In 1773 Gainsborough wrote to his friend William Jackson, giving him details of a new technique he had developed. After constructing the main outlines of a drawing he recommended using '...Bristol made white lead which you buy in lumps at any house painters; saw it the size you want for your white chalk; the Bristol is harder and more the temper of chalk than the London.' Having achieved the desired effect the drawing was dipped '...all over in skim'd milk...' in order to fix the lead white. Further washes were then added and the drawing sized with a sheet of gum arabic. The sheet would then be varnished '...three times with spirit varnish'.