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Keith,
The long delays in plate prep gave me time to attend to other must-do's. I persisted with Al in the hope that if I understood what was required, with persistence, I might be able to handle other surfaces. It proved to be a welcome change from the paper routines.
As with gelatin, gum arabic forms a colloid with dichromates. Since unexposed dichromated colloids get washed off during development, I thought exposing the KD- containing ground layers to UV might prevent this. This proved to be the case. I used KD because I had a larger supply of it than of AD.
Sand flour is something I picked up at Fusion Glassworks Inc., a small outlet located in an industrial district of Kelowna. They cater to the needs of artists who work with glass. Tel. 250 765 8806; TF 1 800 663 5071(I don't know what TF stands for). Their website: < www.fusionglass.com> and email: < sales@fusionglass.com>. They might be able to suggest where you could try to obtain it in your area. One packet of sand flour (1 kg?) was $6.95 Cdn.
Have fun with your Al stock! Rajul
On 9-Jul-09, at 4:51 PM, Keith Gerling wrote: Rajul,
I really appreciate your extensive research and the time it must have taken to get this all working. Personally, the reason that I used aluminum was to save time and money and your approach seems to take a whole lot of time. But I will try it, if for no other reason that I have a truckload of aluminum sitting here!
So what is "sand flour"? Where do you get it? Googling brings up all kinds of importers and nothing that looks like a mail-order or local source.
Thanks
Keith
On Thu, Jul 9, 2009 at 5:42 PM, Rajul <eyeear@shaw.ca> wrote: Importantly, after each coat of ground is applied and hot-air dried, it is UV'd for one minute. This prevents the ground from washing off (it did initially when I failed/forgot to UV the first few coats). The xs KD washes off during development of a gum pass.
I forgot to mention that the ground should be allowed to dry (I let it sit overnight) before applying the size.
Rajul On 9-Jul-09, at 2:28 PM, Keith Gerling wrote: This is fascinating. You include Potassium Dichromate in the ground?
On Thu, Jul 9, 2009 at 4:19 PM, Rajul <eyeear@shaw.ca> wrote: 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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