I replaced the grout in my shower tiles the other day. I removed a good layer of the old grout and applied new grout on top. All looked fantastic for 48 hours until I used the shower. Now the grout has soaked up loads of moisture and is very wet to touch. If I run my finger along a grout line it comes off on my finger as if it's just been freshly applied. Any ideas on what I may have done wrong?? 😫
The grout has not cured. A couple of possible reasons are that perhaps it was old and deteriorated or it was improperly mixed.
Either way, at this point it's unlikely to cure properly. I'd pull it out and re-do the grout making sure to use fresh material that is mixed properly. Always follow the manufacturer's instructions for curing time and conditions.
When grout is applied per label instructions it should only take 24 hours for the grout to cure. I think they recommend an additional 24 hours before you can seal it.
If you had not applied any grout sealer the grout will absorb water (and become slightly darker), but it should not be soft or pliable after 10-12 hours. If it is still soft and can be molded than it will not likely cure and harden.
You should remove any soft grout (it will be easier than removing solid grout!) and vacuum the joints.
Starting with a fresh newly purchased grout powder mix and apply as stated on box instructions. Hint: you want to completely fill the grout joints which means pressing with rubber trowel until no air pockets remain. Wait for full cure as recommended by manufacturer and than apply grout sealer. Sealer can only be applied to dry grout so if it gets wet you'll have to wait to seal it.