HELP! Acrylic Paint Coming Off my Model

Proper surface preparation is critical. Wash the sprues before doing anything to get the mold release oils off the plastic. I do an additional wipe with rubbing alcohol and I've also have got into the habit of priming with Tamiya's fine surface primer. You can use flat white, but I would suggests a longer cure time. Acrylic paint dries to the touch very quickly, but depending on the temperature and humidity, it could take a week or even longer to fully cure. Once fully cured they are every bit as tough as enamel.

 Hmmm....did you prime? If you didn't. there's your problem.

Armor model manufacturers seem to be only ones so far that have figured out how to mold plastic without some nasty, diabolical release agent. I can generally spray an acrylic over the bare plastic and go to town on it, weathering and such, with no problems.

Autos and planes though--and I would guess Sci-Fi too--forget it! You MUST prime these models or reap the whirlwind! I'll bet that that's your problem;.

What Bill said.

You cannot use acrylics just as if they were the enamels with which you are overly familiar. Different beast entirely.

Because acrylics dry to touch rapidly, tip dry and applying a coat that is too dry is more easily done. Use an acrylic retarder (about a drop mixed with your reducing solvent, then added to the paint).

I recommend cleaning the model surface just before painting with either Windex, a surfactant cleaner, Simple Green solution (rinsing necesssary) or at least an alcohol wipe with 90% isopropyl or straight ethyl (Everclear) or denatured alcohol. Do not use common rubbing alcohol (70% isopropyl).

If you are using Tamiya acrylics, they don't bond too well to primer until they are completely cured. one thing to do, if you've used primer, is to look at the paint that stuck to the tape and see if it's primer colored. Also look at the model and see if the area where the paint came off is still primed or if it's bare plastic. Either one will give you a little insight. If the primer came off, the plastic wasn't clean, as has been noted above. if the primer stayed on, your flat acrylic didn't dry enough.

As was mentioned, the Tamiya fine primer is really good stuff, I haven't found better. Expensive sure, but really thin, really opaque and really sticks.

Triarius

What Bill said.

You cannot use acrylics just as if they were the enamels with which you are overly familiar. Different beast entirely.

Because acrylics dry to touch rapidly, tip dry and applying a coat that is too dry is more easily done. Use an acrylic retarder (about a drop mixed with your reducing solvent, then added to the paint).

I recommend cleaning the model surface just before painting with either Windex, a surfactant cleaner, Simple Green solution (rinsing necesssary) or at least an alcohol wipe with 90% isopropyl or straight ethyl (Everclear) or denatured alcohol. Do not use common rubbing alcohol (70% isopropyl).

The masking material makes a big difference as well. I have masked over acrylics using Tamiya tape without using a primer coat and had no problems with Tamiya acrylics. I do however scuff the plastic first with a Scotchbrite pad, wipe it with Plastic Prep or 91% Isopropyl alcohol and then airbrush so that the surface has some "tooth" as well as being clean. So as the others have said I recommend you prime first or scuff the plastic in some way to allow the acrylic to grip the surface.

Thanks guys for your help. One more question, can you first spray enamel base coat then spray acrylic over it? 

Tanis103

Thanks guys for your help. One more question, can you first spray enamel base coat then spray acrylic over it? 

Yes, you can, provided the underlying paint is fully cured. Leave it for at least 24 hours, preferably 48, before applying the top coat.