Art Spectrum® Oil painting mediums are based on sound painting principles. Today’s advanced testing indicates that the use of turpentine alone as a dilutent for oil paints is to be avoided, as it is too easy to destroy the binder and benefits of carefully milled paint. Sound painting principles involve painting from ‘lean’ mixtures to ‘fat’ mixtures of paint – essential when paintings are completed over a period of time. This ‘fat over lean’ technique prevents cracking in the paint film during drying.