"Priming plastics problem" Topic

I am taking a break from painting armies at the moment but for something to do I decided to paint the figures that came with the "War of the Ring" boardgame. So, not painted plastics since Aifix 1/72nd scale some forty odd years ago so read up on it and did all the prep including washing in a mild detergent to get rid of any release agent.
Started on the good guys which are all either a softish blue or grey plastic and primed with a Plastikote Flat white spray.
No problems and well on the way to finishing them so decided to prime the bad guys which are the same kind of softish plastic but in red.
Now for these I split them into a white undercoat exactly as before or a Valspar(UK) fast dry flat black and this is where the problem comes in.
Three days after spraying the white primed are still a touch tacky but the black ones are both very tacky and gloss except the Nazgul which are a slightly harder grey plastic. They are already dry and matt in finish.
They were all done at the same time, on the same day and in light coats repeated over a period of several hours.

The problem seems to be with the red plastic figures but I have no idea why or how to resolve the issue unless it is a case of waiting a lot longer for them to dry. A bit odd but I usually paint 15mm metals and they dry undercoated in hours not days.

Any thoughts?

Pick up a can of Krylon Fusion, white satin. It is designed to bond to plastic.

Another option that works well on soft plastics is Gesso.

Why don't you try painting over that? I had the same issue with a few Bones miniatures. I just paint over, and haven't had any problems.

spray paint and plastic do not mix.
gesso is your buddy.
even krylon fussion has issues with some plastics.

Krylon Fusion has worked great for me.

I've also used Rustoleum Ultra Cover, allegedly designed for plastics but remains tacky to touch. However, painting over the tacky primer worked and it cured fine. There was a little colour blending with the tacky primer.

OK, I'm in the States… what the heck is "Gesso?"

Gesso is a primer for canvas (and probably anything else). You will find it at any art supply store or teacher supply store. You can also order it via mail.

Hobby Lobby, Joanne's, Michaels all carry it…

It typically comes in white or black.

Cleans up with water, great stuff!

The tackiness will disappear after a couple of days, if you can get plasticote black that works though if not shaken for ages it can go glossy and it isn't as good as teh white so you might have to spary white and then give them a coat of matt black with a big brush ( I recommend Humbrol acrylic for this)

Been four days now and still tacky so will have to go with Beowulf's suggestion and paint over and hope for the best.

Thanks for the input, one and all.

A week on and still tacky but Beowulf spot on and painting over works.

Can anyone answer part of the original question though, as to why this type of red coloured plastic react so differently to the same paint that went on grey or blue plastic successfully?

Might help anticipate any problems in the future.

Not a chemist. Sorry. I can vouch for Gesso, though. I have used it to prime plastic miniatures before, with great success. It is a brush on, but it works quite well. Cheers!

Would Vallejo Polyurethane primers work?