RE: Printing on Al - my experience
Rajul, thanks much! A victory for persistance that is - isn't it? We want (to see) samples, we want samples! ;) (Seeing other's work here always motivates and/or inspires me.) Jacek, IME gum will not hold/cling onto plain acrylic gesso (whatever brand and/or marketing ploy). You need to make it more toothy/porous by adding extra calcium carbonate and/or pumice powder and/or sand flour (as Rajul does) ect. I was able to print on Al with calcium carbonate added gesso; it worked well. BTW, I'm leaving the idea of gum on Al in favor of casein on Al since it seems to hold very well to acrylic gesso sized "paper" surface (I couldn't manage this with gum)... I'm in the middle of calibrating casein (a slow process since I'm in the Princes' Islands in Istanbul now and my actual home/lab is 12 nautical miles away!), as soon as I'm confident I will try it on wood and Al... Regards, Loris. -----Original Message----- From: Jacek Gonsalves [mailto:jacek@jagnight.com] Sent: Friday, July 10, 2009 8:04 AM To: alt-photo-process-l@usask.ca Subject: Re: Printing on Al - my experience Hi Rajul, Thanks very much for all the information! Though wouldn't just the ground of Acylic gesso give you the tooth it would need to apply coats of whatever alternative process your using? Btw what is your consistency,/mixture of your 30ml Gum Arabic to water? Cheers Jacek Quoting Rajul <eyeear@shaw.ca>: > I was able to get good prints on Al by the method I describe below. > Although I continue to fine-tune the procedure, the set of prints I > have are happy outcomes - flaws and all. I am thankful that gum arabic > served to increase the viscosity sufficiently to keep the sand flour > particles in suspension through the coating steps. > > 1. CLEANING PLATES: > Clean plates w soapy water (tear drop test for cleanliness). > Clean 3x w 99% isopropyl alcohol. > Mask borders if desired w painters' tape or tackier tape. > > 2. GROUND PREPARATION: > 30 ml of 14 Baume Gum Arabic > 60 ml water > Add acrylic gesso (I used Stevenson's) to desired opacity > 10 g Sieved Sand Flour > Pot. Dichromate powder equivalent to the concentration used to get > shadows to print > (I found 2% more than enough) > > 3. APPLICATION OF GROUND: > a. Use a dampened, squeezed out roller > b. Pour an aliquot of the stirred ground on to plate and apply it > uniformly w roller > IMPT: helps to have roller barely charged. Hold it in a > sandwich bag while c and > d (below) are carried out to prevent it from drying > c. dry coat w hair dryer set on hot > d. UV for 1 min to harden entire coat > e. Turn plate 90 degrees and repeat b-d till ground is of desired > thickness. > > 4. GELATIN SIZE: > 4% gelatin hardened w HCHO and containing ever clear is applied on > 3 consecutive days (allowing gelatin to dry for 24 hours between > each application). > > 5. APPLICATION OF GUM EMULSIONS: > - Use a 10% amm. dichromate stock for mixing w gum and water > color pigment > - It HELPS to dampen plate w a wetted, hand-wrung towel before > brushing on > emulsion with a dampened, flicked, foam brush to get streak-free spreads. > - dry coat w an overhead fan. > > - If, during development of an exposed gum layer bubbles form between the > ground and the Al surface, REJECT the print: the dried bubbles prevent > close contact between the negative and the printing surface during > subsequent > gum passes. Rate of bubble formation was 1 in 24 plates in my hands. > > 6. CYANO PASSES: > Can be done on top of gum. This requires long exposures (~1 hour in the > shade on a sunny summer day). > > - If there was any balling of the gelatin when the gum emulsion was applied > (resulting in raised dots that may be colored or white), the cyano > emulsion will clear them. In some prints, I found these dots to be > a windfall! > > > I hope the above persuades more gummists to take on Al. Questions or > comments are welcome. > > > Rajul
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