Among other processes which have been tried are -

Solution of Baryta followed by solution of Ferro-silicic Acid so as to fill the pores of the stone with an insoluble ferro-silicate of baryta.

Solution of Baryta followed by solution of Superphosphate of Lime producing an insoluble phosphate of lime and phosphate of baryta.

Soluble Oxalate of Alumina applied to limestones produces insoluble oxalate of lime and alumina.

" These three processes last alluded to all possess the advantage of producing by the changes they undergo within the structure of the stone an insoluble substance, without at the same time giving rise to the formation of any soluble salt likely to cause efflorescence, which necessarily attends the use of alkaline silicates," 1

Temporary Protection Of Stone Surfaces

During the erection of large buildings the surface of the masonry built in the earlier stages of the work is smeared over with a sort of thin mortar, so as to preserve it from atmospheric influence, and to make it easier to clean down.