Brushed varnish problems

[Prashun Patel]

I am finishing a countertop in Waterlox (Gloss regular varnish). I wiped on a few coats (thinned with MS) and then laid on a brushed coat.

About 10 mins into the drying I noticed some tiny spots where the varnish didn't flow; I should have thinned it a little bit more. Foolishly, I took my brush (which was by then hanging in mineral spirits), brushed it dry on a rag, and then backbrushed the problem areas.

Unfortunately, this resulted in uneven leveling. There are 'sag' marks now in parts of the finish.

My goal was to use a brushed coat to fill the pores; and then to wipe on the final coats; I'm not looking for a highly built up finish.

What's the best fix for this? (My idea is to wait a week and sand with 320, then wipe on a final couple more coats)

Will a few subsequent wiped on coats of varnish hide any witness lines caused by aggressive sanding?

[Chris Fournier]

"Aggressive" and "320 grit"? I'm not entirely sure what this would look like but I'd say that you'd be touch and go if wiped coats were all that was left to complete your surface.

Rather than sand have you considered using a very sharp card scraper with a very fine burr to level your booboos? Once the varnish is hard enough which won't be long you can try to level the areas with a light touch. As you remove the surface skin you'll notice that the varnish begins to tear a bit. At this point stop for a day and let this freshly exposed layer harden a bit, once it has you can have at it again if your need to.

The right touch with the right card scraper can leave you with a surface that only needs burnishing to bring it up to the untouched finish around the affected areas.

Good luck

[Tim Sproul]

I don't know how large the countertop is. Scraping large surfaces is tedious and from my own experience it is difficult to maintain the high level of concentration required when scraping finishes. If you want to scrape the surface, Lee Valley sells very thin scrapers that work well for scraping finishes.

For a large surface, I find an electric sander is quicker and safer.

Next time you brush varnish, you might consider a brush like those sold by Joel at toolsforworkingwood.com

[Chris Fournier]

"About 10 mins into the drying I noticed some tiny spots where the varnish didn't flow;" Quote from OP.

Tim these are small defects which he has to fix, not large surfaces.

[Henry Ambrose]

Waiting a week and then sanding seems a foolproof method. You might speed this up by wet sanding with a little mineral spirits for lubrication. Kinda hard to say until we know if its a hand size area or an entire counter top.

[Prashun Patel]

There are several sags over the entire 10ftx2ft expanse of the counter. There are also a lot of dust nibs.

[Henry Ambrose]

Try a small area with mineral spirits and wet/dry paper. If it looks like its doing what you want and you have the energy, do the whole thing. I've used a big sanding block like the ones for drywall sanding - nice big handle and half a sheet at a time. I doubt it'll take that much sanding, but you do have a fairly large area.

[Dan Hahr]

As soon as the varnish is cured enough for sanding, sand the thicker areas flush with the rest and recoat. If it is still gummy, scrape it off with whatever; I use a bogus credit card when working on dyed wood so it doesn't scratch the wood. I've never had a problem with witness lines in real varnish, unlike polyurethane. Not sure what your weather is like, but I've found that a day or so is fine for sanding between coats. I think it is actually better sooner than later, as you do not want the first coat to fully cure. Just make sure the finish is creating powder when sanding, not gumming up the paper.

Hope this helps, Dan

[Prashun Patel]

I've sanded with 320. It's looking pretty good. I did get one witness line, but I'm going to hope it disappears with more coats. I'm wiping the rest on.

The problem is that the counter is already installed. It was not practical to finish it elsewhere, in a dust-free environment. When I wipe, I never have dust or missed spots.

Anyway, thanks for the input.

[George Octon]

You're just getting started anyway; three coats is nothing for a countertop anyway. It's only the last coat that counts. But it's always sand it and put on another coat. I would assume that overnight would be more than enough time between sanding, you can even for the most part sand exterior spar varnishes overnight if the weather is decent.

[Scott Holmes]

Recoating will hide the witness lines. 320 may not be coarse enough to flatten the surface. Scraper or 240 may work better. Then hit it with 320 to get rid of any 240 scratches.

3 or 4 wipe on coats is about the same build as one brush on coat. I like to wipe on 3 coats per evening about an hour or so between coats. You must wait until it's dry-to-the-touch. Waterlox takes a hour or so, other varnishes are a bit faster to dry. A wipe on coat on a 12' x 24" top should take 3 to 4 minutes, tops. Wipe it on like the kid wipes the table at the burger joint and let it dry.

You need to thin the Waterlox 50/50 with mineral spirits to make it a wipe-on.

[Prashun Patel]

Scott, thanks as always!

[Mark Levitski]

Is it also suggested to thin the Waterlox Original Sealer/Finish 50/50 if one is to wipe on?
Thanks.............Mark

[Prashun Patel]

No. The Original Sealer/FInish is formulated to be a wipe on already. It can also be brushed as is, but does not require thinning if wiping. Only the Satin and Gloss products require it, because they are full strength.

[Henry Ambrose]

I've wiped them all without thinning.
Pour it on, scrub it in and around, then pad off the excess. (sometimes wet sanding to fill the grain)
The last coat I wet the pad and wipe thin enough that the surface is an even "color" just barely wet but no sense of anything sitting on top.
Giving each coat a full day to dry will make the whole project dry faster even though you'll be putting on finish longer.