lacquer cracking

[dmcspence]

Hello

I have just started using one pac lacquer from a tin for a couple of little jobs but every now and again cracks appear in the lacquer any idea what this is
I am painting on plastic if thats any use
I have had this problem once with two pac lacquer but mostly with one pac

I thought it may have been heat related maybe

regards





David

 

[TAZ]

Do you have any pics you can post.
If not, I can give you a couple ideas what it could be

 

[dmcspence]

Hello

Taz

Thanks for your reply
here are a couple of pics
the hand is approx 25mm tall to give you some idea of scale
this was my first try at lightening and a few metalic water drops thrown in for good measure
it has been done on a bike visor
i washed it rubbed it down with red scotchbrite then panel wipe dusted with plastic primer then black base coat
then lacquer cracked

again thanks for looking at this

regards





David

 

[TAZ]

My guess would be that the plastic primer is not made to put lacquer over it. Lacquer is pretty aggressive, so when you sprayed it over the plastic primer, it loosened up the plastic primer which made it 'move' under your paint. And the part that gave way was your paint which shows up as cracks.
Pretty much the same as an earthquake works, from the lower layer up.
This could have also been brought on if you put the plastic adhesion promoter too thick. You cannot put this on thick at all. Even a medium wetcoat is too thick.

 

[dmcspence]

Thanks for this Taz
I will dust it on super light in future and let you know how it goes

regards





David

 

[TAZ]

I normally put a light coat on, let it dry a couple minutes, then one more light coat.

I would still do a test panel though. Like I mentioned Lacquer is pretty aggressive.
You ought to try the newer basecoat type paints, then just clear with today's type clearcoats.

:bigokay:

 

[Maylar]

What brand and line of paint is it? I haven't seen real laquer for many years.

Real laquer is notoriously brittle. In the old days when laquer was king, we used additives called flex agents that allowed the paint to bend a bit on plastic and fiberglass substrates. I doubt any of that old technology is still available though. Even on metal panels, you have to spray laquer in very thin passes or it'll craze. As I recall, white and clear laquers were the worst offenders. Modern urethanes, enamels, and even waterbornes are far more flexible and forgiving.

 

[dmcspence]

Hello

Maylar

the paint I used was base coat by Mipa and the lacquer I used was an areosol one pac lacquer made by Indasa

 

[DavidL19]

Primer is designed to be a base so paint can go on easily. SO, I doubt that it is the primers fault. Make sure your surface you are painting on it completely smooth and completely dry before painting. Don't do anything with decals until paint is completely dry. This may help

David

 

[TAZ]

Primer is designed to be a base so paint can go on easily. SO, I doubt that it is the primers fault. Make sure your surface you are painting on it completely smooth and completely dry before painting. Don't do anything with decals until paint is completely dry. This may help

David

Keep in mind, dmspence was using a 'plastic primer' not your typical primer with catalyst. Plastic primer you just pour into the gun and spray...no hardener required.
:think1:

 

[addypaul]

Your planning is very good.I like your idea.That's a nature of the beast with lacquer. As it ages, lacquer shrinks and cracks.Usually is is worse where it was applied heavier, some of the custom paint jobs years ago were really bad because the heavy application of clearcoats.Sometimes that would melt the old finish and blend it a bit, but it was a temporary fix. In some cases it would ruin the finish, but at that point we were looking at a total repaint anyway. Wish there was an easy fix, but there isn't.