Question about varnish: What causes this?

[TJ.]

Varnishing sucks! (I hate it) There... Got that outa the way.

I'm in the process of using up my last (ever!) can of DEFT Clear Wood Finish Semi-Gloss spray on lacquer. The main reasons being: it is the most highly toxic brain-killing substance this side of meth... it is no longer available anywhere except on-line... (apparently banned in several states???) and... it produces a result that looks like the surface of the Moon! The first layer sprayed on is fine. I use it as a first coat to stabilize a stained surface, then switch over to a brush on lacquer. Also... the very last coat usually turns out nice and smooth, but after the 3rd or 4th coat, it gets all lumpy. Anyone else have to deal with this phenomenon? And what causes it??

114304

[sunburst]

So it's lacquer, not varnish?
Looks like fish eye. Some sort of contaminant on the surface, usually silicone, that repels the lacquer is what usually causes fish eye. Adding fish eye eliminator to the lacquer is the only known cure (at least, known to me) if it is fish eye.

[Johnno]

John you are spot on, rejection- contamination. Normally you will never see it in the first coat because the contaminant is accepted by the coating and brought up by the solvents. Second coat,wham, fish eyes or lensing. Similar to trying to mix oil and water they separate. Wipe over the coating with detergent and water to remove the contaminant on the surface, dry thoroughly, cut back using new product so you don,t transfer the contaminant and prior to coating add silicone drops or anti rejection product at the manufacturers recommended rate. Over dosing will possibly cause more rejection. Good luck.
Cheers
Johnno

[Dale Ludewig]

Yep, contamination and my guess is also that it's fisheye. Wax contamination doesn't look like that. It's silicone and where it came from can be many sources. Deft is lacquer, not varnish. As stated, the solution is to add silicone to the lacquer. But you can't do that with Deft in an aerosol can. You could spray over this problem with shellac, which doesn't usually react to the silicone contamination. And then level sand. And then go back to lacquer. But it's likely to take quite a number of coats of shellac.

Another possible solution, but not likely when using aerosol sprays because you have less control than when you're using a spray gun, is to mist over the problem with lacquer so lightly that it never flows out. Build up coats that way and level sand, then hit it again with wet coats and hope it doesn't melt everything enough that the silicone finds its way back up.

Otherwise, you may find that going back all the way down to bare wood is the only solution and then it would be best to seal with shellac before starting to apply any lacquer.