varnish on top of gloss paint?

[batbeanz]

hi.
i have painted a piece of furniture with gloss black paint, the finish is quite good and smooth.
what type of varnish can i put on to to create a tough finish resistant to chips and scratches?
thanks

 

[Scrit]

Hi

When you say gloss black paint, do you mean an acrylic gloss or an oil-based gloss? I'm trying to figure out what the finish is so I can work out what might be compatible. I've stripped varnish over gloss paint before and it looks a bit like a toffee apple as the varnish yellows and crazes with age.

Scrit

 

[batbeanz]

its a black oil based gloss so should i use a oil based varnish?
cheers

 

[Scrit]

Yes, maybe, but the problem is that oil based paints tend to "cure" to final hardness quite slowly, so any varnish you put on top may just craze after a couple of years. You'll also have a problem of adhesion. The original finish is smooth and presents little for the clear coat to bond onto. That can result, eventually, in the delamination of the protective clear coat - it will simply peel away over time. This is something you see from time to time on woodwork in old houses.

I think you'd be better off leaving the black paint as is and consider refinishing in a more durable finish if or when you start to see signs of wear.

Scrit

 

[batbeanz]

should i use an oil based varnish?
i was thinking would it be best to give the gloss paint a sanding down with fine sandpaper or wire wool before i apply the varnish.

 

[colin taylor]

When refinishing posh kitchens using THAT brand of posh paint, which looks nice but shows up every mark, I often recommend a coat of eggshell acrylic varnish. This improves the scuff-resistance of the surface. I use Craig & Rose which whilst a bit pricey is good stuff.
Two things are important. Water-based coatings don't like uncured oil, so I always leave a minimum of a week before varnishing (for a gloss, which contains more oil, maybe longer). The other thing is that water-based coatings generally like to have a mechanical bond, so rubbing down the surface is essential.
You could use an oil based varnish, but again rubbing down first. It will yellow over time but that shouldn't matter over black. I think you would need a "long" oil varnish rather than a "short" resin type varnish, then it would remain flexible over the gloss. I think "yacht" varnish is "long".

 

[batbeanz]

thanks for that.
i think i will wait about 2 weeks before varnishing, do you think a yacht varnish will be best then? what grade sandpaper or wire wool should i use to avoid rubbing down too much.
cheers

 

[colin taylor]

220, don't ever use wire wool, any stray bits left in the finish will stain.