The Daler-Rowney Watercolour Mediums Ox Gall Solution is a professional-grade wetting agent engineered to significantly improve the flow and blending capabilities of your watercolour paints. By reducing the natural surface tension of water, a few drops of this concentrated liquid allow heavy or stubborn pigments to disperse smoothly across the paper for flawless, streak-free washes. It acts as an excellent levelling agent on hard-sized or resistant papers, expanding your working time for intricate wet-on-wet techniques and soft atmospheric effects.