Am looking to make a Neilson wine bottle look as though it is full (of red wine) and sealed - anyone have any idea what sort of paint might work on the inside? As in something which won't interact with the vinyl chemically, or crack and flake when squashed?

There are paints made specifically for vinyl, such as roofs, floors, siding, and automotive applications. But, there are different types of vinyl. This is probably uncharted territory you are entering, so experimenting may be at your risk.

I once used red tool dip to turn an empty Neilson ketchup bottle into a full one.
It worked great. It didn't hurt the vinyl at all.

Randi

Thank you - I'm not sure we have the equivalent in the UK other than in an aerosol spray; not sure how you'd apply that to the inside! Anyone know of a liquid version available in dark colours here?

Nielsen Magic sells what they call a "bladder" that can hole liquid, you can remove cap and pour out the liquid. The bladder expands and hold more then in the picture of the Liquid Insert Gimmick.

https://nnmagic.com/store/nielsen-vanish......gimmick/

I don't think the OP wants to pour liquid, but rather to create the illusion of a full, unopened bottle. The bottle as is would be a bit too transparent, even though it has a green hue to it. . Almost any opaque, darker color from red to black would achieve the desired effect of a bottle of red wine.

If you have the spray version of the tool dip, you may be able to spray it into a cup until you have sufficient quantity to pour it in and slosh it around to coat the interior. Maybe Randi will describe how she coated her ketchup bottle.

Yes, that's right; as stated, I'm looking to make it look as though it's full and sealed, rather than actually pour liquid from it. Good thinking re the spray/pour.

It's just a matter of getting the "good" stuff into a form that you can use. I do this all the time when I need to convert spray paint to brush-on when I need an exact color. Just be sure to wear a latex or nitrile glove when you spray into the cup. The overspray will get all over your hand if you don't.

Thanks for the tip Michael.