U of S | Mailing List Archive | alt-photo-process-l | Re: Printing on Aluminum plates

Re: Printing on Aluminum plates

Damiano and Loris, many thanks for your suggestions.

At this point, it is a guessing game. The choice of an additive that will increase the viscosity of the gesso to keep the sand flour in suspension will depend on its availability, price and ultimately, the behavior of the additive. The ones to test and compare are gum arabic, casein and water glass. I will inform you of the outcome.

Wish you success in your various endeavors! Rajul

On 23-Jun-09, at 10:49 PM, Loris Medici wrote:

Hi Rajul, thanks for the update.

To me sodium silicate sounds more plausible than gum arabic. As Keith
pointed out, unexposed gum will dissolve. Sodium silicate is a highly porous
material (when dry!) which is used as a glue. I put printing gum on Al
aside, since I'm more concentrated on learning casein right now; it seems
that casein is better for hard to print on surfaces like Aluminum. (Hint:
it's used in leather paints...) It's much more robust and sticky compared to
gum arabic. An example: I never managed to do a nice gum print on surfaces
sized with pure acrylic gesso (w/o adulterants), but casein likes it a lot!
I dropped using gelatin sizing for casein prints; acrylic gesso sized paper
is much much better; whites are better preserved - much less or no staining,
gelatin sized paper stains (or darkens if you like) considerably with
casein, and sizing is much easier, no hot bath, no formalin, dries faster...
Also, with aluminum, you risk more flaking/cracking with each layer. Since
casein is able to hold much more pigment compared to gum, it will give you
convincing blacks / darkness in less layers eliminating the risk.

BTW, I purchased my technical grade sodium silicate for USD 1,5 per 1000ml!

All for now. When I'm confident about casein, will start to print on marine
grade plywood. There are 25 pieces waiting me to be exploited! ;)

Thanks again,


From: Rajul [mailto:eyeear@shaw.ca]
Sent: Wednesday, June 24, 2009 7:23 AM
To: alt-photo-process-l@usask.ca
Subject: Re: Printing on Aluminum plates

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 <eyeear@shaw.ca> wrote:

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

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.

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

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.