Lefranc Harlem Duroziez Drying Medium

Lefranc Bourgeois are a paint manufacturer with a long history of supplying to artists since their beginnings in 1720.

From their website: The Harlem Duroziez drying medium increases the brilliance and transparency of glazes. It enables the build-up of layers over the course of half a day thanks to the rapid drying effect of thin layers. It is completely dry within three days.