Help identifying bathtub finish

Question

We just moved into our home (built in the 1950’s) and noticed that cracks were forming between the wall and edge of the tub. In some places, water seeping into these cracks was causing the tub finish to become slightly malleable. Before sealing the cracks with caulk, we started to remove the finish in the area shown by the red rectangle thinking it was old caulk, but then realized it was not. The right image shows what we found as we cut out the loose material.

The “finish” is only about a millimeter thick. The top white layer feels like an eggshell. Beneath that, there’s a cream-colored layer that feels rubbery. Below that is a thin layer of darker gritty material that feels like cardboard when wet and cement when dry. Finally, the exposed ivory-colored layer beneath the finish feels much harder, and we suspect it might be the enamel of the original tub. From looking in the access panel, the tub appears to be made of cast iron.

We are looking for help in identifying what type of refinishing might have been done to the original tub. We’ve talked to a plumber who had never seen anything like this in their 50+ year career. As for fixing the damage, this plumber suggested epoxy to fill the gap, but we’re not sure if this is appropriate since we can’t identify the construction. Would enamel repair be more appropriate?

Thank you for any insight you can provide!

Answer 1

What happened is your tub was refinished, (re-enameled). However the prep was not done well. The old caulk was allowed to remain and was enameled over.

The junction between the new enamel and the wall surface then cracked. ( The tub should have been cleaned of any caulk, then enameled and caulked.)

Once cracks appeared, water infiltration caused the area to deteriorate.

You can try to carefully remove the old caulk, but that may cause more enamel pealing.

                          OR

You can try to clean the area around the tub/ wall edge. Tape off the wall and tub to make a nice straight line and apply a bead of polyurethane caulk, (It is firm but remains flexible.) That will seal the tub to the wall and should prevent future cracks for a number of years.

Answer 2

The old one could have had multiple coatings on, over the years.

I think you need to discuss this with people who do resurfacing and re-enameling of bathtubs. The tubs can also be repainted. But if it is really cast iron, then re-enameling would be longer lasting.

Except for repainting, I suspect you have to remove the tub and take it to them.

Search terms are "recover bathtub" or "refinish bathtub"

Answer 3

The top white layer feels like an eggshell. Beneath that, there’s a cream-colored layer that feels rubbery. Below that is a thin layer of darker gritty material that feels like cardboard when wet and cement when dry. Finally, the exposed ivory-colored layer beneath the finish feels much harder, and we suspect it might be the enamel of the original tub.

Sounds like the tub was visited by one of the outfits that drops a thin plastic overlay in the old tub, based on the description of the top two layers, anyway. Thin plastic shell and rubbery underlay I know for sure is those outfits, perhaps the cardboard/cement layer helps to fill imperfect fitting of the overlay to the original tub.

Since their whole schtick is doing it in place without tearing up the bathroom, quickly, the joint of that new overlay to the old tile (or untiled wall, in your case) is a weak point, as it won't be properly lipped under the wall surface.

Epoxy is probably your best bet short of replacing the tub.

I looked into having that done to a failing tub once. Turned out replacing the whole tub was a LOT less expensive than hiring them, and they wrote themselves all sorts of loopholes on the quality of work in their standard contract, so they could get paid large sums and you end up with leaks and it wouldn't be their problem. So I replaced the tub.