Yeast should always be kept in a glass bottle or a stone jug, and never in earthen or metal. Before you make fresh yeast, empty entirely the vessel that has contained the last; and if of stone, scald it twice with boiling water, in which it will be well to mix a little clear lye. Then rinse it with cold water, till perfectly clean. If you have not used lye in scalding it, dissolve some potash or pearl-ash in the rinsing-water, to remove any acidity that may linger about the vessel, and may therefore spoil the new yeast. If you keep your yeast in glass bottles, the water must be warm, but not hot; as scalding water may crack them: also melt some potash or pearlash in this water. The vessel for keeping it being purified, proceed to make your yeast. Have ready, in a kettle over the fire, two quarts of boiling water; put into it a very large handful of hops, (as fine and fresh as possible,) and let the water boil again with the hops in it, for twenty minutes or more. Sift into a pan three pints of wheat flour. Strain the liquor from the hops into a large bowl, and pour half of it hot over the flour. Stir it well, and press out all the lumps till it is quite smooth. Let the other half of the liquid stand till it is cool, and then pour it gradually to the rest; mixing it well, by stirring as you proceed. Then take half a pint of good strong yeast - brewers' or bakers' yeast, if you can get it fresh; if not, you must use some that has been left from your last making, provided it is not the least sour; stir this yeast into the mixture of hop-water and flour; put it immediately into your jug or bottles, and cork it loosely till the fermentation is over, (which should be in an hour,) and it will then be fit for use. Afterwards cork it tightly. It will keep better if you put a raisin or two into the bottom of each bottle, before you pour in the fresh yeast. Into a stone jug put half a dozen raisins.
All yeast is better and more powerful for being fresh. It is better to make it frequently, (the trouble being little,) than to risk its becoming sour by endeavouring to keep it too long. When sour, it becomes weak and watery, and tastes and smells disagreeably, and will never make light bread; besides being very unwholesome. The acidity may be somewhat corrected by stirring in some dissolved pearlash, sal-eratus, or soda, immediately before the yeast is used; but it is better to have it good and fresh, without the necessity of any corrective. Yeast should always be kept in a cool place.
Those who live in towns where there are breweries have no occasion to make their own yeast during the brewing season; and in summer they can every day supply themselves with fresh yeast from the baker's. It is only in country places where there are neither brewers nor bakers that it is expedient to make it at home. For home-made yeast, we know the above receipt to be excellent.
Sweet cakes, buns, rusks, etc, require stronger and fresher yeast than bread; the sugar will otherwise retard their rising.