What sticks to vinyl?

[WhiteDove01s]

First a warning: I don't get called the 'Mad Scientist' because of temper issues, and I also work mostly with cheap playline vinyl and not anything really pricey, so this may not be something you want to try. But... you were asking about what would stick, and so... I've been working for a long time (I keep tweeking) on a little old lady doll, starting with a Barbie head, and that meant needing a good way to do wrinkles (I started with a dremel!) and thicken out the chinline and make it more jowly, among other things. What I ended up using is Red Devil Brand All Purpose Caulk, tho I expect any brand of vinyl/acrylic (this one calls itself a siliconized acrylic) caulks might work. I have actually removed ol' Denia's head and swapped it onto different bodies after adding thickness to her chin and I've had no issues with anything trying to split off, and I did the initial additions years ago. It all feels like it was a normal part of the mold from the start, with the same flexibility.

Now, the bad part... caulk isn't really made for modeling. It holds fingerprints, will make odd little peaks when you move a tool away, is generally very soft and gooey when first applied, and dries to a nearly unworkable state with very little waiting around in the 'you can do stuff now' stage. And still takes a full 24 hours to completely cure. It's messy, not good for hand sculpting fine detail (tho I'm thinking of the possibility of pairing it with some kind of press mold), and more... it's plain white, so you'll have to essentially finish up by painting the doll's whole head in the hopes of having even coloration. (It holds paint just as well as any of the rest of a cheap Barbie doll's head.) It's very tricky to learn to work with...

On the whole, I'd second Maywong's suggestion of trying Sugru... but I have no personal experience with it. (Maybe someday. We're thinking of it for doll shoes that the caulk is just too goopy/soft to attempt. XD). But if you need something little, quick, and cheap on a cheap doll head, don't mind some messy fuss and have some dollar store practice heads to give it a try on first... if I have to give any Barbies pointy ears any time soon, or fill in a 'Dumb Barbie Grin' in favor of a thicker lower lip... I reach for the caulk.

[maywong]

I use Sugru all the time. It sticks to anything including vinyl. It doesn't smell, you can paint, cut, drill, and sand it. It will stays flexible even in hot or cold temps. The stuff is great.