Royal Talens : Cobra Water Mixable Oil : Glazing Medium : 250ml

Composition: Vegetable oils, synthetic resins and water. 

Purpose: Increasing the flow and/or transparency, makes the paint fatter.

Qualities:
• Makes the brush stroke run slightly 
• Increases the gloss and transparency 
• No influence on drying time of the paint
• Increases the durability of the paint film
• Can be thinned with water
•Yellows slightly

A great video from Cobra that explains the different uses for the three painting mediums and how they can help you maintain the 'fat-over-lean' principle:

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