Do not apply in direct sunlight

[Avocet]

Well, I'm so used to not having any "direct sunlight" that I completely forgot and slapped a second coat of varnish on some wood in "direct sunlight"! (Ronseal exterior). What sorts of awful things can I expect to happen? (Looks alright so far and is drying very rapidly because it's also quite windy today).

 

[TQA]

Brushmarks?

 

[nathanglasgow]

I got lots of small bubbles in the varnish last time the sun came out when it was drying.

 

[alahol2]

I got lots of small bubbles in the varnish last time the sun came out when it was drying.

Not bubbles as such but entrapped rays of sunlight. The entrapped rays will continue to reflect around the inside of the 'bubble' in (near) perpetuity. At each reflection they will cause a slight 'etching' effect on the varnish and thus the 'bubble' will gradually get bigger. 'Bubbles' near the surface will eventually break out and allow the trapped light to escape.

 

[LittleSister]

What sorts of awful things can I expect to happen?

You'll get that deep, rich gloss only normally seen on expensive Italian wooden speedboats (that's how they get it), and be painfully dazzled whenever you're on your boat.

 

[Resolution]

Not bubbles as such but entrapped rays of sunlight. The entrapped rays will continue to reflect around the inside of the 'bubble' in (near) perpetuity. At each reflection they will cause a slight 'etching' effect on the varnish and thus the 'bubble' will gradually get bigger. 'Bubbles' near the surface will eventually break out and allow the trapped light to escape.

This is why one should for perfection do your exterior varnishing in midsummer at night, lit only by a full moon. The moonbeams lend a lustre to the varnish which is quite incomparable.

Of course there are other things best done under a full moon in midsummer........

 

[Avocet]

Thanks all. I shall look forward to enjoying my (all too rare!) bit of captured Cumbrian sunshine over the rest of the season when it's tipping it down! Well, it's pretty dry now. As has been said, the only thing I can notice (and it's very slight) is that the varnish hasn't "flowed" as well as it otherwise might - presumably as a result fo drying so quickly. I can live with it though. I just had nightmares of the UV resistant compounds in it being vulnerable to UV attack until the solvent had evaporated out or something daft like that!

 

[Twister_Ken]

I just had nightmares of the UV resistant compounds in it being vulnerable to UV attack until the solvent had evaporated out

Well, yes, that as well of course. And all that UV trapped in the varnish will go on discolouring the timber for decades to come!

 

[PabloPicasso]

Well, I'm so used to not having any "direct sunlight" that I completely forgot and slapped a second coat of varnish on some wood in "direct sunlight"! (Ronseal exterior). What sorts of awful things can I expect to happen? (Looks alright so far and is drying very rapidly because it's also quite windy today).

There'll be an exceptionally caustic reaction within the varnish compounds that will attack the substrate, trapping acidified water, causing the varnish to peel, and leaving the coated surface pitted and rotting, and compromising the structural strength of the timber.

Next question...

 

[Avocet]

Regular little rays of sunshine, the lot of you! (If you'll excuse the pun...).

 

[chewi]

Not bubbles as such but entrapped rays of sunlight. The entrapped rays will continue to reflect around the inside of the 'bubble' in (near) perpetuity. At each reflection they will cause a slight 'etching' effect on the varnish and thus the 'bubble' will gradually get bigger. 'Bubbles' near the surface will eventually break out and allow the trapped light to escape.

Don't forget to point your solar panels at it overnight to get 24hr charging...