I am in the process of applying polyurethane to a bunch of wood in the basement (trim, doors, wainscot, etc.). Yesterday was the first day of doing this job. When I was finished I put the brush in a small jar of acetone and swished it around for about a minute, ran the brush under tap water for another minute, and then set it aside to dry.
I just went down to the basement to continue the job, only to find the brush’s bristles were stiff. :mad:
So is there a way to effectively clean a paint brush? Or do I need to use a new brush for each session?
I thought about leaving the brush in the acetone, but wouldn’t the acetone just evaporate away?
You might try more acetone (or whatever is recommended on the package of polyurethane) and use a wide-gauge steel comb to strip any chunks from the brush. Ideally, you then wrap the bristles with newspaper or waxed paper and fasten with a rubber band so that the bristles all stay straight.
I would follow up the solvent with plain old dishsoap. An old artist’s trick to get the brush free of any remaining solvents is to slap the bristles rapidly back and forth against a piece of wood. Grasp the brush by the handle and then pretend you are going to paint a very small part of the board at Superman speed. Bappitbappbitybappity. Don’t do this in your kitchen, by the way. Here is a site that has some tips.
For water based, I use soapy water at the sink and rinse well.
Your poly must be solvent based (check) and so mineral spirits or paint thinner is the preffered method, not acetone. First paint out or dry the brush as much as possible with a rag before cleaning in the spirits. You can keep a jar of spirits for reusing as brush cleaner. After swishing in the spirits, paint out or dry the brush again and repeat. Rinsing that solvent based soaked brush in the sink was not kind to the environment even after you had pre-cleaned it.
Make sure you are using the appropriate thinner/cleaner. Check the label of the product you are using, it should tell you what to use
Spend more time cleaning the brush next time. Two minutes isn’t really sufficient for a thorough job.
It’s totally OK to use disposable brushes. Ask at the hardware/DIY store, disposable brushes are usually foam and cheaper than traditional brushes, and come in a variety of sizes.
IANA expert, but for any oil-based product I’ve always considered the brush to be a single-use item. It’s just too difficult, and takes too much solvent, to get the brush really clean enough to use again tomorrow.
With the material costing $30/gal or more, spending $4 on a medium quality brush isn’t too much to ask. On a surface I cared about I’d never use one of those sold-as-disposable-for-98-cents brushes/foam pads. You’ll really see the difference in your coating quality.
I clean out paint brushes regularly for my job. We almost exclusively use polyurethane based finishes. The first thing I do is brush it with a wire brush and dip it in a can of paint thinner. Then I have a “spinner” tool. Basically you stick the brush on the end of it and pump the handle and it will spin all the thinner out of the brush (usually done in a 5 gallon bucket so the spray doesn’t go everywhere.) Repeat the dip & spin process a few times. Finish with fresh thinner.
If you’re using the brush again the next day, just soak the brush in thinner and spin it out before you use it. Make sure the brush is sticking straight up or you’ll have warped bristles the next day.
We reuse our brushes probably a hundred times using this method.
You don’t want to use water on brushes you use for oil based finishes.
Not to insult your intelligence, but what kind of brush did you use? Only a natural-bristle brush should be used to apply oil-based urethane finish. That said, acetone is a poor choice for cleaning up, as it’s very volatile (evaporates fast, concentrating solutes) and not a great solvent for PUR anyway. Also, I personally have never seen good cleaning result from soaking – immediate and thorough cleaning and rinsing, yes, but soaking seems to ruin everything.
I used a new brush today. It was $8, and the packaging said it was designed for applying polyurethane.
I first used some paper towels to squeeze the polyurethane out of the bristles. (Thanks Al Bundy.) I then aggressively swished it for 3 or 4 minutes in acetone. (Yes, I should use a better solvent.) Finally, I cleaned the bristles in my utility sink using a bristle brush, soap and water, then hung the brush from a hook. I’ll find out tomorrow if it worked.
I like **Evil Jon’s **suggestion of using a steel brush. Will try that next time.
I always rinse three times. Each time using a cleaner solvent. And I reuse the solvents. Dip the brush all the way into the solvent then work the brissles to bemove material, redip the brush. Remove the solvent in the brush, the spinner is the best way or shake the brush (messy). Repeat in the second solvent, then the third. the last was needs to be fairly clear of product.
If you’re doing a multi day project you can just wrap the brush (with poly still on it) in saran wrap. It will still be soft the next day. It will eventually harden, but overnight it will be fine. At the end of the project I clean it real well by multiple cleaning passes in paint thinner. I dump the thinner and pour new a few times to be sure the last cleaning pass is in clean thinner with no dissolved poly/paint.
Hmm. I saw foam brushes in the store, but figured they wouldn’t do a good job since they’re so cheap. (Rightly or wrongly, I often equate high price with better performance.) I’ll give them a try. Thanks.
You can also try using a ‘wipe on’ poly.(Or dilute the poly you have 2 or 3 to 1 with mineral spirits.) I don’t like to wipe on anything big like a table top, but for table legs and other small items wiping it on works well. The coats are thinner, but that often helps with non-horizontal sufraces.
I can’t clean a brush to save my life, so I avoid using them whenever possible.
If you do use a wipe on poly, make sure to let the rags dry flat. If you throw them in the trash, they can catch fire.
Hey, I paint for a living now (among other things). For some materials, like Rustoleum or enamel. I use ONLY foam brushes and toss 'em when I’m done. Foam brushes don’t drop bristles and they don’t normally leave brush marks, so it can result in a very smooth coating.
Actually, with foam brushes I’ll paint all morning, toss, go to lunch, come back, and paint all afternoon with a fresh brush because they’re cheap enough to do that.
If you just want to keep a brush with paint in it overnight, without letting it dry out:
I’m an artist, and most of the brushes I use are very small. I bought a box of cheap disposable plastic gloves. When I need to keep a brush overnight, I cut off a finger from one of the gloves, insert the brush into the finger, and close it tightly with a rubber band. I use the tiny rubber bands that some people use for their hair.
I’ve done the same with larger brushes (using a baggie), and even small rollers.