Examples from the Web for pearl ash
If you are apprehensive of its becoming sour, put into each bottle a lump of pearl-ash the size of a hazle-nut.
Pearl-ash water is also good to remove putty before it is dried on the glass.
Beat four eggs very light; and add them to the mixture with a salt-spoonful of pearl-ash melted in a little lukewarm water.
When perfectly dry, iron it very smooth; the pearl-ash water turns it a dark color, but washing will efface it.
The pearl-ash will remove the sour taste, and increase the lightness of the cakes.