I’ve ruined a few good brushes over the years by letting polyurethane dry in them — including one I used on my outdoor coffee table build. Polyurethane brings out the natural beauty of wood and protects it for years, but it’s tough on brushes if you don’t clean them right away. Once the bristles harden, the brush is done, and you’ve basically thrown money away.
The good news? With the right cleaning method, you can keep your brushes in great shape and reuse them for multiple projects. In this guide, I’ll walk you through how to clean both water-based and oil-based polyurethane brushes step by step, how to store a brush between coats, and what to do if your brush has already dried out.
Quick Overview: How to Clean Polyurethane Brushes
If you just want the short answer, here’s a quick comparison of the best ways to clean polyurethane brushes depending on what type you’re using:
| Type | Best Cleaning Method | Difficulty | Notes |
|---|---|---|---|
| Water-Based Polyurethane | Hot water (with or without mild soap) | Easy | Cleans quickly, safe for synthetic brushes |
| Oil-Based Polyurethane | Mineral spirits or paint thinner | Moderate | Strong odor, requires ventilation & gloves |
| Dried Polyurethane | Soak in solvent (spirits or thinner) | Hard | Needs soaking and combing out bristles |
| Alternative Option | Heated vinegar | Moderate | Non-toxic, but slower and less effective |
Table of Contents
- General Questions
- What is polyurethane?
- What brush should you use?
- Why clean brushes right away?
- How to store between coats
- How to clean water-based polyurethane from your brush
- Method 1 – Clean with Hot Water
- Method 2 – Clean with Hot Water and Soap
- How to clean oil-based polyurethane from your brush
- Method 1 – Cleaning with Mineral Spirits
- Method 2 – Cleaning with Paint Thinner
- Method 3 – Cleaning with Vinegar
- Top Products to Clean a Polyurethane Brush
- How to clean dried polyurethane from your brush
- Wrapping up
- FAQ
📌 Save this guide for later!
Pin it to your woodworking board so you’ll always know how to clean polyurethane brushes.
What is polyurethane?
Polyurethane is a clear finish that protects wood while enhancing its natural beauty. It comes in two types:
Oil-based – tougher, slower to dry, amber finish, better outdoors.
Water-based – faster drying, low odor, clear finish, ideal indoors.
Both can make your projects look great, but they also make brushes tricky to clean.
What brush should you use?
Natural bristle → best for oil-based poly, smooth finish.
Synthetic bristle → works for both oil and water-based, easier to clean.
Foam brush → cheap, disposable, good for quick touch-ups (I use them on small jobs).
| Brush Type | Oil-Based Polyurethane | Water-Based Polyurethane | Best Use |
|---|---|---|---|
| Natural Bristle | Excellent | Poor | High-quality finish, oil-based only |
| Synthetic Bristle | Good | Excellent | Versatile, easy to clean |
| Foam | Fair | Fair | Quick jobs, disposable |
Why clean brushes right away?
Prevents bristles from hardening.
Saves money (good brushes are expensive).
Keeps the finish smooth on your next project.
How to store between coats
If you’re recoating within a few hours:
Wrap the brush tightly in plastic or aluminum foil.
Store in the fridge to keep it from drying.
If it’ll be longer:
Clean it right away using the right method for water or oil-based polyurethane.
How to Clean Water-Based Polyurethane from a Brush
Water-based polyurethane is the easiest to clean. Do it right away before the finish hardens:
Method 1 – Hot Water
Wipe off excess polyurethane with a rag or paper towel.
Rinse the brush under hot water, working the bristles with your fingers.
Repeat until the water runs clear
Method 2 – Soap and Water
Mix a few drops of dish soap in warm water.
Swirl the brush in the soapy water, then rinse with clean water.
Repeat until no residue remains.
👉 Tip: Synthetic brushes handle hot water best. Clean them immediately after use to avoid stiff bristles.
How to Clean Oil-Based Polyurethane from a Brush
Oil-based polyurethane won’t wash out with water — you’ll need a solvent. Always wear gloves and work in a ventilated area.
Method 1 – Mineral Spirits (Most Common)
Wipe off excess polyurethane with a rag.
Swirl the brush in a small container of mineral spirits.
Work the solvent through the bristles with a brush comb.
