From Francis Hopkinson
Philada. 30. May. 
Mr. Wright has made a most excellent Copy of the Generals Head; he is much pleased with it himself, and I think it rather more like than the Original. In Order to admit of it’s being pack’d up at all he has been oblig’d to expose it all this Day in the Sun. The Consequence is that the Colours will sink in, as the Painters call it, that is, it will look dead and without Brilliancy or Gloss. This is the Case with all Pictures. All the Colours are brought out again by a Varnish. This Operation must be performed in France, as it can not be done till the Picture is thoroughly dry, for which you know there was not Time in the present Case. This Picture, being pack’d up in a close Box before the Colours are fixed, will cause those parts wherein white has been used to turn very yellow. To remedy this, it will be very proper to open the Box at Boston and unroll the Canvas so that it may have the Benefit of the fresh Air as long as may be, till you embark. If, notwithstanding this, you should find it has turn’d yellow when you get to France, you must stre[tch] it on it’s straining Frame, and expose it to the Sun, wetting it every now and then with a Spunge dipt in clear Water. This must be done for a Day at least until it is sufficiently blanched. But you must not carry the Operation too far. If you do the other Colours will fly off, and the Picture will loose all it’s Warmth and Force. Sir Joshua Reynolds blanches all his Pictures in this Way, and some Times over does it.
Remember me kindly to Miss Jefferson, wishing you both a pleasant and speedy Passage over the great Water, I am Your ever faithful & affectionate Friend,
RC (DLC). An entry in TJ’s Account Book for 28 May 1784 reads: “left with F. Hopkinson for [Joseph] Wright for drawing Go. Washington £17.10.”
See illustration in this volume of the portrait of Washington by Joseph Wright.