Varnish Brush Care

Lucy Hull

The photograph above shows all the ingredients and equipment used for Bart Chapin’s method of varnish brush care—sans the bucket used for spinning and the bucket used for varnish. Chapin swears by this method, which he’s used to work on his extensive fleet of boats large and small.

How To Take Care of Varnish Brushes

Good varnish brushes are an investment. The Wooster Brush Company’s natural-bristle brushes come in a wonderful variety, the best of which can cost more than $150. I typically use so-called badger-hair brushes, which are usually made of hog bristles colored to look like badger hair. They cost $10 to $25 depending on the size.

I keep a 1½” and a 2″ brush in a repurposed juice container most of the time. I don’t often use disposable bristle brushes because they tend to lose bristles no matter how many you pull out before use. I use disposable foam brushes for small projects, but have found that good-quality bristle brushes are a key element of a smooth, level, and blemish-free varnished finish.

In order to protect my investment in good brushes, I’ve adapted techniques described by Maynard Bray about a decade ago (see WoodenBoat No. 111) to keep them clean, soft, and ready to use.

Gather Your Materials

• Good-quality brushes
• Tall container (I use a plastic juice container with an airtight top)
• Raw linseed oil (boiled linseed oil will eventually harden; raw oil will not)
• Brush spinner
• Bucket
• Clean kerosene in a one-gallon jug (this is cheaper than paint thinner and works just as well for cleaning brushes)
• Empty gallon jug (for used kerosene)
• Various sizes of glass jars with wide mouths and tight-fitting lids
• Rubber mallet (for closing varnish cans)
• Paper towels
• Clean rag

7 Tips on Varnish Brush Care

1. Soak the Brushes in Linseed Oil

Clean the old juice container and then fill it with enough raw linseed oil to cover the bristles to the end of the ferrule—the metal that connects the handle and the bristles—of the largest brush. The container must be tall enough to allow the brushes to stand upright. The oil tends to float the brushes, which keeps the bristles from bending and making it unnecessary to hang the brushes.

Place all the brushes you want to use for varnish in the juice container. They should be clean or new before you immerse them in the oil.

2. Prepare the Brush You Want to Use

Remove the brush you want to use and wipe off as much of the oil possible on the rim of the juice container. Squeeze out the rest of the oil by pinching a wad of paper towel over the bristles. If you have kerosene left over from the last brush you cleaned, use that for the first rinse. If not, fill one of the glass containers with about 2″ or 3″ of clean kerosene.

3. Rinse the Brush With Kerosene

Swish the brush in the kerosene and spin it inside the bucket. It is easier to put the brush in the spinner before you swish it in kerosene. For large brushes, forming a chisel point on the end of the brush handle makes it easier to get the brushes into the spin-ner. With small brushes, one rinse and spin suffices. For large brushes, rinse and spin twice. Put a lid on the jar and save the used kerosene for later.

4. Test the Brush Before Using

The brush is now ready to use. There may be a little kerosene left in the brush, therefore it is best to brush out some varnish on a clean surface before start-ing to varnish. Pour the amount of varnish you estimate you will need into a small glass jar. (Varnishing straight out of the can risks introducing contaminants to your varnish and can be messy.) Add your preferred thinner and other ingredients, if you’re using any, to the varnish, and stir.

5. Take Care When Varnishing

I usually place the jar inside a paint bucket; this reduces the risk of knocking over the jar and catches any drips that come off the brush. You may want to brace the jar inside the bucket in some manner—say, by wrapping it in an old towel—so that you can wipe the brush on the edge of the jar without tipping it over. If I have several jars of varnish with various amounts of thinner, I mark the tops of the lids accordingly.

Once the varnish job is done, I wipe the rim of the varnish jar with a clean rag or paper towel and put a lid on the jar. If the rim of the jar is not kept clean, varnish will ball up and chunks of hardened varnish will appear in subsequent work. If I am going to varnish again soon and there is a good amount of varnish in the jar, the varnish will keep for a day or so. If there is just a small amount of varnish in the jar, the varnish will skim over with surface film.

I try not to pour anything back into a varnish can because it will add dust and other unwanted ingredients to the untouched varnish. If there is just a small amount left in the jar, empty it out into an open container and let it harden. Then swish a bit of kerosene around inside the jar and leave it there. Pour the kerosene out into the used kerosene jug just before using the jar again for varnish.

6. Squeeze Leftover Varnish Off the Brush

When you have finished varnishing, squeeze as much varnish as possible out of the brush into a folded clean paper towel. It might take a couple of tries to get most of it out of the brush. Put the brush in the spinner and swish it in the used kerosene that you reserved after you took the brush out of the linseed oil.

7. Clean the Varnish Brush

Spin the brush in the bucket. Pour the used kerosene into the gallon jug dedicated for that use. I mark the jugs so that I don’t mix them up. Pour some fresh kerosene into the jar and swish the brush. Spin the brush again and put it in the juice container. Keep the used kerosene from this second spinning for the first wash the next time around.

Keep Your Varnish Brushes in Good Shape for Years

I have kept brushes in this manner for many years without cleaning them further and with no ill effects. Sooner or later brushes will load up with hardened varnish near the ferrule. This has started to happen to a couple of brushes I have used for seven or eight years; these brushes can be used on less critical projects or for painting.

Once you have used this method for varnish brushes, the brushes cannot be left out of the linseed oil. There is varnish in the brush up next to the ferrule and it will harden if left to dry. The oil keeps the varnish from hardening.

I find that brushes do better as they age. As they wear, they become smoother and softer, and the oil tends to help with this. Also, most of the bristles that are going to fall out of a brush will do so during the first couple of uses.

One Last Tip

A word of caution about the paper towels used to remove varnish from brushes: These will catch fire if you wad them up and keep them in a confined space. I throw mine in the woodstove or a bucket of water almost immediately after use.

With an indelible marker, write the date you purchased the varnish on the lid of the can. Then you know which can to open next. When you open the can, mark the date you opened it on the lid.

Bart Chapin is the sole proprietor of a machine automation and design company. He has owned, repaired, built, rowed, and sailed boats from a young age. He and his wife, Lucy, own two Beetle Cats, two kayaks, a Nutshell pram and a 34′ sloop.

Need More Varnishing Advice?

For more details on varnishing and painting, check out these guides from WoodenBoat and Small Boats.

Varnishing Basics: A Guide to the Instructions on the Can

Varnish Repair and Maintenance Coats: A general outline of the process for a basic annual-maintenance varnish job

Wiping Varnish: Final coats fast and close to flawless