Wipe clean on a rag and repeat with fresh spirits until the brush is clear.
Method 2 – Paint Thinner
Dip the brush in paint thinner, swirling to loosen residue.
Comb through the bristles, then wipe on a clean rag.
Rinse with warm soapy water to remove leftover thinner.
Method 3 – Vinegar (Safer Alternative)
Heat vinegar in a pot until warm (not boiling).
Soak the brush for several hours.
Rinse with warm soapy water and reshape the bristles.
👉 Tip: Vinegar is non-toxic but less effective than solvents — best for light cleanup or when you want to avoid harsh chemicals.
Note on disposal: Never pour used mineral spirits or paint thinner down the drain. Let the container sit until solids settle at the bottom. You can reuse the clear liquid on top, and dispose of the sludge safely at a local hazardous waste facility.
Top Products to Clean a Polyurethane Brush
There are plenty of cleaners and solvents on the market, but not all of them are equal. Here are a few I’ve tried or seen commonly used, along with what they work best for:
| Product | Best For | Notes |
|---|---|---|
| Klean-Strip Odorless Mineral Spirits | Oil-based polyurethane | Low odor, effective cleaner, widely available |
| KRUD KUTTER BW32 Brush-Wash | Both water & oil-based | Restores hardened brushes, biodegradable formula |
| Sunnyside Mineral Spirits | Oil-based polyurethane | Budget-friendly, strong solvent, use with ventilation |
| Winsor & Newton Brush Cleaner & Restorer | Dried brushes | Gentler option, works well for restoring fine bristles |
| U.S. Art Supply Brush Cleaner & Restorer | Dried brushes | Good for hardened bristles, non-toxic formula |
How to Clean Dried Polyurethane from a Brush
Sometimes life happens — you put the brush down and forget to clean it. Don’t worry, a dried polyurethane brush isn’t always a lost cause. With some patience, you can often bring it back to life.
Steps to restore a dried polyurethane brush:
Scrape off excess – Use a scraper or the edge of a putty knife to remove hardened polyurethane from the bristles.
Soak the brush – Submerge it in mineral spirits or paint thinner for at least an hour to soften the residue.
Comb the bristles – Gently loosen the polyurethane with a brush comb or old fork. Be careful not to pull too hard.
Wash and dry – Finish with warm soapy water, reshape the bristles, and let the brush dry fully before storing.
👉 Tip: The longer polyurethane sits, the harder it is to remove. Cleaning your brush right after use is always easier and cheaper than trying to rescue it later.
Wrapping Up
I learned the hard way that not cleaning a brush properly means throwing money away — I once ruined a brand-new natural bristle brush I had used on my outdoor coffee table build. Polyurethane gives wood a durable and beautiful finish, but it’s unforgiving on brushes if you don’t act fast.
The takeaway is simple:
Clean water-based polyurethane with hot water (a little soap if needed).
Clean oil-based polyurethane with mineral spirits or paint thinner (or vinegar if you prefer a safer option).
Don’t wait — the sooner you clean, the easier it is.
Good brushes are an investment. If you take care of them, they’ll serve you across many builds — whether you’re finishing furniture, protecting outdoor projects, or even working on shop jigs. If you want more practical guides like this, check out my free woodworking plans and start your next project with the right tools and know-how.
FAQ: Cleaning Polyurethane Brushes
Can I reuse a polyurethane brush?
Yes — if you clean it right away. A good-quality brush can be reused many times for both oil-based and water-based polyurethane as long as it’s cleaned and dried properly after each use.
How do you store a polyurethane brush overnight?
If you’re applying multiple coats in one day, wrap the brush tightly in plastic wrap or aluminum foil and store it in the fridge. This prevents the polyurethane from hardening between coats. For longer breaks, always clean the brush first.
Can I use vinegar to clean polyurethane brushes?
Yes — heated vinegar is a safer, non-toxic option for cleaning oil-based polyurethane. However, it’s slower and not as effective as mineral spirits or paint thinner. It’s best for light cleaning or if you want to avoid strong solvents.
What is the best solvent to clean oil-based polyurethane brushes?
Mineral spirits are the most common choice. They dissolve polyurethane effectively and are easier to find than specialty cleaners. Just remember to work in a well-ventilated area and wear gloves.
