To use our knife technique we require highly viscous paints. Oil colors that are the consistency of jam are formulated to spread easily with a brush, but they either slide off the knife or form drooping strings that make precise control impossible. A thick and granular consistency is ideal for knife painting, but this consistency should not be achieved by the addition of fillers, which dull the colors. Dense pigments are more expensive but well worth it because they enhance viscosity without dulling the color. Several manufacturers make oil colors of a suitable consistency, but strangely no one manufacturer makes colors that are all free of what we call “stringiness”.
Daler-Rowney Artists Oil Colours, Winsor and Newton and Old Holland are particularly suitable in consistency for knife painting, but there are odd exceptions. For example Old Holland earth colors are the perfect consistency for knife painting but their Titanium White is stringy. We use Winton Titanium White oil color.
Readers who know their oil colors will recognize that Winton is the brand name for Winsor & Newton’s oil colors for students. This color is the single exception we make to the rule that we always use “artist” quality oil colors rather than “student” quality. The reason that we use Winton Titanium White is simply that it has the very best consistency for knife painting of any white we have ever encountered. Is there a downside? No. There might be a downside if we were comparing Cadmium Yellow (artists’ quality) with Cadmium Yellow Hue (students’ quality) because manufacturers substitute less expensive pigments in the students’ oil colors for their more expensive counterparts in their “artists” or “professional” lines. The students’ colors are sometimes not as brilliant or durable as the artists’ colors. But Titanium is Titanium. If it might be a little less opaque than the artists’ pigments the difference would never be noticed in the thick applications that we knife painters use. Someone who paints with thin washes may be able to detect the difference. Meanwhile, for knife painting, it’s gorgeous.