Re: Printing on Al - my experience
Jacek,
I tried many combos of acrylic gesso plus additives (CaCO3, granite
dust, then sand flour) and realized that to keep any of these in
suspension, the viscosity of the mix had to be increased. This was
done by adding gum arabic as detailed in the recipe I communicated
earlier. The gesso alone does not provide enough tooth for repeat gum
passes.
Could you please re-word the question you have re. the consistency of
the gum:water mix?
Rajul
On 9-Jul-09, at 10:04 PM, Jacek Gonsalves wrote:
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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