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I have been working on a birch butcher block desk. I stained the desk then waited 24 hours before applying my first coat of brush-on satin polyurethane. I applied two coats of brush-on poly (24 hours between coats with a light sanding), but noticed brush strokes and bubbles in both coats.

I then added three coats of wipe-on satin polyurethane with a white cotton t-shirt (24 hours between coats with a light sanding; can shaken before use). However, each time the wipe-on poly dried, I noticed streaks in the finish.

To test, I added another coat to the bottom of the desk, this time thinning my wipe-on polyurethane with some mineral spirits. However, I have the same effect.

Are there any suggestions for fixing these streaks? I've considered (a) sanding then buffing/polishing (b) trying brush-on poly again (c) trying a spray polyurethane from a can and (d) applying another coat of wipe-on poly but wiping off the excess before it dries. Any help is appreciated!

Streaks in wipe-on polyurethane

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  • Hi, one detail missing I think: what finish is your wiping poly? If it is also satin I think this is your problem. You must shake the can or stir very well. Also why do you sand between coats of wiping poly?!
    – Volfram K
    Mar 24 at 6:23
  • The wipe-on is satin finish and the can was shaken each time. Also, I must've read to sand someplace as this is all new to me. It was a super light sanding each time with 320 -- just to knock some of the dust nibs off.
    – MrPeanut
    Mar 24 at 10:29
  • Hi, welcome to Woodworking. First off congrats on that varnish build you've achieved, that's very good. I'm sure this doesn't help make the varied sheen you're getting so frustrating for you. It's hard to be sure but the first suspicion in this sort of case would be the incomplete mixing of the matting agent in the varnish, so you're getting variations in sheen due to more here, less there. That you got the same effect on the test on the underside seems to point to this too, but that's not definitive since that's just one coat onto bare wood (which will always give a varied finish). [contd]
    – Graphus
    Mar 24 at 16:24
  • It's possibly not relevant but you haven't said exactly how you applied the wipe-on. There's a lot of variation in this and almost no wrong way, first you can apply it not by wiping but by spraying, by brush, roller or paint pad; then after that you can choose to remove no excess, some or most/all. All three are valid methods depending on drying conditions and personal preference.
    – Graphus
    Mar 24 at 16:40
  • Thanks, Graphus. The bottom did have one coat of brush-on poly before I tested the wipe-on. I applied poly to the top by wiping it with a white cotton t-shirt then letting it dry without removing any excess. I think I will try wiping on then removing some excess to see how it turns out.
    – MrPeanut
    Mar 24 at 18:34

1 Answer 1

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The title is really two separate queries in one that, while linked, can be treated separately.

How can I avoid streaks with wipe-on polyurethane?

With any varnish of reduced sheen, i.e. not high gloss, the main recommendation is to ensure thorough mixing. The matting agent (often very fine silica particles) invariably settles to the bottom of the container and very thorough mixing — can't stress this enough — or shaking is needed to ensure it is distributed evenly through the liquid.

Note: normally you are specifically advised not to shake varnishes and various waterbased clear finishes but wiping varnish is an exception since the application method means no bubbles can survive in the applied coating1.

You may be able to fix this with a further application of the wiping varnish as you've indicated in the Comments you're going to try, but failing that all is not lost and that's covered in the other part of the title.

How can I fix streaks with wipe-on polyurethane?

Although this can be a little trickier with satin and matt varnishes than gloss, you can generally alter (and simultaneously even up) the sheen of varnishes by rubbing down in various ways, after they have had sufficient time to harden.

This isn't something you can expect to do the day after the final coat went on, possibly not even the end of the week. The people who do this professionally tend to err on the side of caution and wait 10 days to a couple of weeks, and sometimes longer2.

Rubbing down (abrasion)
The general process to lower the sheen is to introduce scratches in a controlled way. These days this is most often done by rubbing with steel wool, Scotch-Brite or similar, or by very fine sanding. Traditionally this was often done using ground pumice or 'rottenstone' (very finely ground limestone) which are still available today if you ever want to experiment with them.

