Take 1 gal. urine, and add to it 1 oz. borax and 1 oz. salt.

How to Re-cut Old Files and Rasps - Dissolve 4 oz. of saleratus in l qt. of water, and boil the files in it for half an hour; then remove, wash and dry them. Now have ready, in a glass or stone-ware vessel, 1 qt. of rain water, into which you have slowly added 4 oz. of best sulphuric acid, and keep the proportions for any amount used. Immerse the files in this preparation for from six to twelve hours, according to fineness or coarseness of the file; then remove; wash them clean, dry quickly, and put a little sweet oil on them to cover the surface. If the files' are coarse, they will need to remain in about twelve hours, but for fine files six to eight hours is sufficient. This plan is applicable to blacksmiths', gunsmiths', tinners', coppersmiths', and machinists'files. Copper and tin workers will only require a short, time to take the articles out of their files, as the soft metals with which they become filled are soon dissolved. Blacksmiths' and saw-mill files require full time. Files may be re-cut three times by this process. The liquid may be used at different times if required. Keep away from children, as it is poisonous.