Can You Add To Finished Sculptures After They Are Cured?

Yes. You can continue to add more layers of Pal Tiya Premium onto existing work for weeks and even months afterwards - with the right surface preparation. 

Any area you want to add to later must have a very rough surface, preferably with deep ridges and furrows. Scratching heavily with a fork while the mix is still soft will give you a good 'raked' surface. If the area is dry and fully cured, use a chisel or a hand grinder to create deep rough grooves in the surface first. When done, wet the area with water and pat mostly dry. 

While there is still a slight amount of water present, add the next new layer. Polymer bonding-agents have also been suggested, but we found in practice that Pal Tiya Premium bonds to itself well enough to survive our extreme weather-testing.