This process can be done wet as often advised in books, with soapy water or 'light oil' (these days it's common to use mineral spirits, WD-40 or a light mineral oil), in the case of steel wool in particular lubricated with paste wax, or completely dry. Doing it wet you can imagine the importance of working on a well-hardened varnish to avoid issues.

I'm personally a fan of steel wool for this purpose although some consider it obsolete, and generally recommend Scotch-Brite/an equivalent. While I don't think they work as similarly as some claim there's no denying that the results can be impossible to tell apart, and since results are all that matter pick whichever appeals to you the most. If using steel wool I would recommend 0000 (four-ought). If using Scotch-Brite the white, although grey might work OK with a light touch.

If you want to try it with abrasive paper use nothing coarser than 400 grit (~P600), and you might want to finish with 600 (roughly P1000).

There's more to any version of this process than can easily be described here so I advise a little further research if you've never done anything like it before.

Wax
You do not need to wax afterwards; varnishes in good condition do not need to be waxed. However, you can also try this as a means to further unify the surface finish if whatever you tried from the above didn't give quite the result you wanted; but as ever with wax, bear in mind this will need to be maintained for the life of the piece3.


1 Many/most being burst during application (depending on the method chosen) and more (possibly all) are burst at the wiping-off stage. Additionally the very thin nature of the varnish means that any surviving ones can easily burst on their own — one of the standard pieces of advice to reduce bubbles in brush-applied finishes is to thin slightly to increase the chance that bubbles can rise to the surface rather than being trapped in the viscous film.

2 It might be surprising but this is not necessarily because they were taught this, often it's because they learned the hard way what happens if they try to rush it :-)

3 Rewax 1-2 times a year depending on the amount of use the desk sees. Prefer paste wax over any liquid wax. If you're at all interested you can easily make your own paste wax at home, basic directions given at the bottom of this previous Answer.

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  • Thank you for the answer. I vigorously shook the wipe-on polyurethane and tried another coat on the bottom (with a white cotton t-shirt), waited 2 minutes, then wiped off the excess and let the coat dry. (This is the first time I've wiped off excess.) Unfortunately, I still have streak marks. I may try one more coat of a brush-on poly (perhaps slightly thinned). Following that, if need be, I'll try the rubbing out process with 0000 steel wool (after a lengthy curing process).
    – MrPeanut
    Mar 24 at 23:51
  • That is unfortunate! At this stage I think you should contact the manufacturer and explain the problem and see what their input is (if any.... don't expect miracles here, some companies' technical staff don't properly understand their own products, something Bob Flexner has referred to a few times). Regardless, I suggest you try just one more coat applied the same way as the last, straight onto the existing surface; see if there's any improvement. If you get exactly the same result it seems certain that something is up with that can of varnish. Which wipe-on is it by the way?
    – Graphus
    Mar 25 at 10:44
  • Oh one more thing, just wanted to mention that if you're after a fully built up finish it's advisable not to use matt or satin varnishes throughout. It's best to build coverage using gloss, then use the reduced-sheen varnish at the end for the last one or two coats. In part this because there are many fewer chances for the matting agent to cause an issue but also because you'll get much better clarity. You'll probably realise for yourself now that another option is not to use a satin or matt varnish at all, but instead to modify the gloss to taste after it has cured enough.
    – Graphus
    Mar 25 at 10:50
  • It is Minwax satin wipe-on poly. I tried one more coat and it may be slightly better, but I still see streaks where I wiped the poly. I will reach out to Minwax. I have learned about the different ways to apply poly, but that will have to be for another project. At this point, I'm waiting a month for it to cure then will try the rubbing down process.
    – MrPeanut
    Mar 27 at 17:17
  • I didn't want to say it but I was expecting (and nearly hoping) it was Minwax. Minwax are one of those companies where you can't expect much in the way of good feedback from their technical staff (Bob Flexner has specifically made a point of mentioning this a number of times over the years). But maybe whoever you get to speak to or email with might offer you a free can of finish if they accept that there's something wrong with your one.
    – Graphus
    Mar 27 at 19:27

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