"A plant, by the Americans called anil." Samuel Johnson, A Dictionary of the English Language: . . . in 2 vols (London: Printed by W. Strahan . . . 1755; facsimile reprint by Longman Group UK Limited, Harlow, UK, 1990), n.p.
". . .indigo grows in the East Indies. The blue dye given to cloth by this plant is preferable to any other; because it is of so fixed and desirable a nature, that it is not affected either by acid or alkaline substances." Encyclopaedia Britannica: . . . in 3 vols (Wsinburgh: Printed for A. Bell and C. Macfarquhar. . .1771; facsimile reprint by Encyclopaedia Britannica, Inc., Chicago, 1979), Vol. I, p. 634.
Indigo plants pulled, fermented, dried; to use, powdered, re-fermented in chamber lye (stale human urine), and used. Because the cholor is the result of a chemical process, oxidation, that occurs when the cloth dipped in the dye is exposed to the air, the color is permanent and will not fade when exposed to light or washing. The process is complex and time-consuming.
Indigo was available in "the world of William Penn." Benjamin Hawley, a Chester County farmer, recorded purchasing it:
22 May 1770 - 22 oz for 2s 4d (p. 19)
14 Dec 1771 - 1s2d (p. 57)
1 June 1772 - 2 oz 2s (p. 68)
2 Mar 1773 - 7d (p. 85)
17 June 1773 - -- (p. 90)
23 Mar 1776 - 1s2d (p. 141)
Only one reference to dyeing:
29 July 1789 - "Lydia dying her yarn . . ." (p. 220)
"Diary of Benjamin Hawley, Chester County, PA 1769-1782," (Unpublished manuscript/typescript in the Chester County Historical Society, West Chester, PA).
There were other uses for indigo:
"75. To make Plain or Painted Waffers.
. . .If you painnt them paint before the/y/ are Baked scuth in eele [cochineal, color not given, but it would have been pink or red] for Yellow Saffron for green with Indigoe what fanceys you please. . ." ["Receipts"] (Unpublished, undated manuscript in collection at Stenton, Germantown, Philadelphia), p. 32. Comment:
Blue as a food coloring in 17th- and 18th-century dishes was usually made using violet syrup which is navy blue unless it has been turned purple by adding lemon juice.
"A Cure for a horse that has the belly Ake take a Quarter of an Ounce of Indego a little hard Soap a pint of Strong beer & pound the Indego fine and shave the Sope fine then mix it together." "Peter Dicks his Book 1715" (Unpubished manuscript in The Delaware County Historical Society, Chester, PA), p. 195. Comment: This collection includes material in many different handwritings, from 18th-, 19th-, and 20th-century recorders. The above receipt does not appear to be in Peter Dick's handwriting.
So, why was Benjamin Hawley purchasing small quantities of indigo?