As the term impasto suggests, Liquin Impasto medium (previously called Oleopasto) from Winsor & Newton is a medium for thickening up oil paint to give more texture and body. Brush marks don't flatten or level out, but remain crisp and sharp.
Liquin is Winsor & Newton's brand of alkyd mediums, formulated to be quick drying. Liquin Impasto dries to a semi-gloss finish and, when dry, can be varnished as you would any oil painting. Quite how quick drying it is obviously depends on how thickly you apply it. But working with it, you'll get a feel for it.
If you wanted to build up very thick layers, build it up gradually, allowing each to dry otherwise the top layer might dry before the lowest, and then crack. For extreme texture, it'd be faster to do it with acrylic texture paste, before you started painting with oils.
The medium looks a little "cloudy", like it has a color, when it's by itself, but mixed with a paint it becomes "clear". My sensitivity to color, such as it is, didn't perceive any impact on the color, or color shift. In the photos here, I've mixed it with Rose Madder Genuine, a transparent color. (Check this larger photo and you'll see the medium by itself, and mixed with the paint, better.)
As you'd expect, the medium is very stiff when squeezed from the tube, coming out like a worm. But put a stiff-haired brush to it and it spreads readily, right down to a thin glaze. Mixing it into a paint color with a palette knife doesn't take long at all. Then the fun can start: painting with strong brushmarks which are retained. Given his love of paint texture, I bet Vincent van Gogh would've been thrilled with it!
• Stiffens oil paint, allowing you to paint with strong brushmarks remaining visible.
• There's a warning on the tube about allergic reactions as it contains butanone-oxime and cobalt carbonxylate. Use in a well-ventilated studio.
Disclosure: A review sample was provided by the manufacturer. For more information, see our Ethics Policy.