Is that a paint or thermafoil bubble?

I don't think this happened in "seconds" but over a period of time. I doubt it can be fixed.

Anglo, maybe because it was hot coffee it accelerated the damage? Also surprised this damage would happen in "seconds".

Cabinets like that are typically constructed of MDF (high-end particle board) and it can permanently swell if subjected to moisture. Very hot moisture could greatly accelerate how fast this occurs. If you sand it and re-paint, it is likely to look worse than it already does. If you want to hide it, the simplest thing I can suggest is to find a small, innocuous shoe molding, paint it to match, and install it. In order to get it to fit well, you would need to trim off the bulge with a sharp chisel.

I wouldn't call MDF high-end particle board. MDF is sawdust mixed with glue and compressed. I'd call it a higher grade of cardboard. No furniture or cabinetry of any real quality is made from either.

As Kudzu says, water will wreck MDF fast. It's just like dropping your newspaper in the bathtub. In my experience, particle board is actually more durable.

Shame that this happened, but kitchens get splashed! Using material that isn't water resistant in a kitchen doesn't seem like a good strategy. This could just as easily have resulted from careless wet mopping..

If you have more time than money, I guess you could try making sure it's 100% dry (heater on low, blowing on it for 24-48 hours), sanding it flat with a sanding block using progressively finer paper (finishing with 320 or even 400 grit), priming it, final sanding, and spray-painting the whole cabinet side. But I'm not sure it's even worth the effort. Either covering it with molding or replacing the entire cabinet sounds easier and better.

Or consider this your opportunity to install better quality cabinets.

David-

You're wrong about MDF, both in definition - https://en.m.wikipedia.org/wiki/Medium-density_fibreboard - and its use in high quality furniture. I have seen many pieces of expensive furniture where MDF is used strategically to have the flattest warp-free surface possible. It is also stronger than plywood.

That must be a different grade of MDF from what I've seen.

The MDF I've worked with was grey. The color reminded me of egg cartons. It looked, felt, and tooled like very hard cardboard or papier mâché, or maybe Masonite. Wood screws didn't hold well in it.

I've seen the same grey cardboard-like stuff used as the frame of mass-market upholstered furniture.

The MDF in my cabinets is brown and very dense and does hold screws. Our cabinet doors are solid wood but the bodies are coated MDF. Never warped and have been in perfect condition for the last 30 years. Quite often it is recommended over wood for cabinet bodies.

DavidR-

I have no idea what material you're talking about. Whatever it is, it doesn't resemble any MDF I've ever seen or worked with in my shop.

While it's still wet, I would take a block of wood (2x4 or something) and gently position it in place next to the wet area. Actually, I would wrap the wood in wax paper first. Then I would press, and wedge, the block against the spot. Hopefully this would flatten the area. I don't think this would fix it but it might make it less noticable and easier to work with. It's worth a shot.

"I would take a block of wood (2x4 or something) and gently position it in place next to the wet area"

What will this accomplish?

Donna-

Once MDF or similar material gets wet like that, it's not going to flatten down again.

I've never seen the gray MDF that David is referring to. All that I've ever seen is brown. Hard. Very heavy.

MDF will hold screws. Poorly. Because the particles are so small.

Once MDF gets wet, it is trash. Swells up like the photo. When it dries, it just crumbles. . OP can try removing the crumbly stuff and patching with Bondo, sand, paint.

Or remove the cabinet, cut off the bad part, thoroughly seal the cut ends with oil based primer and reinstall it on some waterproof risers. Like strips of PVC 1x material.

If this cabinet is sitting on a counter^, this oops is just the first one. There will be more.

The grey whatever is not MDF. MDF is tan and there are many different grades. I can soak the MDF I use in a bucket of water for hours with no ill effect. Also if this happed very quickly it's most likley moisture causing the paint to bubble.

Thanks for the correction. I guess that the stuff I was told was MDF wasn't. :(

Hope you can find the quartzite.

Call around local countertop fabricators. Hopefully they'll have a left over piece called a remanent that will fit & save you some $. It's like a treasure hunt. I wish you luck.

That might not be MDF (pressed sawdust, smooth), but particle board (pressed wood scrapings, rough). MDF is higher quality and denser but still will be prone to water damage.

Particle board cannot be repaired by sanding, it only can be fixed if you cut the damaged portion and patch with a new one.

When it originally occurred, did you press on it to check it out? If it had give to it, it could have been a paint bubble where the paint became detached. If it was hard and had no give, it's very strange that it would completely flatten out.

I'd get some silicone on that edge pretty quick.

@russell63 Came across your thread as the same thing happened to me this morning. Spilled hot coffee and cabinet "bubbled" up like your picture. You mentioned yours disappeared - how long did it take? Do you think it just dried out and then disappeared? Thanks!!