General Technique question on base paint color adhesion

Carnet

Carnet

Well-Known Member
I've been having some recurring issues on my last couple of projects with the base paint layer peeling off of the primer with my masks in random spots. My main focus is Star Wars models, and usually I can work it out as convenient paint chipping/weathering effect, but it is something I would rather have control over it happening where I want it to as opposed to at random and unexpected (wrong) points on the model. It's especially disheartening when it happens after your 3rd or 4th weathering filter, it's hard to fix that.

I typically use Tamiya Super Fine primers and I paint with enamels...could it be that there is not enough of a "tooth" for the paint in the Super Fine Tamiya?

Another guess I had as to what was causing it might be oils from my fingers getting onto the primer causing the enamel not to stick in those spots?

I don't generally clean my models after I lay down my primer, should I be doing that?

Edit: Just to be clear, this is a problem with my paint sticking to the primer. It is not a problem with the primer sticking to the plastic or resin.
 
Last edited:
Here are some steps to help you...

1.Wash the model after ANY handling before you prime. Yes, finger oils can interfere with adhesion.
2. Apply your first layer of paint as a "tack coat". Just mist the first layer on. You don't want full coverage. This gives the next two layers of paint tooth to grip.
3. Apply your second coat of paint as a slightly wet coat, but not too heavy either. Heavier than before, though.
4. Apply your third coat full wet, but not wet enough for it to run.
5. Allow this to dry for 24/48 hours if you're using enamel paint. Enamels cure slowly.
6.Continue any masking you wish to do.

It's important not to ever touch the model with your bare hands again after it's primed. Finger oils can mess up things. I wear disposable black nitrile gloves. If you aren't allowing full time for the paint to cure, it can pull up. If you are using solvents during weathering that eat enamels, you might be making the paint weak.
 
Everything there I do...except the gloves. I’ll give that a shot.

No issues with the primer sticking to the model, the problem is the base coat sticking to the primer.
 
The only times I've ever had paint not stick to primer was when I was using two incompatible mediums.
Like enamels over an acrylic primer, or acrylics over an enamel primer.
One I think you can do, and one you can't, but I don't remember which is which because I learned my lesson years ago and now I use either all enamels or all acrylics.
I don't mix mediums.
 
Axlotl said:
The only times I've ever had paint not stick to primer was when I was using two incompatible mediums.
Like enamels over an acrylic primer, or acrylics over an enamel primer.
One I think you can do, and one you can't, but I don't remember which is which because I learned my lesson years ago and now I use either all enamels or all acrylics.
I don't mix mediums.
Click to expand...


Tamiya surface primer is Lacquer, is it not? It should be perfectly compatible with enamel.
 
Dear Carnet;
I paint my models with enamel paints and I have never had an issue like the one you are describing. I don’t wash or degrease my models prior to painting, and I only wear gloves to protect my hands from getting paint on them when I’m airbrushing....

Hear is my suggestion to you- Stick with enamel. Don’t even use the primer. Enamel is so durable that it can be used as a primer. However if you feel you need to use a primer to conceal some surface imperfections, use auto body primer. I have used this combination and it works wonderfully.
I hope this is of help to you. Regards;
SCUD
 
SCUDMAN said:
Dear Carnet;
I paint my models with enamel paints and I have never had an issue like the one you are describing. I don’t wash or degrease my models prior to painting, and I only wear gloves to protect my hands from getting paint on them when I’m airbrushing....

Hear is my suggestion to you- Stick with enamel. Don’t even use the primer. Enamel is so durable that it can be used as a primer. However if you feel you need to use a primer to conceal some surface imperfections, use auto body primer. I have used this combination and it works wonderfully.
I hope this is of help to you. Regards;
SCUD
Click to expand...

I will give it a shot, thanks!
 
If the primer is peeling off the plastic I would make sure the plastic is clean before you prime it and let it dry for at least 24 hours. If a lot of taping and masking is being done you can try Duplicolor adhesion promoter that is fist sprayed on the plastic and then the primer is sprayed over that. This will help the primer stick better to the plastic so when a lot of taping is done it won't peel the paint off. I generally use Duplicolor primer on all my models followed by either a lacquer basecoat and sometimes Tamiya acrylics with good results. If a lot of taping or masking is going to be done like the Aztecs on the 1/350 Enterprise I will spray the adhesion promoter first on the plastic followed by the primer, basecoat, Aztecs and details. Always clean your surface before you paint it, wear gloves and let it properly dry before moving on to the next step. Could be the enamel paint is interacting with the Tamiya primer either incompatible or primer is not fully dried.
 
Sorry, I wasn't clear in my first post. The problem is that the paint is peeling off of the primer. This is a paint/primer issue, not a primer/plastic issue. The primer is firmly attached to the plastic, I have never had an issue with my primer. The paint is pulling up off of the primer.
 
Thanks for clarifying.

I would make sure that you clean the primed surface before spraying the enamel over it. I usually wipe down the surface using a mixture of 75% alcohol and 25% water with a lint free blue shop towel. This will dry quickly leaving no residue and should eliminate surface contamination.

If you have been using the same primer / enamel combination in the past with no issues and only had problems on last 2 builds maybe the enamel needs to dry longer before you applyany tape/masks on it, primer surface needed to be cleaned, maybe the enamel is bad or a combination of the ones listed could be causing it.



Carnet said:
Sorry, I wasn't clear in my first post. The problem is that the paint is peeling off of the primer. This is a paint/primer issue, not a primer/plastic issue. The primer is firmly attached to the plastic, I have never had an issue with my primer. The paint is pulling up off of the primer.
Click to expand...
 
I have a few spare kits to test on before I get around to painting my next project. I'd like to see if I can make the problem happen, and then also try to stop it from happening.

Thanks for the input, everyone!
 
The reason we use primer is to prepare for the paint going onto the surface....primer offers better adhesion for the paint....you shouldn't have to do anything to make sure the paint sticks to the primer.....

....so either the primer has lost it's quality (you've said it's your regularly used stuff),....or the paint cant be used with that primer

Test the primed surface with different paint.....just to see if its the paint

I always use car primer rattle can......Hycote.....nice & fine,...never clogs,....& cheap

J
 
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