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Hello fellow painters, have any of you ever experience a primer that refuses to come off when trying to strip paint off a model? I decided to strip some of my orks to try to see if I have "improved" since the last time I painted them and I used GW's black spray primer and the wont come off!!!

With my usual stripping method (ultrasonic cleaner with L.A.'s Totally Awesome) it takes at most a half day to remove every bit of paint off a model including army painter primer/Vallejo polyurethane primer, and the ork I am currently trying to strip has been in that ultrasonic cleaner for three days! The first day all the acrylic paint came off and I thought that maybe the plastic is just stained to a pure black as it had the primer on it for two years... But I almost gave up and just decided it was just stained I noticed two very small flakes of black primer in the bottom of my ultrasonic cleaner, is it possible that the primer somehow fused with the plastic and that is why it wont come off? Should I keep going to see if maybe in the next couple of days it will all flake off or say screw it and just prime it white like I was intending to do even if some of the details may get a little obscured due to the two layers of primer?

It is entirely possible that the primer has actually stained the plastic to the point where it will not come off.

I have had it happen and only since I started using an ultrasonic cleaner a few years back did I really sit up and take notice. It seems to be a side effect of the cleaners.

Use isopropyl alcohol 99% pure. The remaining primer will come right off with little brushing.

Wow I did not expect responses this quick lol, alright I will try the 99% Alcohol and see if that works. I assume that strength of alcohol can only be found in hardware stores like Ace Hardware right?

You can usually find 99% alcohol in any hardware store, pharmacy, grocery store, or several different department stores.

It isn't an industrial chemical but usually medical or science related.

Isoprop is the main ingredient of hand sanitizer. Requires some good brushing and scrubbing though, especially with primers.

I did a quick survey on various solvents here (last third of page 2):

http://www.dakkadakka.com/dakkaforum/posts/list/30/516912.page

If you work with Metal miniatures, THF or ethyl acetate will work better. With plastics, only Isoprop is realy safe (as the only ingredient. I give it a small shot of acetone, but dont overdo it, or you'll melt your miniatures down to a blob).

I dare say itle still work with 70% pure IPA, but I had 99.9% when I tried it... Can assure you that a plastic, or finecast, or resin piece is fine sitting in 99.9% IPA for upto 6 hours. (probably longer but thats where I stopped)

The primer started to come away with a little light scrubbing using a course bristled paint brush after 30seconds of being sat in the IPA.
I did find that using compressed air to quickly blow off and dry the mini after being scrubbed helped to not get a residue left on the pieces (what is dissolved in the IPA would be left behind) But rinsing with water or again with fresh ipa before it dries on might solve that too.

For metals I go for pure acetone, or lacquer thinners. works insanely quickly. but would destroy plastic or resin pieces just as quick.

I've found that IPA and another popular product; Fairy Power Spray (Dawn power dissolver) works best on the layers of paint applied over the primer, but the IPA works best on the primer itself. Each product seems to have its strengths, And nowadays I like to follow up a power spray stripping with IPA to finish it off. Gives me the best results so far.

So I added a bit of IPA 70% to the LATA in the ultrasonic cleaner and with brushing with a stiff brush every 30 minutes I noticed the solution is turning almost yellowy greyish so I think it may be working I hope.

(I also hope by mixing the two I did not create some sort of dangerous gas producing death fluid, I am wearing my respirator anytime I go for another brushing)

Its tough stuff. I am almost certain they use it on the bottom of the space shuttle.

It wasn't GW, but I once used a glossy black enamel primer when I was first starting out that later turned out to be wholly unremovable with my usual methods (simple green, etc). I only had one can so it wasn't a huge problem.

I now use the 99 cent spray cans from Lowes/Walmart and I love them. They dry fast, they wear fairly hard, they have good tooth, and if I have to strip them, they start peeling off within an hour in Simple Green.

Dot3 brake fluid will take it off and not harm plastics. It isn't a pleasant chemical, so make sure you wear PPE if using it.

That stuff will take off automotive enamel lacquer down to the bare metal.