Is turpenoid better than turpentine as an oil painting medium?”
Turpenoid, which is Grumtine, which is really Gamsol, all of which honestly are nothing more than regular hardware store odorless mineral spirits are 1) a rip off, 2) petroleum products (a form of K2 kerosene) are less active than water. No kidding, a few drops of water in most oil/resin mediums will do more to improve it than any amount of OMS (odorless mineral spirit). Here’s why: all that it does is evaporate. It does not enter into any of the oxidizing reactions needed for paint to dry, whereas water does enter into reaction. It’s also a gentle solvent. That said, OMS can be of advantage to anyone wanting a medium that dries slowly and can be applied in thin layers. Turpentine draws oxygen from the air and brings it into reaction with the oil in the paint. It’s a more agressive solvent. Now here’s the tricky part, turpentine is what’s called a non-polar solvent and OMS is a polar solvent. That means that they are on opposite sides of the electrical fence. When they combine they mee
