I have two fireplaces with Cotswold Stone backing and rendering but heavily stained by tar/,fire marks , Wire brush does no good . What I need is to cover tar stained stone with a highly heat resistant masonry type paint ( stone coloured ) as new logburner will be placed in fireplace , where back of log burner will be about 3-4 inches away from surface of stone hearth , Please advise whether I can use a paint directly on existing stone/Render , or do I need to re-render and then paint many thanks James m-s
For this application assuming the stone is porous, clean, dry, sound and prepared as detailed in the technical data sheet you could consider Tikkurila Muuri.
While we have no experience of it being applied to Cotswold Stone assuming it has some porosity and with this in mind would have thought it would be ok to paint but as ever in these circumstances a small test would probably be advisable first to make sure it adheres ok.
With reference to the heavily stained issue however this does pose a potential problem in as much that the contamination could cause a few issues such as discolouration of the Muuri (bleeding) and potentially may also impair adhesion resulting in flaking and general loss of adhesion if this cannot be removed prior to application.
This paint can withstand upto 300°C in white or upto 180°C in a tinted colour.
This is not suitable for direct flame contact.