In 1999 I collaborated with various artists who painted the Hydrocal (aka plaster) castings I was making.  It took them less time to paint a sculpture then it took me to make the originals, reproduction molds and final sculptures. Although they turned out very nice, my decision was that these were no longer sculptures but paintings on plaster.. People “liked” them but they couldn’t be sold in a gallery and were worth less than the metal and ceramic sculptures I was making. I stopped letting anyone paint them. I went on to develop other methods and designed equipment to make glass sculptures.  Since then there have been a few people that copied the idea. Including a lot more that do body painting and painting on mannequins. IIt can be a nice effect but unless the artist is already well known, the paintings are worth less than then the sculptures.