Cleaning poly-soaked brushes

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Forum topic by Josh posted 05-25-2015 06:07 PM 716 views 0 times favorited 5 replies Add to Favorites Watch
View Josh's profile


1226 posts in 2592 days

05-25-2015 06:07 PM

Topic tags/keywords: finishing

Hi y’all!

Happy Memorial day to the Americans here and happy day to the non-Americans! I got some extra Thuja plicata from someone and decided to make an end table out of it. I stained it and just applied a coat of polyurethane to it. How does one properly and effectively clean a bristle brush to rid it of polyurethane? I’ve always just used warm/hot water and dish soap, but is there a brotherhood/sisterhood secret of the woodworking ways that I’m not aware of? As far as woodworking goes, finishing is the least of my talents.

I will wait to hear back from you gracious people.

-- Tree, wood, and box lover from Pennsylvania

5 replies so far

View bondogaposis's profile


4755 posts in 2374 days

#1 posted 05-25-2015 06:14 PM

If it is oil based poly, then mineral spirits is what you use to clean brushes.

-- Bondo Gaposis

View MrUnix's profile (online now)


6761 posts in 2221 days

#2 posted 05-25-2015 06:17 PM

If it’s normal (not water based) poly, here is what I do…

Get some mineral spirits… A dropper bottle works great for this. And get some paper towels, and rip into 2-3” strips to make it last longer.

Take your brush and hold it over a garbage can, bowl or something to catch any escaping MS. Drip some mineral spirits onto the bristles until loaded up, then use a paper towel to ‘squeegee’ them out between your fingers (thumb and forefinger). Repeat as needed.

Usually doesn’t take many rinse/squeeze cycles to get it clean, and it uses very little mineral spirits. The technique also works well for oil based enamels. I have brushes that are years old and have done hundreds of coats – and still look like they were new. I rarely ever brush poly any more though… it’s so much easier to just make my own wipe-on stuff.


-- Brad in FL - In Dog I trust... everything else is questionable

View Fred Hargis's profile

Fred Hargis

4998 posts in 2516 days

#3 posted 05-25-2015 06:27 PM

If that is oil based varnish, I’ve used a 3 jar method and my brushes have lasted for many years. Into 3 containers put an equal amount of paint thinner (mineral spirits) and label them 1,2 and 3. I use jars salvaged from pickles but use the container of you choice as long as it has a wide mouth and is resistant to MS. to clean a brush, I first spray it with MS kept in a spray bottle, and then wipe it on a paper towel. Then I dip into container #1 and work the bristles with my fingers (wearing nitrile gloves) to get as much of the finish out as possible. Pull the brush out and squeeze as much of the thinner out as you can. Then on to jar 2, repeat the first process, but then put the handle of the brush between your palms and spin it back and forth in the thinner briskly. Pull it out and squeeze as much of the thinner out as possible. On to jar 3, where the process is only the spinning, and then the squeeze out. At that point I rinse the brush with lacquer thinner (optional step) to remove as much MS as possible, then to a utility sink to be washed out with Dawn and warm water. Squeeze as much water out as possible, then wrap the brush in newspaper with masking tape holding it closed and hang it up. I only do this after the finishing is complete; between coats I stick the brush in a sandwich bag, wrap it tight, and let it sit for the next coat…there is a limit on how they’ll keep like this, absolutely no more than 24 hours. As for the thinner, put the lids on the jars for the next session. At some point you’ll see sludge form on the bottom, this is the resins you’ve cleaned out and there should be a lot in Jar 1, very little in jar 3. Decant the M into another container and clean the sludge out. Put the MS back in, and then top jar 1 off with the MS in jar 2. Then clean jar 2, and top it off with jar 3…fill jar 3 with fresh MS. This isn’t as much drudgery as it sounds, and I’ve pretty much got into the habit of following it. Shorten it up if you want, but it works really well…important for expensive brushes. Now, if you happen to use a water borne finish then soap and water is all you need.

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

View Josh's profile


1226 posts in 2592 days

#4 posted 05-26-2015 04:14 AM

Wow, I really appreciate the help, guys. I will duly not what you have told me.

-- Tree, wood, and box lover from Pennsylvania

View Yonak's profile


986 posts in 1544 days

#5 posted 05-26-2015 01:47 PM

I ve used a 3 jar method and my brushes have lasted for many years.

- Fred Hargis

+1 for this method. Additionally, I add some of the special formula (white .. with a little bit of lubricant) paint thinner to jar #2. If I am doing a job where I will use the same brush and the same finish another day, I will stop at jar #2 and then, when finished, I will clean completely using the prescribed method.

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