Is blending medium water-based?

Yes, blending medium is water-based.  It is also slows drying and maximises the working time of your watercolours, allowing you to achieve smoother blends. Use the Blending Medium to work different colours into each other or to show a single colour in all its intensity levels. Ensures pigments remain on the surface and strengthens their bond. It does not affect the colour or its other properties and for maximum effect dilute with the medium only, but can also be mixed with water.
Extends working time even in hot climates.