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Hi again,

as you could help me very much with my recent question regarding wraithbone undercoat I would like to hear the wisdom of the elders again
I'm new to Citadel colors and Resin models and therefore excuse me if this is a dumb question. I got some resin models, one Carnodon from Forgeworld and another one APC from Models and Minis. I cleaned them with water and a bit of soap, washed them clean and dried them. Then I undercoated both with Citadels Chaos Black spray. I shook the can for 3 minutes, kept 20cm distance and sprayed in a continuous motion and got more or less nice results as usual. Yet for some reason I cannot really understand there are parts of the model (especially the tires on the Models and Minis APC) where the undercoat tends to flake away, even from relatively light touch as the weak, two sided sticky band I use to fix models on my "painting stick". They look like this:


Also when I tried today to airbrush some Ushabti bone as a test on the underside of the models (my airbrush skills are also nothing to write home about, but I try to improve), it also seemed as if the paint had in some regions problems to stick to the undercoat. While in most parts the paint distributed as usual, it looked as if repelled from those spots. A bit like I would expect if those were really waxy or fatty, but they don't look or feel like that.
I have the feeling I'm missing something or have made some kind of mistake along the way. Is this a sign that I did not clean the models well enough? Is there another reason I don't see at the moment?

What's the drama? Just respray those bits.

Regarding your airbrush, you possibly have the pressure too high. This will cause the paint to hit the surface in too liquid a state, and it quickly flows down the surface as the high pressure pushes more paint onto it. Alternatively you could have over thinned your paint, although this is less likely. Airbrush work really takes a lot of practice and figuring out your machines, techniques etc.

The tires already got two coates of Chaos Black, so before I put a third on I first wanted to ask here if I missed something along they way.

Regarding the airbrush: hmm... Okay, I will try it out next time.

Some resin dries to a slicker finish than others (often if it's super slick this is simply bad resin). When you wash them, are you brushing them with a toothbrush or something to ensure you're getting as much off them as you can?

Also - did you let the paint dry thoroughly before taping them on the stick again? Remotely wet/tacky paint will absolutely come off on tape.

Yes I used a toothbrush and I waited for the paint to dry. Even after two days, the paint on the tires flakes. As I surfed around a bit I read of similar effects, when there are still chemicals left on the resin. So maybe I did not scrubb enough. I guess I will try and scrubb them again and more thoroughly tomorrow and then undercoat again. Fingers crossed.

Ah I see. I thought that was just where you had the pieces on the stick or whatever.

That is weird. I've never seen even unwashed resin that won't take a good blast of a heavy ish spray paint

Yeah I've had similar issues with particularly greasy resin. At times it can be a real pain to get rid of thick release agent, particularly on large, flat surfaces. Sometimes a rub with a piece of dry kitchen towel or similarly very slightly abrasive material can help a little.

A little difficult to get a feel for the exact airbrush issue you are running into without witnessing it first hang, but what queen_annes_revenge said is what I was thinking; too thin or too high pressure.

I've had a lot of trouble with resin armor models in the past - WW2. I tried a lot of different things. I gave up on straight painting with a base coat. But a lot of primers exhibit the same thing you are describing. Agree with the previous poster that you need to not only wash the model but scrub it with a toothbrush. Don't know about your model but this can be a problem with models that have delicate parts.

The only primer I've found that consistently doesn't lift from resin is an automotive primer available in the US. I'm sure you have some equivalent, but I don't know what makes it stick. It's rustoleum filler and sandable primer gray. I decant it into a jar and then shoot it through my airbrush.

I don't know whether this helps, but I hope it does.

I have been told but have not verified that the Mr Surfacer line of primers will also stick to resin very well.

For resin, I always do a quick bath in Simple Green, scrub with a toothbrush, then rinse and dry. The Simple Green is a degreaser so will eliminate the mold release, which sounds like. The issue that is causin* your pr Blew.

Ok, I will look for it. As a first try I soaked the parts in water with quite an amount of dishwashing liquid and gave them an intense scrub with a toothbrush before rinsing and drying. Where paint flaked I peeled it off and where it was worst I even roughed the surface up a bit with sanding paper. I will try to undercoat again this afternoon and then test again with some basecolor and airbrushcolor on some part of the model, that is not too obvious. Fingers crossed.

If that still fails and for future resin models I will use degreaser.


