On Sunday, February 4, 2018 at 8:41:32 PM UTC, N_i_c_k wrote:
Hi, I'm thinking of applying this[1] or similar to a limestone
fireplace that hasn't got any sealant on it yet. Anyone done this, any
warnings or recommendations?

Thanks

1. https://www.extensive.co.uk/mn-stainstop-500ml.html
--
Nick

IME sealants produce a "wet" look, which may not be what you want.
Usual guff on the website about an "impregnator", and then an invisible, yet breathable, film. Eh?
Also, silicone tends to collect grime.
I've used Thomsons Water Seal on outside brickwork and, from memory, that doesn't form a film