Dave

If it was a topical sealer used then you could just strip it and use any sealer....but seen as it is an impregnator then it is not worth the risk of cross contamination of products.....It might be ok it moght not.....So that's why i said just to use HG again..seen as you know what was used.....some cleaners will clean deeply but is it worth the risk..especially with a product like black slate that will show any reaction...?