Hi.  We recently touched up a blue-black slate counter that the owner had been treating with linseed oil. The linseed oil created a heavy build up, which we removed and then applied a color enhancing impregnating sealer.  The result was great.  However there were some white rings and spots that were in the stone (within the stone, not on the surface - like stun marks in marble).  After a couple of weeks the white spots are coming back and I am going to apply a little more of the impregnating sealer to see if that subdues them.  But I am wondering if there is some sort of treatment I can use on these little areas that will be more permanent and will not require constant touch up.
Thanks much.

From the desk of
Baird Standish
Managing Partner
Facility Specialists, LLC
1616 Walnut St.
Philadelphia, PA 19103
Phone: 215-732-7505
Fax: 215-546-9160