Re: resinotype question

[Keith Gerling <keith.gerling@gmail.com>]

Thanks you very much for your quick reply.  I guess I had the pigment to rosin proportion reversed!  Do you happen to know which pigments might not be compatible with this process?

Keith

www.gumphoto.com

On 10/30/07, Alberto Novo <alt_list@albertonovo.it> wrote:

Keith,
> OK, so I've melted up two teaspoons of dry pigment (raw umber, burnt umber,
> and ivory black) with a teaspoon of violin bow rosin over a gas burner and
> have reduced the resultant mass to a pile of powder by grinding it on a
> piece of sandpaper.  It looks to me a mixture of very fine to rather
> not-so-fine particles.
The ratio pigment/rosin looks too high. Though with some pigments I need to
rise it (and raw umber is one among those), I achieve the best results with
a mixture 4/10 w/w pigment/rosin.

> Regarding the gelatin:  Your notes say "The gelatine must not melt, once
> swelled in water, below 30°C."  The gelatin is simply swelled in warm water
> and coated on the paper?    I've never worked with un-hardened gelatin, so I
> have no real experience with this, but I'm skeptical as to how this gelatin
> coating will withstand a rather lengthy wash.  Am I missing something, or is
> it really this easy?

You need to coat the paper with a warm solution of gelatine, say at 50°C, up
to 35-50 g/m2 as dry weight. This can be easily achieved if you put your
pre-wetted paper over a glass leveled with a spirit-level, wipe off the
excess of water with a towel or a chamois, and then spread  over (with the
back of a spoon, your finger, a comb, etc.) the measured amount of warm
gelatine solution.
Did you never made oilprints? The preparation of the paper is more or less
the same.
My note about the minimum temperature is because you will need, just before
powdering, swell the paper a few degrees below the melting point. The
gelatine must become a little tacky. If the melting point (not really a
point but rather a narrow range) of the gelatine is too low it will not hold
out against the long soak required to wash out the dichromate, especially in
the warm season.

Alberto