By adopting the procedure for grounding the plates (detailed in the earlier post today), I seem to have overcome the problem of water bubbles between the metal and the gesso.
My interpretation of the recommendation to replace water with gum arabic or water glass is that either would increase the viscosity of the mix which would make for a more uniform dispersal of the sand flour and (hopefully) prevent it from agglutinating and forming the pock marks on drying the developed print.
If that is indeed the case, the next step will be to determine the extent to which water should be substituted. A highly viscous mix would make its even spread difficult, something we run into when spreading a gum emulsion to print shadows.
It took me a whole morning of phone calls to identify one local source for water glass ($20 for 500 ml). If gum arabic is cheaper and eliminates pock formation, it might be one less variable to contend with and should be more compatible with gum printing.
Once again, ideas/suggestions are welcome.
On 23-Jun-09, at 7:16 PM, Keith Gerling wrote:
That sounds like an interesting approach. I see no mention of water bubbles between the metal and the gesso, and this is a problem that I often experience. I'm a little confused about the notion of substituting gum arabic or water glass for water. They are suggesting you dilute your acrylic gesso with gum arabic? Or water glass? Wouldn't this leach out in the development? (or selectively hardened in the case of the gum?)
Please do keep us posted as this process takes shape.
On Tue, Jun 23, 2009 at 7:53 PM, Rajul <firstname.lastname@example.org>
I have made some prints on Al and am turning to the experts on this list for a problem I need to resolve.
The prints are impressionistic, and noticeably different from those on paper. They are sufficiently interesting to warrant refinement.
The ground is an acrylic gesso diluted with water to the desired thickness. To 250 ml of it are added 2 heaping spoons of flour sand (that has been sieved through nylon hose). This mix is once again sieved through the same material before applying to thoroughly cleaned Al plates with a roller. Each application is dried with a hair dryer on hot setting, turned 90 degrees and recoated. This is repeated 2-3 times till a desired opacity is obtained. Grounded plates are dried for 24 hours before application of formalin-hardened gelatin on 3 successive days.
Prepared plates are dampened with a wet towel before application of the gum emulsion. The sensitizer stock solution is 10% Am. Di.
The problem: upon application of the emulsion with a dampened foam brush, the surface sometimes develops holes in the gelatin layer. Notwithstanding, I continue printing 2-3 gum passes, sometimes run a cyano pass and everything seems ok. When I dry the developed print (hot hair dryer), I find pock marks that are either colored or white, suggesting that the flour sand has balled up. In some prints, this actually enhances the interest in the print. In others, it looks like a flaw that should be avoided.
The people who supplied me with the sand flour suggest that I use water glass (sodium silicate) or gum arabic instead of water in preparing the gesso ground before adding the sand flour to it.
Your suggestions would be greatly appreciated.