How soon after grouting can I apply the second coat of sealer on your Brazilian slate tiles?
A great question in this modern age of adhesives that can fix tiles and allow grouting within a very short space of time. However, sealing is slightly different in so much as the process should only be carried out on surfaces which are scrupulously clean and most importantly completely dry.
It would be highly unlikely that the tiles would have fully dried within 2 hours of grouting to allow for the 2nd coat of sealer to be applied with confidence. Impregnating sealers rely on being 'absorbed into' the stone for them to work effectively, residual moisture within the tile and the grout will diminish the sealers ability to be absorbed resulting in an impaired finish.
It's also worthwhile noting that there are a number of factors which will inevitably have an impact on the drying times of newly grouted surfaces such as the widths and depths of the grout lines and also the ambient air temperature of the room.
In short Chris, ideally the grout would need to fully cure before the sealer is applied and this usually takes approximately 24 hours but do check with the manufacturer of the grout for advice on full cure times for the particular product you are using.
I hope this answers your question Chris but should you have any further queries, please feel free to call our office on 01283 730388.