U of S | Mailing List Archive | alt-photo-process-l | Re: resinotype question

Re: resinotype question



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 30C."  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 50C, 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