Yesterday I tried airbrushing my Arizona model with MM Acryl 5-L Light Gray. It seemed to go down fine but even after several hours of drying any lightest touch just lifted the paint away. I did clean the plastic beforehand with alcohol and a clean cotton cloth to get rid of mould release agent and fingerprints. I didn’t prime the surface, don’t have a primer for the purpose, just a lot of MM enamel and Tamiya (and now MM) acrylics.
Help?
Yes, MM Acryl colors pretty much demand a primer coat before hand. Their adhesion is weak far too often. A dissimilar primer of a more durable paint type such as enamel or more durable acrylic will improve that.
Primer!
In this case take the plunge and strip the model.
You have no choice.
Then prime with a color that’s neither color of plastic or final color.
White
Use Tamiya Fine Grey Primer and thin the MM Acryl with lacquer thinner and you’ll have no problems.
I AB MM acrylics often. What works for me is: I seldom prime. Before painting, I ‘scrub’ the model with an old stiff paint brush dipped in Tamiya lacquer thinner. It has never damaged the plastic, dries fast and seems to craze the surface just enough for good paint adhesion. Masking with Tamiya tape yields good results. Your mileage may vary.
Using alcohol to clean it may have been the problem. I used it to clean a resin figure years ago, and could never get any kind of paint to dry on it, after that. I tried both enamels and acrylics but neither worked. I ended up throwing the nice figure away. Since then, I only use dish soap and water.
I use the Tamiya fine in the rattlecan,real easy to use,or Mr Surfacer 1200 in the rattlecan if I could get it
Hmm, I clean my polystyrene models with Plastic Prep, which contains isopropyl alcohol. So I don’t see alcohol causing problems assuming you let it dry before you paint.
Personally, I have not had MM acryl rub off like that, Tarasdad. I agree that primer is a must for water-based paints. It definitely helps adhesion. Of course, poor adhesion can have many causes: bad bottle of paint; paint not mixed enough; high humidity; incompatible thinner; etc.
Curiously, I once had the exact opposite experience with MM Acryl. I painted a Mustang spinner with Acryl guards red and insignia yellow, without primer. I didn’t like it so I decided to strip it and try again. I tried to strip it using masking tape, as I head many stories of Acryl peeling up when masking tape is removed. But I found that even with the stickiest tape I had, not one speck of paint peeled off that spinner. I have no idea why that paint job was so robust, but I wish it was like that all the time!
Chris
Great advice here.
Just wanted to chime in and mention that I had same problem as you on my first build back from hiatus. Primed with Model Master grey primer, to find out later it isn’t really a primer, just a color called grey primer. If Model Master has a real primer available, I’m not aware of it.
Point being, if you are going to prime, use on of the good primers mentioned above. I’ve tried each one, never had an adhesion problem with any of them.
To repeat myself, I recommend using a primer that is NOT too close to the final color. If you are painting the ship 5L which I think is your plan, don’t use gray primer. You’ll have a hard time checking your coverage, esp. in hard to get at nooks like under the masts. Better to use white- that way you can tell when you’ve totally covered it. For the same reason, using gray primer on gray plastic makes it harder to see if you have total primer coverage.
White would be a good choice. And as always, run a test of primer/ finish paint on something you don’t care about before committing to your fine model. Stripping a model once is a pain, stripping it twice is a tragedy.
I really never understood the reason for using a different color primer. Thanks for that, GM.
It’s too common sensy, probably why it had evaded it thus far. Makes perfect sense now.
Here are another two pennies - Regardless of how clean we may think we have prepped a surface for paint, it really can be difficult to get it absolutely clean. Mold release and contaminants other than that, could have gotten on the plastic while handling, prior to being boxed at the production facility. Before I even begin a build I remove fuselage/wing parts from sprue and take to sink, moderately warm water soap and brush cleaning with THOROUGH rinse, both sides, dry with clean kitchen towels.
When I prep/clean for painting, I’m careful to ensure that with each pass I use a new cloth or tissue, and I never place the cloth over the pour spout of the container to dampen, too easy to contaminate the whole can of liquid. I pour liquid into a small separate cup and refill as needed. My most used prep liquid is either alcohol or Prep Sol, again changing tissues AND LIQUID with each pass. Following second pass I just let them air dry, blow off with compressed air to remove any dust prior to spraying paint.
I agree completely with Fly-n-hi, a good prime coat works well in just about all cases. It was a great tip to thin acrylics with lacquer thinner, (but NEVER with Vallejo products,) it does really improve the “bite” and ability to avoid lifting when masking. Best of luck, hope you have good results in the future.
Patrick
I used to clean my models before painting. Not any more. I prime with Tamiya or AK primers and they simply stick to the plastic no matter what.
Washing your hands well before modeling helps too, especially in hot summer weather. Oils left when sweat evaporates is bad on paint and even primer adhesion. And if you do something messy while modeling, wash them again. I find I get paint thinner on my hands when mixing paint and have learned the hard way that I need to wash them before doing anything else on the model 
I took Don’s advice about washing hands often a little over a year ago, and it has paid dividends.
Thanks again, Don.
Most of the time when airbrushing I wear either nitrile or white cotton archivist’s gloves to keep skin oils off the plastic. I’ll use the cotton ones when handling a painted model that hasn’t been clearcoated for the same reason. Didn’t do that on my Steyr build and it shows, but actually adds a bit to the grungy weathering on the panzer grey paint.
I’m going to stop by (or have my wife stop by if I can’t go) the LHS to see if they have Tamiya primer. I’ve also considered some of the higher quality primers from Vallejo, AK or Mig. The latter just made my blacklist though so is no longer in consideration.