Acrylic paint lifting

MM Acrylic primer requires a lot of surface preparation. I prefer using their enamel or lacquer primers which work great. Once primed and fully cured, MM Acrylics adhere realy well, never had paint lifting problems.

MM Acrylics have very poor adhesion and durability properties in my experience. They certainly require a good primer coat at least to improve their adhesion.

I tried using the Model Master Acrylic white primer the other day on an aircraft model.  It sprayed really nicely out of the AB; however, that is where the "nice" part stops.  This stuff lifted even using Tamiya tape.  I went through and light-sanded the entire model to feather out the areas where the primer lifted.  I then recoated the model with the primer and let it sit for another 24 hours.  I then went back and painted the model using Model Master Acrylic paint.  I am able to scrape off the paint and primer together with my fingernail without any effort at all.  I am now going to attempt to removed all of the paint and primer and start over.

I've seen several people mention using Krylon primer; both decanted for AB use and some straight out of the rattle can.  I was wondering if anyone knows whether or not you could add a drop or two of laquer thinner to the acrylic primer to give it some bite on the plastic?  I realize that you probably dont want to use too much.

I just picked  up Badger's new primer and so far it's working out pretty darn good. I posted a review on youtube. Check it out and see if you're willing to give it a try

http://youtu.be/SDm3BhnTQ5A

I use the 3M drafting tape& press the tape onto a cloth several time to remove most of the adhesive; it works  'most' of the rime

I know MM sells a flat gray primer in the small rattle cans as well but thats either enamel or lacquer based.  They also sell an acrylic primer in the small bottles which I wouldn't touch personally. 

It not only depends on the paint and curing time but the masking tape.  I have different widths but I use either Tamiya Masking Tape or 3M Blue Tape for Delicate Surfaces and I've never had an issue with paint lifting off.  As long as the primer & topcoat have cured and you pull the tape off slowly & gently it shouldn't come off.  

If your paint is lifting off make sure the primer coat underneath has cured properly.  I use Vallejo Primer for small parts like cockpits and the cheap enamel rattle can primer for the main body,fuselage, etc.  And I've never had an issue.  Of course I use Tamiya/Gunze paints thinned with lacquer thinner.  But I've never had an issue with Vallejo except 1 time and that was b/c the primer coat wasn't cured underneath.  

Model Master sells a White and a Gray Acrylic primer in the bottles.

Vallejo sells a PolyUrethane primer in 60 ml and 200 ml bottles. At least one of the Vallejo 17 ml "primers" is really just the color of primer, sort of as seen on real cars, not an actual primer for plastic models. (Model Air 71.097 Gray Primer is only a paint color)

Rex

both acrylic

Are the Model Master and Vallejo primers acrylic or enamel?

I have no luck either with acrylic primers as they just lift off when removing masking. The acrylic paints don't have the bite to stay put. I have been decanting Krylon primers and using them in my AB and have been getting excellent results specially on PE parts. This stuff provides a sound foundation for top coats.

Chrisk-k;

Can you sand the AK primers with a more standard grit paper?  Just wondering what the difference is from Vallejo's primers?  Vallejo's don't have any smell either.

John

Chrisk-k, I have read the mention of AK primers before on here,,,,it might have been your post, in fact.

I plan to give them a try the next time I buy primers. I am using the Vallejo PolyUrethanes now, but, I don't use them as anything except as a coat just before the Acrylic paints. I do all of my sanding before I spray any PolyU on the model.

a USA source for AK is

 www.megahobby.com/thinners-primers-and-clear-cotes-for-plastic-model-kits.aspx

part way down the page (I use Mega a lot )

Rex

Vallejo primers are not sandable unless you use ultra fine grit sandpaper. But anything is sandable with 3000-grit sandpaper.  

I love AK acrylic primers. Their performance is on par with Tamiya primers and yet they have zero smell.  Sprays very well @ 20 psi and very easy to clean with IPA or Windex.  The only drawback at this moment is because they are new, they are hard to find in the US.  

Just want to add that I have not been able to sand the acrylic polyurethane primers.  It just comes off in pieces which I read about happening.  I have then applied a second primer coat and it levels almost perfectly.  For my armor the sanding of seams really isn't an issue.  for aircraft that might have a seam that I want to prime and check I use good old Tamiya fine surface primer in the can.  A bit expensive, but the best all around.  Can't use it indoors for me like the Vallejo.

Since this came up I tried just spraying Vallejo Model Air RLM 66 on the inside of an Fw-190 kit from Eduard I have going.  Let it dry overnight and then tried some tape and Blu-Tac and nothing came up.  That was with no primer of any kind.  I had read the Model Air bites well.  Not sure I will forgo primer on the outside but maybe for the inside stuff that doesn't get handled and masked it will save some time.

John

Just wanted to chime in that I've been using Vallejo Air and Vallejo Model Color over the Vallejo Acrylic-polyurethane primer as well for 9 or so months, haven't had a problem. So far anyway.

That said, using a primer with even more bite makes  sense to me.

I don't know of anyplace where I can get the PolyUrethane primers in person. But, if you are in the USA, here is a pretty good place to get them by mail.

www.scalehobbyist.com/.../browse.php

ignore the 17ml size, the 60ml and 200ml are the PolyUrethanes by Vallejo.

hope this helps

Rex

Thanks pilotjohn, anyplace local carry the polyurethane primer. I have a hobby lobby close by that carries Vallejo paints but not primer

I know that many folks get different results, but I am working on a kit and used Vallejo acrylic polyurethane primer followed by model master acrylics.  Did a three-color cam scheme and used both Blu-Tac and Tamiya tape for masking and nothing lifted up.  Left the Blu-Tac on for a day and a half between colors.

I let the primer cure 24 hours and have never had a problem with it.

John

Yes, I suggest going with a dissimilar primer (non acrylic) with more tooth. Humbrol, Mr Surfacer, Tamiya Lquid Surface Primer all have given me good results.

Vallejo simply doesn't bite plastic.  Instead, it creates a rubber-like coat over plastic.  There's a long thread about it at Armorama.  I've never had a good luck with masking tape + Vallejo.  Even days after spraying Vallejo, masking tape lifted it.  

I use AK Interactive acrylic primer or Tamiya primer and they bite plastic extremely well.   I sometimes don't use a primer and spray Tamiya acrylics directly onto plastic.  I've never had a lifting problem with Tamiya with or without a primer.

How long after you paint are you masking.