Zinsser Cover Stain is Zinsser’s oil-based primer and sealer. It is suitable for a huge range of surfaces. But, you are here because you want to know whether it can be used on top of varnish? Well, there is only one way to know for sure, and that’s to test it. So I grabbed a tin of cover stain, varnished some wood and got some testing done. let’s have a look at the results.
Can You Use Zinsser Cover Stain Over Varnish?
Yes, you can. My own testing showed that Cover Stain worked well over varnish. It painted onto the varnish really well and more importantly, it adhered to the varnish exceptionally well.
This is in contrast to what Zinsser themselves say, but it is what I found in my testing. You can see Zinsser’s official recommendations in the graphic below.
So to test this out and come to the conclusions I stated earlier I did a little testing. i got a piece of pine, varnished it with a clear varnish. Then painted over the varnish with all three of the Zinsser primers.
The Zinsser Cover Stain painted onto the varnish really easily. It was like painting any other surface.
It also covered the wood really well, including completely hiding the large knot right in the middle of the piece.
You can see that the cover stain has covered the wood better than the Bulls Eye to the left and probably the same as the B-I-N to the right.
After painting, I left the samples for around a week in order to give them plenty of time to cure fully. Then once fully cured it is onto the next stage of testing.
The Scratch Test
Now comes time for the real test. The problem with painting over varnish with any paint is always adhesion. because varnish is such a glossy surface it can be really hard for paint to stick to it.
So without further ado let’s see how well the Cover Stain has adhered to the varnished wood. For this, I used a piece of rough-cut c16 timber.
I like to use this method as I feel it is a thorough test for the paint while not being overkill. I don’t want to use something too soft which is not representative of the challenges the paint will face and I also don’t want to use something too hard. If I used a really hard material it would just scratch every paint and not give me any usable results.
So below is an image of the Cover Stain after the scratch test.
You can clearly see that the cover stain has worked very, very well. No scratching, scraping or any marks at all.
This is what gives me the confidence to say that you definitely can use Zinsser Cover Stain over varnish.