To get back to the original post [Ducks to avoid flying sugar/molasses covered "biscuits"]..

As far as I know, "It'll all come out in the wash" comes from Kipling's "Stellenbosch"

"..And it all goes into the laundry,
But it never comes out in the wash,
'Ow we're sugared about by the old men
('Eavy sterned amateur old men!)
That 'amper an' 'inder an' scold men
For fear o' Stellenbosh!..."

Stellenbosch (a south African town) was a posting for an officer removed as ineffective on their way to forcible retirement. To be "Stellenbosched" was to be so retired (the later equivalent was to be "bowler hatted").

Walrus (delving into trivia again).