This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Second-hand corks find a ready market among some bottlers who want to reduce their cost to a minimum and yet have the prestige of using corks.
The quality of the beverage is not benefited, and many instances are known where the use of an unclean cork, of the second-hand variety, has contaminated the contents. Therefore, should this practice be followed, the bottler cannot be too careful in cleansing them, or too cautious in ascertaining the character of the places from which they have been gathered.
Second-hand corks, after lying for weeks around in bar rooms, covered with bad-smelling and fermenting vegetations, are sold to dealers, who subject them to a kind of bleaching process, run them through a smoothing machine, and sell them to bottlers, weiss-beer brewers and others, for use again. A cork may be ever so well cleaned, but the internal fissures in it always retain some of the vegetations referred to, and communicate its ravaging properties to the liquids they are used to preserve.
If every second-hand cork could be subjected to a sulphuric acid process, and then be placed under a steam pressure of about 300 or 400 lbs. it could be used with perfect impunity. A certain amount of danger lies in all second-hand goods that are liable to pass through dirt, filth and contact with disease, and bottles would be as fruitful a source of danger as any, were it not for the impervious nature of their material and the ease with which they can be perfectly cleaned.
A good way of cleaning second-hand corks, which will give satisfaction where the quality of cork is well preserved, is to soak them in an ordinary washing tub filled with water, to which half a pint of oil of vitriol (cone, sulphuric acid) has been added. By stirring them thoroughly at intervals for three or four hours, and rinsing them again in clean water, they will be found when dry to have regained their natural color, and be comparatively free from saccharine matter or other impurities.