Corks are so important in many operations, that a little knowledge of the best methods of working them is indispensable. They form the best material for a holder for sandpaper in rubbing down flat surfaces, and they afford the simplest and most effectual means of closing bottles in many cases. Cork is easily cut by means of a thin, sharp knife, which should not have a smooth edge, however, but one set on a dry stone, moderately fine. After having been cut to nearly the right form, corks are easily worked to the proper size and shape by means of files. Holes are easily made through corks by means of tin or brass tubes, which must be thin and well sharpened on the edge by means of a file. The sharp edge being slightly oiled, is pressed against the cork and at the same time turned round, when it quickly cuts a smooth straight hole through the material.
When it is desired to make corks air-tight and water-tight, the best method is to allow them to remain for about five minutes beneath the surface of melted paraffine in a suitable vessel, the corks being held down either by a perforated lid, wire screen, or similar device. Corks thus prepared can be easily cut and bored, have a perfectly smooth exterior, may be introduced and removed from the neck of a flask with ease, and make a perfect seal.