Hard paraffin 3½ lbs. 1600 grams
Carbon tetrachloride 10 gals. 40 liters
Before treatment it is preferable to immerse the racks which have
been previously used for developing, in a 1% solution of hydrochloric
acid for two or three minutes, wash for fifteen minutes and
thoroughly dry. The well-dried racks are then dipped in the above
solution and the excess liquid drained off, when the varnish dries
almost immediately. The varnishing should be repeated at intervals.