1From George Washington to James Jay, 12 May 1780 (Washington Papers)
GW is referring to invisible ink for espionage activities.
2From George Washington to James Jay, 9 April 1780 (Washington Papers)
GW sought a new supply of invisible ink for espionage activities (see
3From George Washington to Major Benjamin Tallmadge, 5 February 1780 (Washington Papers)
...last three words. “Stain” and “counterpart” refer to invisible ink and reagent.
4From George Washington to Major Benjamin Tallmadge, 30 October 1779 (Washington Papers)
GW is referring to the chemical reagent for invisible ink (see
5From George Washington to Major Benjamin Tallmadge, 24 September 1779 (Washington Papers)
...3.” The “stain” was a type of invisible ink. Woodhull, as Samuel Culper, probably enclosed...
6From George Washington to Major Benjamin Tallmadge, 25 July 1779 (Washington Papers)
For background on this invisible ink, and its initial use, see
7From George Washington to Major Benjamin Tallmadge, 13 June 1779 (Washington Papers)
GW is referring to invisible ink, which he sent in late July (see