color coat problem

[mnwildpunk]

So on my latest project I painted it like I always do but this time the color coat is not sticking after two weeks it flakes off. The primer is on it like a rock so idk why I'm having issues. Btw it is m.m. One coat laquer

[Mike Kucaba]

I can only think of two things Bad paint, or something with the primer.

[jwrass]

Dave,

Did you sand or scuff the primer before color coat?

[MeatMan]

Then wash it!!

[mnwildpunk]

Jwrass yes I sanded it as usual with 600 grit

[jwrass]

Dave, You may or may not be able to save it. Like Mike said you simply may have some bad product which is a bummer and makes one doubt them self because we all assume that what we buy should not be defective so in our minds we rule out the product when in fact it happens, it has happened to me more than once and I'm sure it will happen again before I retire my spray equipment.

I'm going to assume some things like you have experience painting, you know how to prep your sub straight, solvent flash times, proper prep procedures between coats of primer and color coats. Cleanliness between coats, using a tack cloth between coats. If not I will gladly back the train back into the station and start at 101.

Let's try to trouble shoot this problem! First we need to ask some questions......

1) How did you prepare your surface, from the beginning ? (washing, sanding, etc before you applied primer)

2) What type and brand of primer did you use?

3) How did you prepare the primer before your topcoat ? ( sand paper grit, cleaning before top coat)

4) What type and brand of topcoat did you use?

I know you said you used 600 grit sandpaper before the topcoat so lets keep that in mind. You said the top coat is flaking off, is it all coming off or just in spots? the flakes that come off are they brittle or do they still have some flex in them?

Lets start with that and see what we can determine. jwrass

[vypurr59]

Dave, You may or may not be able to save it. Like Mike said you simply may have some bad product which is a bummer and makes one doubt them self because we all assume that what we buy should not be defective so in our minds we rule out the product when in fact it happens, it has happened to me more than once and I'm sure it will happen again before I retire my spray equipment.

I'm going to assume some things like you have experience painting, you know how to prep your sub straight, solvent flash times, proper prep procedures between coats of primer and color coats. Cleanliness between coats, using a tack cloth between coats. If not I will gladly back the train back into the station and start at 101.

Let's try to trouble shoot this problem! First we need to ask some questions......

1) How did you prepare your surface, from the beginning ? (washing, sanding, etc before you applied primer)

2) What type and brand of primer did you use?

3) How did you prepare the primer before your topcoat ? ( sand paper grit, cleaning before top coat)

4) What type and brand of topcoat did you use?

I know you said you used 600 grit sandpaper before the topcoat so lets keep that in mind. You said the top coat is flaking off, is it all coming off or just in spots? the flakes that come off are they brittle or do they still have some flex in them?

Lets start with that and see what we can determine. jwrass

This is some very helpful info, thanks jwrass

[Art Anderson]

A few questions, if I may:

1) Was the primer used a different brand (or type) than the Modelmaster 1-coat? If so, then it probably wasn't the surface preparation of the plastic, since you say the "primer is on it like a rock". Keep in mind that all lacquers, even those sold by both Testors and Tamiya, do have at least some "penetrating" solvents in them, as that is needed, to not only give adhesion to the plastic model surface, and to allow succeeding coats (primer or color coats) to adhere solidly to the substrate (previous layers of lacquer or other type of primer/paint used). If you used, say, a kind/type/brand of primer sold for either general household or automotive use, more than likely the Modelmast One-Coat solvents could not penetrate that sufficiently (if at all) for a truly positive bond.

2), Did your color coat just flake off "gratuitously", that is without some other physical act on your part? By this I mean, did the paint flake away by merely touching it, or did you mask off the color in order to add another color over it (thinking 2-tone paint scheme here), and then the masking tape pulled it, causing it to chip and/or flake away? If the latter, that could also be a simple matter of either the type of tape used for masking, or even technique. Using a lower-tack (less stickum power) tape can minimize peeling off the original color coat, as some masking tapes are rather "high-tack" meaning they can really grip a painted surface. Also, technique can help a lot here: Many people tend to pull masking tape straight up (at least nearly a 90-degree angle to the painted surface)--this alone can ruin an otherwise great paint job, as such an angle puts LOTS of stress on the bond between layers of paint, even paint on the plastic itself. Rather, learn to pull masking tape off a paint job back--AGAINST itself, as this lets the tape "roll away" from the painted surface, which does greatly minimize the possibility of pulling the color coat off the primer, even if the primer is not the same brand/type of lacquer used. (Been there, done that a lot, frankly).

Ordinarily, surface "contamination" shows up very quickly when spraying any paint, most often as "fisheyes", where the liquid paint sprayed on literally seems to "run away" from a little spot or speck, but not always, and certainly this is less a problem with a spray can than it is with the far finer spray from an airbrush--but contamination of the primer's surface can also be an issue. Skin oils on one's fingers, even vapors from fixing a meal on the stove can settle on a surface to be painted. The solution is to remove that (even if you don't seem to see anything) before each succeeding coat by washing with soap and water before each successive coat of paint (be careful about dishwashing detergents, as many of those contain silicones, for that "cleaned down to the shine" but which can play absolute hob with paint adhesion) along with frequent hand-washing with soap and water, unless you are using say, the nitrile exam gloves sold in most pharmacies (those blue or purple gloves used by EMT's, etc.) and your model room is well away from the kitchen.

These are some points to take a look at.

Art