P.S. Anyone have experience with Elasticlay? I'm wondering whether
that also has plasticizers that don't full disappear and may interact
with everyday material, e.g., furniture finishes.

Hi Irwin!
Thanks for the info on the eraser clay. I think you are spot-on about the
plasticisers.

I have Elasticlay from over the last twelve years' use, (and I may have this
result because of the last eight spent in high altitude and low humidity--) all
my elasticlay molds are VERY dry, very hard, and many have fine cracks. Many
also have a bubbly sort of "bloom" on the surface, a roughened texture that was
NOT there originally. All were baked according to directions, all were OK
(flexible) at first.Many were used heavily, some not at all, all show this
dried-out quality; so I don't think its because of reactions with raw clays.
And all are VERY hard. I have switched to using Miracle Mold RTV for casting
molds.
Sarajane

Sarajane's Polymer Clay Gallery
http://www.polyclay.com