Best hinge for a door that's "invisible"
 

What sort of hinge is available for a door that opens into a room that is ~2.5" thick, and 18"x44" that won't (or minimally) show (wall and door will look like drywall)? I know there are cabinet door hinges that are designed for inset doors on frameless cabinets, but I am thinking that those wouldn't work for a door that's 2.5" thick. Correct me if I'm wrong. If I have to, I'll go with a regular thinner hinge in white. But it seems like there's probably something out there that I just don't know about.

There are special hinges for doing secret room doors that might work.

Look up SOSS hinges as well.

You want a pivot hinge. The cabinet hinge likely won't manage the load of an 12" x44" door with sheetrock on it. The pivot hinge mounts to the floor and lintel of the frame and can carry pretty large loads.

https://www.swingingcafedoors.com/stainless-steel-hidden-door-pivot-hinges/?sku=SSHDPIVOT-S-O-1&gad_source=1&gclid=EAIaIQobChMI6uv_76SRiQMVhtTCB B3m3RLZEAQYAyABEgLRqPD_BwE

I'd found hinges like those online, but didn't think they'd work for a thick door, but SoSS definitely makes them for doors +2" thick.
Yep, I'd wondered about those as well, but didn't know the name of them.

2.5" door is going to be heavy.
Might look at piano hinges (runs the entire length)

It's going to be mostly hollow (and about 1/4 size of a regular door), so shouldn't be too bad.

See the picture below. They're fantastic.

You forgot the picture.

Or did I? :D

I am not sure about other brands but Soss hinges are the ones we use for that application.

lmao!

Bingo!

That's what I used on hidden shaker style panel door to pick up the storage space under a set of stairs. 4 hinges on full height panel. Had the hinges laying around, still holding up after 8 years.

Are the hinges for your knee wall doors?

Yes

Cabinet hinges will not work on a thick door. You can get them for 1" door and that's usually the max. I am not sure if they make then for thicker doors? Any thing thicker, use the Soss hinges or a piano hinge and you really want to yank your hair out, do the pivot hinges.

I feel like the SOSS may be the best option. Piano would be second (way down the list). Pivot would be cool, but I can see those being a PITA.

Some of the cabinet hinges that I found looked like they were the same type/style as the SOSS, just probably cheap knock-offs.

Are we talking about the same SOSS hinges? They must be mortised in with a router. Pretty heavy duty. They are sometimes used in commercial heavy duty doors. Pivots aren't too bad to install but they are different and requires the door to be perfectly plumb and a good jam that is plumb and true if not that gap will read like a book.

Yeah, looks like the SOSS stuff is on Amazon, and there are also similar hinges on Amazon
https://www.amazon.com/TamBee-Hidden-Invisible-Concealed-Adjustable/dp/B07WT3C7TJ/

the ability to adjust is huge Those should work great.