Winsor & Newton Watercolour Medium has the same properties as Gum Arabic, but also increases the wetting of the paper. This will improve the flow of washes across the paper.
Winsor & Newton Watercolour Medium is usually mixed into the watercolour wash, but can be added to the jar of water if you prefer to use it throughout the painting. This medium should not be used with acid sensitive colours, namely those containing Ultramarine.
Winsor & Newton Watercolour Medium in 75ml bottle.