All,
A few weeks ago there was some discussion on PVA sizing and I decided to try it for gum. I also bought some rabbit skin glue, but have not gotten to it yet. Anyways, the PVA is Gamblin PVA size in 32oz bottle. Here is what I have done: soaked a few sheets of Fabriano Artistico paper in room temperature water for about 30 minutes re-shink and then dried them. Next, brushed PVA/water mixtures at about 20cc/sheet of paper (these are big sheets 22x30). Started with straight PVA and went on diluting it 1:1, 1:2 and 1:3. Brushing is quite easy. After drying the papers overnight I printed some test strips. Straight PVA and 1:1 dilution left the paper too slick and the gum would just flake off. The 1:2 turned out to be a miracle! The gum coats the paper nicely and after a few brushstrokes it seems to cling to the paper. Rolling with a foam roller to smooth it out was so easy. My impression is that some of that PVA size is redissolved and mixed with gum when coating, but that might not be the case. At 1:3 dilution there might be some staining after development, but it might clear with a longer development and I just did not have to to mess with it aftr I saw the results of sizing with 1:2 dilution.
Here are some examples of test prints done on that paper. I was aiming at refining my one coat, one exposure of very long range gums, and I think I finally have arrived at final solution. PVA sized paper clears beautifully leaving no stain behind. Long exposures and blech develoment result in full tonal range with absolutely no stain on the paper. I have also included a test strip with a shorter exposure and very long development. I do not have patience to develop for 8 hours or more, but it resulted in very nice tonal gradation and no stain. Actually it is not even possible with 6-12 prints that I handle at a time to develop that long, no room to soak it all. Bleach development takes at most 30 minutes.
Here are the test strips
http://picasaweb.google.com/marekmatusz1/GumAndPvaSize#
Marek
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