On Sat, 14 Sep 1996, Terry King wrote:
> 10% solution of gelatine at a temperature above 104 F, below this it will begin
> to gel which should contain the same amount of powder paint as gelatine and 5
> cc of glycerine for every 100 ml of solution thoroughly mixed together.
My info says it doesn't much matter what bloom gelatine you use -- I
assume you're using the Croda. 300 bloom?
Is "same amount of powder paint as gelatine" the same amount of
*powdered* gelatine? By weight or volume? Do you mix in liquid in a
blender or mix dry before adding water?
> This should be poured onto a dampened absorbent paper which has been squeegeed
> onto a flat level levelled surface with raised edges, about 5 mm. Remove any
Raised edges on the absorbent paper or on the flat levelled surface?
> ...The paper should be wall lining paper from the decorators merchant
> or if that is not obtainable in the land of the loo seat protector, try
> lintless blotting paper from the art print store.
How about heavy brown wrapping (parcel) paper? Or I have a big supply of
tough old bristol drawing paper, not thick but strong....
> Leave the gelatine to set for two or three hours and then cut the paper free and
> place in a cool dry place to dry slowly for a number of days depending on the
> ambient humidity. Here after a week there should be fine shiny surface of no
> apparent thickness.
Some sources advise drying in a "dust box" or cleaner-than-reality
environment....?
> Sensitise in a 3 % solution of am. dichromate at 55 F for three minutes. The
> tissue will go gooey at much above 60 F.
Klaus rolled a mix of half alcohol (isopropyl or rubbing alcohol), half 10%
dichromate with a sponge roller onto the pigment sheet in a room about 75
degrees F, then hung to dry. No problems that I could tell from the
ambient temperature (tho it's true that when one fell off the drying room
wall & a student stepped on it, it left big footprint).
> Expose under a negative with good gradation but very high contrast range, up to
> 2.8 will work.
I have, BTW, & I only mention this in passing, an old article says you
can print carbon on a "normal" negative provided you do something author
says, which I'll look up -- think it was *weak* potassium dichromate left
in tissue a day.....
> the carbon tissue to the receiving tissue and place another sheet of glass with
> two demijohns of water as weights for half an hour. There should be two sheets
> of lintless blotting paper one on either side of the two tissues before they are
> sandwiched betweeen the glass.
We used old newspapers instead of lintless blotting paper, perhaps not "the
best" but seemed OK, & needless to add, price is right.
Also, nothing so heavy as demijohns as weights -- just a sheet of plate
glass.
> The tissues should the be placed in water at above 104 F until beads of
> dissolving gelatine appear at all four edges.
That's exactly the word. We saw the "beads". Eureka!
> Reduce the temperature of the water to 60 F.
Instead of "reducing" temperature, we moved to a 2nd tray, saves water &
effort. And incidentally, tray one, a very deep one, got full of black
water, but still apparently stayed hot enough to be used for the whole
operation.
One student transferred her print to wrong side of receiving paper. Very
interesting effect...
Judy