novice question about base-coats/primer

gallstone

New Member
Joined
Jan 29, 2012
Messages
6
I have a question about base-coats.

I was working on a some armor and I put a base coat of black Vallejo on it. And then (after it had dried) put a couple of coats of Tamiya acrylic paint on it (out of a spray can, don't have an AB yet). Then I put on a coat of clear (I think it was umbroll) and started doing the detailing...

I had masked off and painted some parts, but when I took the masking tape off, all the layers came off right down to the plastic...
What did I miss? I read (on the Vallejo base coat can) the model needed to be degreased and I washed the sprueus before I started building, but didn't wash the assembled model. Is that something you guys would do? and if so, how?

A tried masking other bits (this model was ruined and had turned into an experiment anyway) and I put the tape on some cloth a couple of times to diminish the adhesiveness, but still all the paint came off...

Hope you can help.

Thanks!
 

sunsanvil

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Joined
Jun 2, 2010
Messages
490
Which Vallejo product did you use (ModelColor, ModelAir, Urethane Primer) and how did you apply it? You say you dont have an airbrush so I'm assuming you brush painted something. Did you thin it? If so with what? How long did you allow it to cure?

ModelAir and the Urethane primers should not be thinned. ModelColor, especially when used as a base/prime coat, should only be thinned with their thinner (water can be used for special effects, especially fine detail work, but for base/prime coats its use as a thinner can result in a weak paint film). Further, while dry to the touch almost immediately and can be re-coated in a matter of hours, full cure (and strength) doesn't happen for at least 24 hours, sometimes several days (depending on the thickness of the application, temp/humidity conditions, etc).

That aside, its a miracle your paint stuck at all: Tamiya (as far as I have ever known) does not make any acrylic spray paint. Their spray paint is a synthetic laquer. Not really a good idea to apply over top of a water based acrylic. It probably ate its way into your base coat and compromised it. You can apply acrylics over lacquer, but not lacquers over acrylics.
 

Elm City Hobbies

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May 7, 2009
Messages
3,233
You can apply acrylics over lacquer, but not lacquers over acrylics.

While that is the general rule of thumb, it isn't true.

You can put any coat over any coat, as long as the previous layer is completely cured.

I have successfully put a lacquer color coat over an acrylic primer many times with no ill effect, you just have to make sure the coat the lacquer is going over is completely cured.

Gallstone,

I assume that since you don't have an airbrush, did the Vallejo Primer come from a spray can? I know the old Vallejo primer in the big spray cans were pretty much crap. The new Urethane primers are much, much better and once cured are as hard as nails for the most part. And while they will work if you brush them on, they aren't nearly as strong as airbrushing them on.

If you aren't using an airbrush, the best canned primer is the Tamiya Fine Grey or White primers, with an airbrush, the Vallejo ones are about as good as it gets.

Just to give you an idea as to how strong they are, I primed my M51 Sherman with the Vallejo Black Urethane primer, once done and was cleaning up the airbrush, I accidentally got a drop of airbrush cleaner smack dab on the front of the tank, it probably sat there for a good 30secs before I noticed it. Fearing the worst that it would have eaten through the freshly painted primer, I reached for paper towel and expected the worse. Much to my surprise....nary even a mark where the AB cleaner sat, and this was only just a short while after spraying the primer on. Tough stuff!
 

Glorfindel

Active Member
Joined
May 2, 2011
Messages
1,501
Sounds like the curing here. On the surface the base coat of black may feel dry to the touch but the layer(and we're talking micro meters or micro something) is most likely still uncured. When you applied your clear coat over this there is no longer any gas exchange from the base coat drying. Yes, the clear coats dry pretty quick but the black closest to the plastic, literally on the plastic, is still "wet". This is why the tape lifted the paint down to the plastic. A few years ago there was a discussion about this very same occurrence at SSM and many of the mods, admin, and forum members seem to agree that this is the cause of this phenomena.
 

Chris S

Its a bit like being handcuffed to a lunatic !
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Feb 14, 2011
Messages
4,573
To be honest it simply sounds like you used a full strength masking tape ,which will lift the paint of most models.Try using low tack tape like Tamiya or painters 3M blue ;)

Chris.
 

gallstone

New Member
Joined
Jan 29, 2012
Messages
6
Thanks so much for all your advice guys.
I think the problem could well be caused by a combination factors. I did indeed use the Vajello primer out of spray-can.
This stuff:
http://www.acrylicosvallejo.com/gb/primers-gb.html
And the Tamiya spray canned paint was this stuff:
http://www.tamiyausa.com/product/item.php?product-id=85067

This is coupled with the fact that I've found myself I'm incredibly impatient when it comes to the progression of my models... so it could well be I didn't give it enough time to cure.

I didn't us Tamiya masking tape, but I did try to make it less sticky by putting it on cloth a few times... anyway I'll try the Tamiya stuff and the 3M blue. See what i like best...

Thanks again.
 

Elm City Hobbies

Active Member
Joined
May 7, 2009
Messages
3,233
Yeah, while the new Vallejo Primers in the bottles are awesome, the older primer in the cans basically sucks. Alex will probably chastise me if he read that, but its true. Nothing bad to say about their new urethane primers, nothing good to say about their old spray can ones.
 

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