Wayde Allen (wallen@boulder.nist.gov)
Wed, 21 Apr 1999 09:55:11 -0600 (MDT)
On Tue, 20 Apr 1999, Mac Legrandi wrote:
> 1. Can I get good results with Knox gelatine? I bought 3 boxes today.
Yes
> 2. The info I found uses black Rotring drawing ink. Would the other
> Koh-i-nor colored inks work as well?
Don't know for sure. One concern is whether the inks are designed to be
water resistant when dry. Evidently they achieve this by adding a lacquer
or shellac (don't remember which) to the wet ink. In one of my tests this
apparently separated from the ink/gelatin mixture and floated to the top
of the tissue. The resulting tissue printed with a swirl pattern caused
by this film.
> 3. I will use the plexiglass method, but how thick should the emulsion be?
Thick enough that you don't print through to the temporary support. I
usually coat the tissue somewhere between 1 to 2 mm thick, or about the
thickness of a piece of mat board. The emulsion will shrink quite a bit
when it dries, leaving the dry thickness on the order of tenths of a
millimeter.
Are you planning to use the Plexiglas for coating the tissue, or as an
intermediate support in a double transfer? I don't think I'd suggest you
start out with a double transfer, but that is just my opinion. I'm still
fiddling with the single transfer process, and adding a second transfer
step looks to me like just another place for something to go wrong.
> 4. Can the sensitizer be brushed on rather than tray soaked?
So I've read. I've never tried that.
> 5. After exposure, I'm a bit unclear how you transfer the gelatine to
> paper. I understand the paper must be sized with gelatine first.
Float the tissue and the final support paper together in cold water,
remove them from the water and place on a smooth hard surface (glass or
Plexiglas works well) and squeegee them together working from the center
to the edges. They will probably slip a bit at first, but that shouldn't
be a problem. I then press the sandwich under some blotting paper and a
convenient weight for about 10 minutes. The next step is to develop the
sandwich in hot water (100 - 110 degrees Fahrenheit). The temporary
support paper is peeled off after the gelatin has softened (2- 5 minutes).
- Wayde
(wallen@boulder.nist.gov)
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