I’ve seen a few posts questioning types of tile adhesive. For clarity. Ready mix in a tub needs air to dry. It’s not reliable but if you do need to use it - never use in wet areas, as it will break down over time. never use on floors and only use for ceramic tiles - as the backs are porous so absorb the moisture to help drying out. Never use ready mix for porcelain tiles. It will never dry as porcelain is not porous and 3 days or 3 weeks later you will be scraping it off still not dry and starting again. For wet areas, porcelain and floors always use dry mix. For floors flexible is best. Dry mix is cement based and uses a chemical reaction to cure (like concrete) sets hard as nails.