discussion Varnish Issue

[Bortig the Viking]

Can anyone tell me what's wrong, I sprayed a couple of coats of semi gloss black Zero paint then a coat of Zero clear and it came out like, the only description I can think of is a crackle effect, like texture. Although it's not what I wanted it actually looks quite good for my locomotive, like rough iron.

 

[AlanG]

Was the paint totally cured before you varnished it?

 

[Bortig the Viking]

I left it for a couple of days, my wife came up with another description, flocking.

 

[Tim Marlow]

Sounds like what Alan said....where did you leave it to dry? Just thinking that if you left it in an unseated area like a garage it may not have actually dried in that period.....

 

[Bortig the Viking]

It was inside the house in my man cave, as my wife keeps telling me it's 21 degrees C in there, that should be enough or should I wait longer, how do you know when's it's cured fully?

 

[AlanG]

Or as i have found with Humbrol enamel paints, if they are not stirred/mixed well enough then they take forever and a day to dry.

 

[Bortig the Viking]

Or as i have found with Humbrol enamel paints, if they are not stirred/mixed well enough then they take forever and a day to dry.

How longs that?

 

[Tim Marlow]

That should be plenty....Zero are lacquers aren’t they? Only other thing I can think of is that the varnish layer was a bit thick and the surface skinned over before the underlayer dried out...
Paintguy might be our SME here.....

 

[AlanG]

With some of the humbrol paints i had this happen on, it was about 3 days before it didn't feel tacky.

 

[Tim Marlow]

Just out of interest, what were you spraying? Only asking because some resins don’t like solvent based paint....

 

[Bortig the Viking]

That should be plenty....Zero are lacquers aren’t they? Only other thing I can think of is that the varnish layer was a bit thick and the surface skinned over before the underlayer dried out...
Paintguy might be our SME here.....

So maybe I applied it a bit heavy then, got more to do so will try it again but with very light coats, to my eyes it's hard to tell when it's covered.

 

[Guest]

Only other thing I can think of is that the varnish layer was a bit thick and the surface skinned over before the underlayer dried out...

Without seeing it, this is one very likely cause. There's a technical name for it that I can never remember, but the Yanks call it "mud drying" which describes it well. Imagine a dried river bed where the soil is still damp underneath but the surface is bone dry. The top layer shrinks and hardens due to the moisture loss but the underside doesn't, causing cracks or fissures. Too much paint/clear/whatever in one go can cause this just as Tim describes.

The other possibility is that the solvents in the lacquer/varnish, if applied heavily, can "soak into" the paint underneath. This reactivates and expands it as the paint absorbs the solvent, often causing it to "pucker up" a bit like crocodile skin.

Pictures would help, but I think you may have gone a bit too much too soon.

 

[Bortig the Viking]

Without seeing it, this is one very likely cause. There's a technical name for it that I can never remember, but the Yanks call it "mud drying" which describes it well. Imagine a dried river bed where the soil is still damp underneath but the surface is bone dry. The top layer shrinks and hardens due to the moisture loss but the underside doesn't, causing cracks or fissures. Too much paint/clear/whatever in one go can cause this just as Tim describes.

The other possibility is that the solvents in the lacquer/varnish, if applied heavily, can "soak into" the paint underneath. This reactivates and expands it as the paint absorbs the solvent, often causing it to "pucker up" a bit like crocodile skin.

Pictures would help, but I think you may have gone a bit too much too soon.

I think you've nailed it, think I applied too much too quickly, oh well you learn.