How to Deal With Lacquer Burn?

[Skip]

I picked up a couple of models off of eBay and at Garage Sales only to discover lacquer burn after stripping. In most cases the original builder's fix was to lay the paint over the burned plastic really thick, not a very good fix.

How do you go about repairing lacquer burn? Obviously the first steps would be strip then sand out the burn... In the past when I've had this issue it bled back through the paint after strip and sand. Anyone successfully repaired this issue?

[Snake45]

I'm not sure what you mean by "lacquer burn." Can you describe the condition a little?

I'd think that sanding and priming should give you a good base for paint. But maybe I'm not understanding the problem.

[StevenGuthmiller]

What I'm assuming you're talking about Skip, is what most of us would probably refer to as "Crazing". When the plastic "wrinkles" up from the paint being too "hot". Usually occurs from applying lacquer paints directly over un-primed or insufficiently primed plastic. As far as I know, the only remedy would be sanding. The damage is in the plastic itself. so in order for it to be repaired, you must remove a layer of plastic. As far as bleed through, I would think that as long as you sufficiently prime after sanding, there sould not be an issue. Several coats of a good primer may be necessary. Steve

Edited September 15, 2014 by StevenGuthmiller

[Cato]

Sand as well as you can. Apply a skim coat of filler. Then a coat of Future.

Prime and finish in the usual manner.

[Krazy Rick]

How badly is it crazed ? ...... is the plastic soft ? If it is soft after you remove the paint, I would let it air dry probably at least a week, before sanding, if there is no softness, or paint smell to the plastic; I would assume that it would be fine to sand & prime.

[Guest]

I have a '61 Falcon with the same issue. Most of the burn has sanded out successfully so far using 220 grit. By the time I sand it again with 320, then 400, there should be very little burn left. Whatever is left will be skimmed with putty,sanded and then primered. Like Cato mentioned, I'll brush a coat of future over it, then primer.

[jwrass]

Skip,

Their are many ways to combat crazing problems. And many of the responces have merit and could work. What you have (if it's crazing) is a common mistake many new painters make be it A model kit or 1:1. All petroleum bases solvents are corrosive to certain types of materials some use the terminology as hot which would be a proper definition, i.e. Lacquer thinner is hotter than Mineral sprits, consequently minerals spirits would be less aggressive or corrosive to the plastic. My guess it that the original builder started the painting process and the solvents started to craze the surface (this can happen with primer or paint, solvents don't discriminate) crazing it merely the first phase of melting the plastic. My guess it the painter started to see the crazing and figured well I'll just put the material on thicker and wetter which will only makes the problem worse as the solvents don't flash and the material stays wet to longer which give the solvents more time to attack the plastic.

There is no guarantee my process will work, this is how I would proceed.

1) Sand the surface with 180-220 grit paper and try to feather out the bad spots the best you can.

2) Apply a skim coat of a 2 part glazing putty such as Evercoat 100408.

3) Sand and feather skim coat and finish to a 400-600 grit paper and a red scuff pad in preparation for primer.

4) This is optional but I would spray two lite coats of Polpropylene clear plastic primer with recommended flash times between coats. The reason I say this is optional is this product is expensive. I have to have this product for some of the 1:1 custom paint work I do so it's always on hand in my mixing booth. This product acts as a adhesion promoter and sealer and it made specifically for plastic.

5) If you choose to do step 4 or choose not to do that step apply your primer in very lite coats with recommend flash times between coats, watch the surface as you apply the primer, you may still get a few hints of crazing, if so apply the next coat at bit dryer and proceed with the next steps (if the surface continues to craze you may not be able to save it) of applying more coats of primer. Better to apply 10 dryer coats than 5 medium coats. after your first round of the priming process let the surface dry for a few days and block sand with wet or dry 400-600 grit sand paper to remove any imperfections or sand scratches continue to do the prime and sand process until you feel the surface is ready for final sanding in preparation for your color coat.

*** The theory of the lite coats is to get the solvents to flash as soon as possible so they don't have time to attack the plastic. As the film thickness of the primer builds it will start to form a barrier between the plastic and the primer which should eliminate any further crazing, the key is to have the solvents flash before they reach the plastic to prevent crazing.

6) If you feel your surface is ready for paint from your prime and sand sessions wet sand the surface with 600-800 grit paper followed by a grey scuff pad and prep for paint.

7) Apply your first coats of paint on the med dry side (allow recommended flash times) to make sure you are not having any reactions in the primer, if the surface looks fine and you are not getting any print back from the original problems you can start to apply the coats wetter until you have the coverage and color you were looking for.

I personally would not use future as a sealer as it contains water and other ingredients that may not be compatible with solvent based products. It has been my experience that water and solvents don't play well together unless the product has a dehydration component in their formula like waterborne OEM paints which are compatible with solvent based clears.

Others may have used future and have had success with that process, that is a choice only you can make.

Having being a 1:1 custom painter for some 35+ years (see my profile) I always use one product line from start to finish, I never mix brands. All of the paint work I do is high end work and I can't afford to take chances with failures as that can cost me many $$$$$$$$. I don't feel that extreme process is necessary for modeling, however I feel best practices should always try to be applied.

I hope this helps, Good luck! Cheers, jwrass

[Ace-Garageguy]

So far, I've been able to kill all of my crazing issues (even a really bad mess I made, stripping lacquer from late-model, soft Revell styrene with REAL paint stripper...which attacked the plastic much like having poured liquid cement on it) by repeatedly and gingerly priming, allowing to flash COMPLETELY so as not to trap solvents, sanding flat, and primer-sand-primer-sand, repeat as necessary.

I'm sure you regulars are sick of seeing this car over and over and over, but the truth is that this is the decklid I thought I'd ruined (using WAY TOO HOT self-etching primer) and stripped with the real stripper, then saved with the above technique. Looks just like this, still, two+ years later, and nothing has ghosted through.