Gamblin Art Sketching oils are made for painters who are learning new techniques or experimenting with new ideas. First formulated over 500 years ago, "sketching paints" allowed the masters to work our their ideas and to make practice paints for their apprentices. Gamblin Art Sketching oils are made from approximately half the colored pigments of artist grade oil colors; extenders that have good film forming properties are added to Gamblin Artist's oil colors. Each extender is paired with the pigment so that opaque colors remain reasonably opaque and transparent colors are not clouded. Gamblin Artist's oils and Art Sketching oils can be used on the same palette; when painters are ready they can gradually add more Gamblin Artist's grade oil colors without having to learn how the Artist's colors work all over again.