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Varnish Application problem

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Forum topic by Vindex posted 07-25-2017 02:14 AM 521 views 0 times favorited 11 replies Add to Favorites Watch
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Vindex

76 posts in 656 days


07-25-2017 02:14 AM

I am in the midst of my very first finishing project, and I ran into a problem today when I tried to apply the first layer of varnish. I have been doing test pieces before each step until now, and I got overconfident and when the varnish looked like it was evenly applied on my test pieces, I went ahead and put it on the real thing immediately before the test piece had dried.

The tabletop is black walnut. I used wonderfil grain filler to fill the pores and then used Watco Danish oil to give the wood a warmer color (I applied a washcoat of dewaxed superblond shellac to the end grain before both the filler and the danish oil to keep the wood color consistent). That part looked great.

Today, I applied a coat of the same dewaxed shellac to the whole top (padded on), waited for it to dry, and sanded the top with 320 grit. The shellac did not dry flat, and I had to sand more than I expected to make things work. There was white dust from sanding the shellac, and i brushed the top and wiped the surface with mineral spirits to remove this dust. Once the mineral spirits had evaporated, I applied a coat of Behlen’s Rockhard Tabletop Varnish (thinned 25% with mineral spirits) to the top. At first, it looked as if the application had gone well, but then I noticed it was not filling out well at all. Here is a picture of one of the dried test pieces so you can see how the table was beginning to look:

I quickly grabbed a rag, soaked it in mineral spirits, and began wiping the table to thin out the varnish and spread it out. For the most part, it worked, but I did get one area where the finish looks wrong. I don’t know if it is fish eye or something else:

I have a few questions:
1) Could I have sanded through the shellac in this area and caused this? I had read that Behlens usually goes well over danish oil, so I had hoped that the shellac coat was not too essential.
2) Why was the varnish not filling out? Is it the heat? I live in Texas, and the temperature in my insulated garage is in the low 80s no matter what time of day or night it is. If so, how do I work around this problem? Should I thin the varnish more? Is there another trick?
3) Is this something that will get resolved simply by applying more coats of varnish, or do I need to do something else before I proceed?


11 replies so far

View TungOil's profile (online now)

TungOil

743 posts in 329 days


#1 posted 07-25-2017 02:34 AM

In my experience, fisheye usually manifests itself as small (~1/16”-1/8” diameter) circles around a contaminated area. I’ve never seen them the size you are showing above so I would not think it’s fisheye. Hard to say from just images, but it looks like the finish applied unevenly.

When I wipe on finish I use a finish specifically formulated for wiping so I don’t have to bother with thinning it and I apply it with a pad of folded cheesecloth. The trick with wiping finish is to apply may thin layers and build the finish slowly. The first coats usually look uneven.

Perhaps you applied it to heavily, need to thin it a bit more, or both? keep experimenting before you go back to your finished piece.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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Vindex

76 posts in 656 days


#2 posted 07-25-2017 02:51 AM

Thanks for the quick response, TungOil. That makes me feel a bit better. I forgot to mention that I initially brushed the varnish on (I also tipped off the varnish until all the bubbles were gone). When I saw an hour later that the brushed on varnish had nickel sized “craters” forming (see my test piece above), I decided to used the mineral oil soaked rag to thin the varnish and level it out before it cured.

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TungOil

743 posts in 329 days


#3 posted 07-25-2017 03:07 AM

If the first coat went on as uneven as it looks in that first photo, I think you will need to let it dry good then sand it flat before you proceed. Best bet is to be sure you are getting the finish you want on a test piece before committing to the real thing.

Edit: are you sure the shellac was de waxed? Any chance there was some kind of contamination like silicone, wax, WD-40….?

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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Loren

9609 posts in 3482 days


#4 posted 07-25-2017 03:10 AM

I haven’t used that varnish but when I
do use varnish I have seldom thinned
it. Instead, I dip the bristles in spirits prior
to beginning. This seems to help prevent
the bristles from loading excessively near
the brush ferule.

I am hardly an expert on varnishing but
from what I do know your problems may
come from over-thinning and over-brushing.
It can be hard to trust a varnish to level-out
on its own but that is exactly what they
are formulated to do.

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Vindex

76 posts in 656 days


#5 posted 07-25-2017 03:11 AM

Luckily, the first coat went on much better than the first photo. The first photo is a test piece that I did not try to save. The first coat on the real thing looks decent. It’s just the area in the bottom two photos (those are pictures of the same area from different angles) that looks off.

I had planned to brush on the varnish, but given my problems with brushing, I am contemplating wiping on thinner coats. Is that a bad idea if it is not formulated for wiping?

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Loren

9609 posts in 3482 days


#6 posted 07-25-2017 03:14 AM

If wiping, varnish can be thinned. I’ve found
wiping thinned varnishes easier than brushing
but it requires more coats.

View Lazyman's profile

Lazyman

1499 posts in 1222 days


#7 posted 07-25-2017 12:16 PM

Are you sure that mineral spirits was the correct solvent to use to thin the Behlen’s Rockhard Tabletop Varnish? Behlens sells a a special thinner (rockhard reducer) for this finish so perhaps the mineral spirits caused finish to break down or something?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Fred Hargis's profile

Fred Hargis

4756 posts in 2328 days


#8 posted 07-25-2017 03:51 PM

Well, having never used the Behlen’s product I looked it up. It’s a urethane varnish with a very high resin content, so I have to think thinning it a little makes it go on easier. In looking at the MSDS for the reducer I can’t tell if it’s different than standard MS, but can’t imagine it’s new invention. My conclusion is that you should be able to thin the Behlens to a wiping consistency and use it if you want to. I would also think normal MS would be just fine, just be sure to skip any of the “green” stuff. But back to what shows in your pic, that looks like a missed area and it’s possible you sanded through the shellac at the spot. If you did sand through, you may have removed the color enhancement from the Watco, and that’s causing the appearance. But now you’ve sealed it with the Behlen’s so I’m not sure if you can get back to where you can blend it in. I think I would try to recreate the problem on your scrap, then sand it down and see if adding a little BLO will get the color back, then recoat with the varnish. I don’t think just more coats of Behlen will solve the problem, though it may get less noticeable as the finish builds.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Vindex

76 posts in 656 days


#9 posted 07-25-2017 11:43 PM

Thanks so much to everybody for the help. I managed to solve the problem today. It turns out that I needed to stir the varnish more thoroughly. Once I did that, I managed to get an even application when the varnish was brushed on a test piece. Nevertheless, the brushed on varnish took so long to dry, that it accumulated far too much dust for my taste. I have applied two wiped coats of the varnish using the method described here:

http://www.askhlm.com/Articles/ArticleViewPage/tabid/75/ArticleId/5/Wipe-on-Varnish.aspx

so far, it has gone on very well, and the uneven spots have blended almost completely.

Regarding the solvent, the Q&A section on the Rockler website says that Behlens reformulated the Rockhard varnish so that it can now be thinned with MS.

I guess, “Did you stir the finish thoroughly?” must be the finishing advice equivalent of, “Is the device plugged in?” I feel like a bit of a fool now.

Thanks again!

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TungOil

743 posts in 329 days


#10 posted 07-26-2017 01:16 AM

glad you figured it out.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View Fred Hargis's profile

Fred Hargis

4756 posts in 2328 days


#11 posted 07-26-2017 12:22 PM

Ditto, good to see it resolved.

-- Our village hasn't lost it's idiot, he was elected to congress.

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