Barrels or casks designed to be filled with alcohol, may be made tight by the application of the following solution: - Dissolve in a water bath 1 lb. of leather scraps and 1 oz. of oxalic acid, in 2 lb. of water, and dilute gradually with 3 lb. of warm water. Apply this solution to the inside of the barrel, where, by oxidation, it will assume a brown colour, and become insoluble in alcohol. This coat closes all the pores of the wood, and does not crack or scale off.