Woodburner going in next week so need to seal the recently laid tiles on the hearth as this weeks rain and soot down the chimney has proved that unless they are sealed they are going to stain very quickly!

They are a ceramic unglazed tile made to look oldy worldy chipped and discoloured marble (perhaps?)so no problems if the sealant discolours them as it willjust add to it! Area that needs sealing is about 1 square meter so a bit reluctant to get a 5l £40 tub of sealant………………so what I am wondering is if there is a cheaper DIY way of sealing these tiles, a cheapskates way??

Thanks