You wrote:
>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?
Yes because we bought a cwt of it last term, but when I first made tissue I used
leaf gelatine from the delicatessen which is a lot softer. As you say there is
not much difference but a test would be worthwhile.
>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?
I meant the same weight but this was only a rough guide: it is true of the
powder paint from the Early Learning shop but pure pigment might need much less.
I stir the powder in while the gelatine is in the water bath using a plastic
photographic stirrer but I think that one would need to be used to cooking to do
this. A good wire whisk would probably be better.
>> 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 surface. I have a piece of acrylic 5mm thick where the outside inch has been
cut off and stuck back onto thesurface at the edges.
>> ...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....
I think that it would be worth giving both a try. The material needs to have
wet strength and be absorbent and flexible so it can be peeled off. This is
another worthwhile field for tests.
>> 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....?
I put mine in the dark box I use to dry my sensitised papers.
>> 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).
I am not saying Klaus is not right but although rubbing alcohol ( surgical
spirit in UK speak ) in the sensitiser will give quicker drying times, as a
personal preference I avoid spirits in confined spaces (one gin and he's
anybody's). The surface is also less delicate at the lower temperature.
>> 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.....
I should have said:
'Expose under a negative; the process is capable of printing from negatives
with a very wide density range even up to a max of 2.8'.
>> 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.
I use old newspaper too. I think weighting the sanwich down will give more
consistent results.
>> 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!
At this stage I engender calm in the group. A few 'oms' never did anyone any
harm !
>> 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.
But changing the water while you are developing gives a good guide to when it is
done.
>One student transferred her print to wrong side of receiving paper. Very
>interesting effect...
Once I had three in a row try to develop it without the receiving surface. I got
down on my knees and prayed but that was during a gravure class.
Terry