If I seal a stone with an impregnator and it somehow becomes stained, will a poultice work?

Yes, it should work as long as the stain occurred after the stone was sealed. If the stain was present before the sealer was applied there is a good chance that the stain will be sealed into the stone making removal difficult. If this is the case the sealer will have to be removed by using strong solvents such as methylene chloride and than apply a poultice to remove the stain.

TIP After a poultice is applied to the stain you may find that the stone discolors. If this is the case it may be necessary to reapply more impregnator.