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OK, the result was... not really convincing. I tested a bit on one model that was cleaned with dishwashing solution using a can of Zandri Dust. It stuck well on the first part I tested, but already on the second I got this result:

As you can see it looks like the paint is repelled from the edges of those panels.

Guess I will have to find a harder detergent and maybe soak the parts for longer in it. I'm a bit frustrated by now and just hope I not already ruined those models and will get some acceptable result in the end *sigh*. But that's life. Next time I get resin I will hopefully know better.

Aye, try a automotive primer as mentioned above. I use auto primers always, so that maybe why I've never really seen this issue.

Okay that's not normal at all. Did you soak your models before scrubbing them? I haven't worked with FW resin in years until I got my resin Warlord guns for AT and my primer went on perfectly.

Also are you positive the FW models you got were legit FW? The AT guns I got were new in the package but I ordered a Russ and Magnus off eBay to make a couple of small 30k armies and I swear they're recasts. FW builds their reputation and huge prices off their supposed quality and I've seen plenty of kits that don't look great. Recasters have almost no incentive to make sure they're using higher quality molds or mold release lubricants.

The amount forge world charge, their products should be perfect, with no release agent whatsoever. Its scandalous, but I digress

 queen_annes_revenge wrote:
The amount forge world charge, their products should be perfect, with no release agent whatsoever. Its scandalous, but I digress

in order to ensure production capabilities of the molds, you need a release agent to ensure no breakage on both the components and the mold.

I've never had a problem with my FW stuff. I do soak the parts overnight in a pretty healthy mix of room temp water and dish detergent. after they've sat i go at them with a soft(bristle) toothbrush and rinse them 2 or 3 times.

I meant they should clean the stuff off for us.

I got it from a hobby shop I once went on a discount in a bag with "Forgeworld" printed on it. But in the end... I have to trust the guy of the shop that he does not order from recasters and then packs it in an old bag. Would explain the discount price at least. So... lets say I'm 75% sure I got the real deal. I think in the future I will only order directly from Forgeworld, even if I usually prefer to buy from stores to prevent them from dying out.

But to answer Fajita Fan: no, I did not soak them over night, just for like... 15 minutes or so. As it is no big deal I will try that also. Lets see where I get from there.

Don't believe the hype. You're less likely to get mould release on recast stuff than the real McCoy. I have bought, made and painted both, and. At least in my experience that's been the case.

 queen_annes_revenge wrote:
Don't believe the hype. You're less likely to get mould release on recast stuff than the real McCoy. I have bought, made and painted both, and. At least in my experience that's been the case.

I have no experience with that to be honest, the parts I bought are still sitting in a bag since the spring. That said I soak what little FW resin I have overnight in soapy water, rinse with a toothbrush, spray, and pray.






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 queen_annes_revenge wrote:
I meant they should clean the stuff off for us.

And not send us obviously bent pieces with mold lines.

I give ALL resin casts a good scrub with an old toothbrush and toothpaste. FW is notorious for having mold release that sticks to models better than babygak to a blanket. You can even see the shiny patches where it is.

The tp is a fine abrasive that gets rid of any leftover residue from the mold release, and also keys the surface enough to give even primer a better foothold.

The 3rd party casters I've used have had way fewer issues with mold release and casting issues (and they even remove the gate and vent chunks before shipping, often cleaning the parts up quite well so you don't have to).

OP, I’ve had the same problem in the past, especially with Forge World models. The best way to solve it is to spray a coat of varnish over the model once it has been cleaned.

Step one: soak model in warm soapy water, scrub with toothbrush.
Step two: leave to dry fully.
Step three: spray with varnish/sealant, this provides a thin resin “shield”, this step ensures that if you have missed any mold release agent during the previous stage the paint will still stick as it should.
Step four: prime as usual, ideally with automotive primer.

The coat of varnish ensures that you won’t get any paint flaking off. It’s worth it for peace of mind!

Thanks, I will try it. I tried the car primer on the backside of the tires, but the result was not really convincing. Probably because I just wanted to test it and sprayed over the (washed and dried) older undercoat.
So currently I try my best to completely remove what is left of the old undercoat. Than I will again (for a third time) soak the models on dishwasher detergent and scrub them. Afterwards I will get some Varnish, apply it and follow up with Chaos Black. Lets see where we get from there. I will Keep you posted.

