Vallejo Pigment Binder 30 ml. is a colorless medium that is mixed with acrylic paints; it improves fluidity, increases transparency and slows the drying time. Pigment Binder is good for applying shadows, glazes and processing pigments.
Vallejo Pigment Binder was previously Vallejo Glaze Medium, the product has only been given a different label.
For a detailed explanation about Pigment Binder / Glaze Medium check out the YoungWolf7's Lair blog