat or coats of PVA glue rather than the usual three coats of gelatin? I don't mind using the gelatin (although I hear that there really is a need to harden the gelatin with alum to get the best results which I don't have at the moment). I have, though, read online that you can use PVA diluted 1:2 with water (after preshrinking) and that the gum/pigment/bichromate sensitizer takes well to this base. There is also apparently no pigment staining and the surface is not so shiny (as with gelatin).
Has anyone had any experiences with this sizing? I have used gelatin for sizing in other processes which I am happy to do with the gum prints (although I do find gelatin sizing a bit of a chore if I have to be honest). I may try both, of course, but thought I would take some advice from those who have trodden the path well before me.
Thanks for considering this.
I use Gamblin PVA for my sizing. I mix it 1:2 and use a couple of coats. Some people use it straight, but that does not work for me. I guess the humidity in Texas keeps it tacky when used straight.
Some people report mixed results with the PVA. For me it works great. When mixed 1:2, you cannot even tell it has been applied, once it dries.
I used to use gelatin with formalin as a hardener. That works great, but formalin is quite nasty. PVA is so much easier.
I use Gamblin PVA size for sizing paper for gum printing, too. I use it full strength (had problems at 1/2 strength with pigment staining of the paper).
I apply it with a dry foam brush dipped into a glassware container. Then I hit it with a hair dryer on medium cool (that's the only setting that works on my hair dryer) and when it starts to get tacky I smooth the coating out with a clean, high density foam roller.
Here's a gum over palladium print with 2 gum layers using the Gamblin PVA size.
edit: I don't know where you got the 3 coats of gelatin. I only ever used one coat of gelatin hardened with formalin, but had to look for other sizing options because of my new workspace and a decided lack of ventilation. Now you'd have to pay me to switch back. With the formalin/gelatin size I basically saved up a bunch of palladium prints to size all at one time and then start printing the next day, but with the Gamblin PVA I just size as I go because it's a 20 minute process from dry-to-dry.
Let's see what I've got in the magic trash can for Mateo!
Many thanks for the quick response, I think that I will give the PVA a try. As the main purpose of the size is surely to keep the sensitizer from soaking too much into the paper I couldn't really see why PVA would not do just as well as gelatin and the print above is great.
Jeremy - I think that one (or maybe a couple) of the books I use on alt processes say that two or three coats of gelatin work best. Maybe it's a bit much, I'm not sure.
Will let you know how it goes and hopefully I will get some good results.
A couple of thoughts:
I agree with Jeremy, I don't know about three coats of gelatin. I'd start with one, and if that's not sufficient, then move up to two. But of course it also depends on how much gelatin you're using. I use 7 g in 200 ml water, in other words 3.5%, and one coat of that, hardened with glyoxal, works fine for me. The issue here is tooth, the name for the fibers in the paper that the hardened gum needs to hang onto in order to not float off into the water. If the tooth is clogged up with gelatin, then the gum won't have anything to hang onto, and it will slide off. So you want just enough gelatin to keep the pigment (not sensitizer; the sensitizer easily flushes out of the paper in development) from sinking into the paper as stain, but not so much that you clog up the tooth.
This is also an issue with the PVA size: you want the size to be thin enough to sink into the paper and protect it, not so watery that it doesn't protect the paper enough, not so thick that it sits on top of the paper and clogs up the tooth. Which dilution works best for you will depend on your paper; as you can see above, different strengths work for different people. So you might have to do some trial and error before you hit on the right combination for your paper. Good luck,
P.S. Jeremy, I'm glad the PVA Size has solved your problem. Looks great!
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Thanks Katharine for the great advice. I will start today with PVA and see how it goes. I will give it a go on full strength as well as the 1:2 dilution and take it from there. Appreciate your help.
I just got to ask, curious minds want to know: is there less risk of shrinking when you use gelatin and hardener, compared to using PVA?
“Do your work, then step back. The only path to serenity.” - Lao Tzu
How much PVA size [total solution needed to fully coat, whatever the dilution] is needed for a 22x30 sheet of paper, FAEW for example?
How do you mix up the glyoxal to use as hardener? I've seen directions to use it in the same proportion to use as the formalin, but the glyoxal comes as a powder, not as a liquid, so how do you mix it to get it to the same strength?
Colin...I've never sized a full sheet with PVA size, however based on my experiences sizing small 4x5 and 6x7 pieces of FAEW, total solution in any dilution should be around 12-15ml roughly. I just mix it into dilution 1:1 or 1:2 and bottle any leftovers. I dip the brush into the solution to use...
I'm sure Steve can answer with more accuracy...