Some update:
I removed the older undercoat with a wire brush (which also roughed the surface up a bit - might help the paint to stick). Luckily the details are not that fragile that they would be damaged by this treatment. Afterwards I soaked them overnight in Dishwashing Solution and scrubbed them again with a toothbrush. As I still was not really convinced I gave them another overnight treatment with a heavier household degreaser.
I tested both - the carprimer and Munitorum Varnish - as "Pre-Undercoat" on the tires. Both worked well and now the Chaos Black sticks pretty good. The Carprimer I bought was a bit thick for my taste, therefore I went for the Varnish on the vehicles themselves. So far I'm quite satisfied, as the Chaos Black now went on pretty smoothly and I saw no puddeling.

I hope I come around to try airbrushing them again this weekend, then I can tell you more if this succeeded. But so far thanks for the tips, it definitely improved my situation.

You are welcome, I'm glad that the coat of varnish did the trick!

You could try wiping the bare resin down with 91% Isopropyl Alcohol (testing a small spot first). That might do an additional job towards cleaning the surface.

I know that many have this belief that acrylic doesn't adhere to it, but have you considered using an enamel primer?
In my experience(I worked for a giftware company using resin casting on a daily basis) scrubbing with a tooth brush and soapy water didn't do a damn thing. Personally it is more likely styrene rather than mould release,which is just a spray which we gave up using as it made no real difference.

Styrene bleeds through to the surface,hence the shiny finish. The only effective way to get rid of it was to use acetone. Now, I know that there are many types of resin and they may not like acetone but try it on a waste part of resin and see what happens/ten seconds at most should do the trick.

Enamel will take acyrlic paint; I have 2 original Land raiders painted way back in time when they were first released and they are undercoated with enamel, and the acrylic went on no problem and is still on.If there are still really sticky areas of resin the only real way to get rid of it would be to put some acetone on a cloth and give it a rub.

Forge world resin is gak. I've cast and recast. What you are doing with is likely not mold release but a chemical effect that comes when the resin mix isn't perfect. I've seen it. The perfectly smooth, like glass, surface. I've seen it on FW resin and actually had it happen now and then with various better resins. But you can tell the instant you pull it from the mold. If you have a glass surface, nothing will stick to it.

On a molecular level they act like the water repelling coatings they sell. It is actually exerting force on the paint pushing it away. The trick is to break up the surface or find a paint that isn't effected by the polar effects in play. Light abrasive like the toothpaste does the trick as the issue is microscopic rathe than that shiny smooth surface your eye sees.

 meatybtz wrote:
Forge world resin is gak. I've cast and recast. What you are doing with is likely not mold release but a chemical effect that comes when the resin mix isn't perfect. I've seen it. The perfectly smooth, like glass, surface. I've seen it on FW resin and actually had it happen now and then with various better resins. But you can tell the instant you pull it from the mold. If you have a glass surface, nothing will stick to it.

On a molecular level they act like the water repelling coatings they sell. It is actually exerting force on the paint pushing it away. The trick is to break up the surface or find a paint that isn't effected by the polar effects in play. Light abrasive like the toothpaste does the trick as the issue is microscopic rathe than that shiny smooth surface your eye sees.

No joke, I’m back in this thread with a Telemon dread that has a terrible surface finish. I soaked it in soapy water, Diet Coke, Simple Green, and Purple Power and scrubbed it with a firm toothbrush but this isn’t mold release, it’s the actual surface of the resin itself. FW told me to spray it with varnish before priming to see if I can put lipstick on a pig before they’ll replace the model. It’s way too cold outside now to spray but he told me temperature doesn’t affect sprays outside (say what?).

Vallejo brush on primer is sticking to other pieces I ordered that have the dull, matte gray color of normal resin but it won’t stick to this. I could barely get it to glue together because my Locktite glue kept seeping from joins. You can see the difference in finish with the AT Warlord gun by comparison.

Ick, I see what you mean.

So, I finally got to it, and now the paint seems to stick. Here is a picture after the first thin try of airbrush color. It is not perfect as you might see at the little panels on the left side of the photo, but I can work with it.




The second model (from Models and Minis) is a bit tricky, but roughing up the surface and some Varnish spray mostly did the job there too. I have some little spots on the floor and the side of ist turret where the paint just flows away, but I guess I will fix some jerry can or a a backpack there.