Liquin is an alkyd medium used in oil painting that is formulated to speed up the drying rate of oil paint. The fluid version (Liquin Original) increases flow and transparency of the paint it's mixed with, while the impasto version, stiffens the paint.
Liquin is a brand produced by Winsor & Newton (Safety Data Sheet). Other paint companies also produce alkyd mediums, for instance, the one produced by Gamlin is branded Galkyd.
Liquin a petroleum-based medium, and ought to be used in a well ventilated studio and the usual safety taken when using it e.g. being careful not to get it in your eyes, on your skin etc.
