# How to get polyurethane from brush? lacquer thinner isn't working!



## HarryS

So this is my first project ever and I finally laid down the first coat of polyurethane, I knew it would take several hours to dry so I was worried about my brush and wanting to make sure it was good for many future uses since it was a high quality white thistle brush for almost $25.

Well I did buy lacquer thinner and was about to pour it in a bowl to clean my brush for tomorrows second coat (which is today) and I read a "great" post saying to put it in a grocery bag and as long as its used within a day you're fine, well I just opened the bag now really excited to put my final coat and finish my desk only to find my brush hard and crusty! I have left it sitting in lacquer thinner for almost two hours and nothing is really changing, what can I do?! Just one use and I can't even apply a second coat without buying a new one?


----------



## Hammer1

Lacquer thinner is a solvent for lacquer, not polyurethane. It won't do anything. Brush care is important. When the poly was still wet, you can use mineral spirits, (paint thinner), to clean the brush. Now that it's hard, you need to use brush cleaner, which is available at any hardware store. Let it soak in the brush cleaner for a few hours, shake it out, wash with warm water and dishwashing soap. Repeat if necessary. The correct solvent to use with poly is in the directions on the can.


----------



## Steve Neul

For now keep it in lacquer thinner to keep it from hardening anymore. If it was oil based polyurethane you could have put it in a can of paint thinner for overnight purposes. A plastic bag is pretty limited for storage as you found out. Sometimes when I'm working at a customers house I will wrap up a paint brush in a plastic bag so I can wait until I get home to clean it but not overnight. The bag has to be wrapped really tight though to use it for a short storage. 

Now to clean the brush the only option for you now is soak the brush in paint and varnish remover. I will sometimes soak a brush like that and then rinse it off with a power washer. This usually removes all the dried finish that is on it. Sometimes the stripper and power washer will make the brush a little fuzzy so before it dries I wrap the bristles with shrink wrap. Once it dries the brush is nearly good as new.


----------



## epicfail48

I think you're boned mate. Short of soaking it in paint stripper, dried poly ain't coming off, and even if it does come off you still run the risk of missing just a little bit in the cleaning and ending up with a dried poly chip in your finish. 

This is why I use foam brushes for poly


----------



## rjpat

First of all, I cannot see how wrapping it in a paper bag would help, the poly reacts with oxygen to cure and the paper would do nothing to stop the oxygen. Although I have never tried it with poly, I wrap brushes tightly with aluminum foil, seal it in a plastic (ziplock) bag, and store it in the freezer. This will keep it soft for 1 to 2 weeks. As far as this brush is concerned, Lowes, etc. sell a brush cleaner that I have had some success with.

http://www.lowes.com/pd_622066-78-QJBC204___?productId=50298107&pl=1&Ntt=paint+brush+cleaner


----------



## Brian T.

Polyurethane = it _polymerizes_. Molecular cross connections that cannot be easily undone. I predict you're hooped. Expensive lesson.

I rigged up a coathanger to suspend brushes in the required solvent overnight. That can be sopped up with paper towel tomorrow morning for more work. To be honest, I try to get a full coat on whatever and toss the brush.

For wood carvings with MinWax Tung Oil Protective Finish, I use the cheapest crappy brushes (boxes of a dozen) and let them harden up and out they go. Not worth the time & effort to save any of them.


----------



## LostHasher

Hammer1 said:


> you need to use brush cleaner


+2

I know this thread is a couple months old, but I finally tried some of this for my low-cost brushes. One was hardened with urethane. I resurrected enough of them to make the brush cleaner pay for itself. 

There's a reason this stuff works. It's essentially a mad-scientist blend of Things With Deadly Fumes, including toluene, acetone and dichloromethane (paint stripper). Really vile.


----------



## bruceL

I have always used cellulose thinners, but be aware of the fumes and work in a well ventilated area


----------

