Varnish on Undercoat - Yes or No ?

[Ed21]

Hi All,  

I've got a fair few wooden exterior painted garage/shed doors that have been adapted to fit with repairs 
additions and have been fully prepped with solvent primer & solvent Crown grey undercoat. The actual finshed
colour looks pretty good as is.

I've got a 5lt tin of Sadolin Exterior UV barrier Varnish going spare, so any reason why I should'nt just use this on
top of the undercoat instead of buying a gloss topcoat ?

Ed 

[JohnMo]

1 hour ago, Ed21 said:

Hi All,  

I've got a fair few wooden exterior painted garage/shed doors that have been adapted to fit with repairs 
additions and have been fully prepped with solvent primer & solvent Crown grey undercoat. The actual finshed
colour looks pretty good as is.

I've got a 5lt tin of Sadolin Exterior UV barrier Varnish going spare, so any reason why I should'nt just use this on
top of the undercoat instead of buying a gloss topcoat ?

Ed 

No reason not to, as long as you don't get a reaction from the two. 

[Alan Ambrose]

Maybe try out a little bit to check it doesn’t look horrible?

[Ed21]

3 hours ago, Alan Ambrose said:

Maybe try out a little bit to check it doesn’t look horrible?

Yes I'll be doing a test piece and the product is all good branded stuff and solvent based, .

 

I was more concenrtned about longevity and potential hassle when or if it needs a recoat later on. 

[Alan Ambrose]

Well as far as I can see they're both (as it happens): Resin: Alkyd. Solvent: Dearomatised White Spirit.

 

So maybe ... otherwise you're doing a chemistry experiment.

[sharpener]

I think if the appearance is going to be acceptable you will be OK, particularly if they are both based on the same resin polymers. Most of the covering power in a paint system is in the undercoat, it needs UV protection though which the varnish will provide.

 

We had a continual problem with a damp stain bleeding through on a chimney breast. International Paints'(*) Stain Block was completely useless but two coats of Ronseal matt polyurethane fixed it and would take matt emulsion on top.

 

* makers of the famed International Yacht Varnish which says on the tin "not suitable for exterior use".

 

 

[johncraig8229]

I would've said not to bother, but yeh as one of the previous comments says give is a test before using it if you decide to