Lefranc Oil of Spike

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

From their website: Natural spike lavender oil is obtained by distilling lavender. It evaporates very slowly, making it ideal for producing very precise, transparent brush strokes. It is used to create preliminary sketches. Mixed with a medium, it activates the retarder effect.