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Re: bubbles in gelatin

Folks:

Kremer Pigments makes a defoaming agent which is very helpful in suppressing
bubbles in gelatine emulsions.  Only a few drops per 500 ml. batch are needed.

Joe Arkins
Long Island City, NY

Judy Seigel wrote:

> On Tue, 10 Oct 2000, Sandy King wrote:
>
> > I size paper for carbon by brushing on a 2-3% gelatin solution (with
> > glyoxal added) with a foam rubber brush about 3 inches in width.
> > First I soak the paper, then place it on a flat surface and squeegee
> > it out. Then, I blot the face with a clean towel to get off all of
> > the excess water. To coat I use about 100ml of the gelatin solution
> > per sheet of watercolor paper, 22x30" size. When the gelatin sets you
> > can dry it on a rack or hang to dry, as you prefer. I often use
> > alcohol to get rid of the bubbles, but more than you, as much as 8
> > ounces per liter of solution.
> >
> > This method is much less messy than either of the methods you
> > describe. In fact, there is virtually no mess at all.
>
> What do you "squeegee out" with?  On what paper?  It doesn't rough up the
> surface? My squeegeeing has not (yet) been satisfactory.
>
> Meanwhile, I haven't tested it as well as I meant to -- tests left
> midstream last May need to be started again -- but my experience so far is
> that gelatin brushed onto the top doesn't give as good a size for
> multiple-coat gum as when paper is immersed in the gelatin, which
> permeates it more throroughly. For carbon, I gather you only do one
> transfer, but a gum print can have 5 or 6 or more coats -- sometimes with
> long soak times. After a couple it usually needs resizing, but gelatin put
> ON TOP OF existing color is usually (IME) yucky, makes it look hazy and/or
> greasy. I also suspect that another gelatining & hardening will shrink the
> paper more if anything can & give more register problems.
>
> Also, I find, not all, but many papers will curl if coated only on one
> side.
>
> I'm curious about the glyoxal in the gelatin, however -- that was also in
> the unfinished test series -- glyoxal *in* the gelatin vs.separate coat. I
> got down to those unfinished tests in the alleuvial layer in studio a few
> days ago & found, to my *astonishment,* that the test labelled "glyoxal in
> gelatin" was discolored, the edges where there was a build-up of gelatin
> somewhat carelessly applied apparently, not visible at the time, but now
> VERY discolored.  The "glyoxal separate coat" sheet showed no discoloring.
>
> I soaked the discolored piece in water 24 hours... some lightening in
> part of it but most stayed the same. That was Photographer's Formularly
> gelatin (basic subject of the tests) -- would all have same reaction?  On
> every paper? Who can say?
>
> As Mae West explained, so many tests, so little time... All things
> considered, I see no way to avoid the gelatin soak (& the 3 litres of
> gelatin I mixed last night were NOT enough) but would sure like better
> anti-bubble aid than alcohol.  I think there's one out there...
>
> Judy