Looking at the results here maybe this rosin process needs long exposure times to harden the mix, given it only takes a minute or so to develop in kero fumes, might try a 3 hour exposure, as i have only been useing 1.25 hours as i was worried about over exposure.
Any more progress heather ?
Since I am not currently involved in attempting physautotype, I hadn't posted, but I think you are on the right track. I have experimented with the heliograph process, and found that it exposes from the top of the emulsion down, meaning if when my exposure was insufficient, the image would begin to show as I developed, but would then wash away as development continued. This isn't the same process, but I feel perhaps the same effect applies.
I think that this process is not unlike many of the old processes that require negatives with considerably higher contrast than do silver gelatin prints. Since it is a positive process one
needs a lot of density in the "shadow" areas to alow for enough exposure of the highlight areas and not over expose the shadow areas. I find "paper positives" as opposed to film or transparency possitives to be very suited to this process. For negative processes I almost always use Pyro or Pyro-Cat development of film.
For experemental purposes I use Ink Jet Velum as regular plain paper is too dense for Physautotypes.