"But Money, Wife, is the true Fuller's Earth for Reputations; there is not a Spot or a Stain but what it can take out. A rich Rogue now-a-days is fit Company for any Gentleman; and the World, my Dear, hath not such a Contempt for Roguery as you imagine."
–from The Beggar's Opera
by John Gay, 1728
I'd heard that line from the famous 18th c. ballad opera many times (yes, in true, shameless, NHG fashion, I like The Beggar's Opera the way my daughter likes High School Musical), but I hadn't really given much thought to what exactly fuller's earth might be.
Once again, the ladies in the milliner's shop of Colonial Williamsburg came to my enlightening rescue. That grey-green powder is fuller's earth, and a marvelous substance it is, too. It's a clay-like substance mined from the earth (you don't make it; you dig it), and in the past it was much used as an all-purpose dry-cleaning agent. It can lift out that greasy gravy spot on your lovely new waistcoat, and it can remove the mustiness from your woolen cloak after a summer in a wardrobe – which is why it was found in the shop of a mantua-maker or tailor.
It's called fuller's earth after fulling, an 18th c. trade that's mostly forgotten today. Fulling was one of the final steps in processing woolen cloth. A fuller rubbed a mixture of fuller's earth and water into the cloth to remove excess lanolin and other sheepish impurities that might remain, as well as fluffing and brushing the fabric's surface to finish it.
But I also learned that fuller's earth is still very much in use today. In demand as a "green" cleaning substance, it's also used by the military to help decontaminate uniforms affected in chemical warfare. It's an ingredient with many applications, from medicine and engineering to movie special effects. More humbly, it's used in kitty litter and dry shampoo.
And once again, what's old is new....