Repeatedly cleaning off the face of Bath or other stone by rubbing, glasspapering, etc., is to be deprecated, as it removes the natural skin, and, by opening the pores of the stone, makes it absorbent. Treatment with Fluate or the Szerelmey liquid will give the surface of the stone a siliceous skin, closing the pores, and making the stone non-absorbent. Neither of these preservatives will appreciably alter the colour of the stone, although it is probable that in time the stone will become a little darker. An alternative plan is to paint the stone with a flatting coat of white lead mixed with turps and a very little linseed oil; this leaves a dead surface without gloss and not unlike that of distemper, and is also a preservative.