Varnishing in the tropics.

[john_morris_uk]

We’re trying to do a few odd bits of varnishing. Our chosen poison is a two pack system that’s mixed 10:1

The problem is that it’s 30C day or night. The varnish barely has time to ‘flow’ and brushing it out is impossible. Lay it on and one or two strokes before it starts going off is all you get. You have to work REALLY quickly.

The only upside is that yesterday I got three coats on (all that’s required) in an hour or so.

Would less catalyst slow things down? How critical is the 10:1 that’s specified?

 

[Black Sheep]

Pop it in the fridge an hour before mixing

 

[vyv_cox]

I have never used a two-pack varnish but for epoxy there are fast and slow hardeners, selection dependent on temperature. Is there a slow one for your varnish?

 

[john_morris_uk]

I have never used a two-pack varnish but for epoxy there are fast and slow hardeners, selection dependent on temperature. Is there a slow one for your varnish?

Not that I’m aware of.

It’s this stuff: Morrells | 450 Low Odour High Build Acid-Catalyst Lacquer

 

[john_morris_uk]

Pop it in the fridge an hour before mixing

Why didn’t I think of that? Problem is the lacquer will become the surface temperature almost immediately on application. Worth a try though. Thanks

 

[johnalison]

A little Owatrol might help.

 

[Humblebee]

Have you asked Morrells? Some paints can have retardants added to slow down hardening, perhaps there is a product which will do exactly what you want.
(Thread drift - in my quarrying days we used to add creosote to tar if it was being laid by hand. This greatly retarded the time it took to harden.)

 

[justanothersailboat]

ah! Cellulose lacquer. Not what I was thinking of when I first read "varnish".

It's meant to set super fast, you can do 3 coats in just a couple of hours even at ten degrees. It's not like varnishes. If brushing Morrells lacquer you need to thin it a bit more than if spraying. Even on a relatively cold day I found that it didn't brush out super well without the allowed extra 10% thinners by volume (though I was using 440, not 450, I think they're very close). I suspect you could add a bit more than the specified maximum of extra thinners in those temperatures. Any cellulose thinners will do if you're running out of Morrells own.

I would be more worried about humidity, the surface can go a bit sad if there is condensation, though maybe it's too hot for condensation...

 

[john_morris_uk]

ah! Cellulose lacquer. Not what I was thinking of when I first read "varnish".

It's meant to set super fast, you can do 3 coats in just a couple of hours even at ten degrees. It's not like varnishes. If brushing Morrells lacquer you need to thin it a bit more than if spraying. Even on a relatively cold day I found that it didn't brush out super well without the allowed extra 10% thinners by volume (though I was using 440, not 450, I think they're very close). I suspect you could add a bit more than the specified maximum of extra thinners in those temperatures. Any cellulose thinners will do if you're running out of Morrells own.

I would be more worried about humidity, the surface can go a bit sad if there is condensation, though maybe it's too hot for condensation...

No problem with condensation. I didn’t know about thinners. I’ll try and find some cellulose thinners as you suggest. Not always easy when you’ve mostly only got shanks pony on a Caribbean island. (I’m not looking for sympathy!!)

Thank you.

 

[justanothersailboat]

Good luck! I can imagine getting specific products must be tricky there, but I hope cellulose thinners are common/generic enough that you have a good chance. They might be being sold for use with cellulose sanding sealer rather than lacquers. No idea about the Caribbean I'm afraid, but elsewhere cellulose lacquers are becoming less common (more use of polyurethanes) but cellulose sanding sealer is still fairly available. that was what made me think to mention it.

 

[john_morris_uk]

Good luck! I can imagine getting specific products must be tricky there, but I hope cellulose thinners are common/generic enough that you have a good chance. They might be being sold for use with cellulose sanding sealer rather than lacquers. No idea about the Caribbean I'm afraid, but elsewhere cellulose lacquers are becoming less common (more use of polyurethanes) but cellulose sanding sealer is still fairly available. that was what made me think to mention it.

Is it still used in car body repair shops? That’s where I first came across it.

 

[justanothersailboat]

I don't know, but I think it's less used there now - lots of polyesters. Worth an ask though