Hi Sandra, Is there a reason why you want to do this with clay? For
over 30 years years now I've been using either a dental impression
material called Aquasil, or Castaldo's Quick-Sil, or one similar to
Quick-Sil that I got from an audiologist. All three self-cure, the
Aquasil taking about a 15 minutes at 70F (surface temperature) and
although the container on Quick-Sil says 15 minutes I find it takes
closer to 30. In the Arctic two summers ago it took overnight!
It's not easy to warm a rock surface to 70F in the Arctic, or on the
coast of Newfoundland for that matter!
All products involve mixing two parts together. Aquasil is about
the consistency of toothpaste and gives the most detailed
impression. It's also messier to use. The other two are putty-like
and easiest to use in the field. Both give very good results.
Colleen Chamcook, NB