1. Three to four weeks after the yeast culture has been added to the cider prepare the Acetic Culture in precisely the same manner as described for the yeast in paragraphs 1 to 6 above. See that all of the culture is removed from the bottle; rinse with a little cooled boiled water if necessary. Do not shake the jar while the culture is developing.
2. By the end of one to two weeks, a white, gelatinous film or membrane should be visible on the surface of the liquid. This is a growth of acetic acid bacteria and constitutes the "Mother of Vinegar."
3. When this acetic membrane is well formed, which will require about two weeks, with a clean sliver of wood, previously dipped into boiling water, remove the membrane from the jar, but do not lay it down; pour the contents of the jar into the barrel of cider, now fermented, to which the yeast was added some five or six weeks before; next drop the sliver with the attached acetic film into the barrel through the bung-hole. The wood will serve to float the acetic membrane on the surface of the hard cider and thereby hasten its development by keeping it in contact with the air.
4. Keep the barrel at 65 degrees F. to 75 degrees F. till the vinegar has formed.
5. When vinegar of satisfactory quality has been obtained, in three to six months, draw off and store at a cool, even temperature in casks which are kept full and tightly bunged.
6. Both of these cultures can be propagated indefinitely by employing a small portion of the jar cultures in the same manner as the original bottle starters.