Pare half a dozen middle-sized potatoes, and boil them in a quart
of soft water, mixed with a handful of hops, till quite soft. Then
mash the potatoes smooth, not leaving in a single lump. Mix with
them a handful of wheat flour. Set a sieve over the pan in which
you have the flour and mashed potatoes, and strain into them the
hop-water in which they were boiled. Then stir the mixture very
hard, and afterwards pass it through a cullender to clear it of
lumps. Let it stand till it is nearly cold. Then stir in four
table-spoonfuls of strong yeast, and let it stand to ferment. When
the foam has sunk down in the middle, (which will not be for
several hours,) it is done working. Then put it into a stone jug
and cork it. Set it in a cool place.
This yeast will be found extremely good for raising home-made
bread.
Yeast when it becomes sour may be made fit to use by stirring into
it a little sal-aratus, or pearl-ash, allowing a small tea-spoonful
to a pint of yeast. This will remove the acidity, and improve the
bread in lightness. The pearl-ash must be previously melted in a
little lukewarm water.