Wooden Boats: Building and Repair/Painting and Varnishing/Brushes
Brushes for Varnishing
Which kind of brush to use is a matter of personal opinion and depends upon the job. For a lot of jobs, cheap foam brushes will suffice. Foam brushes should not be used for long before being replaced. The brush you use is unlikely to make that much difference to the job unless you are an experienced varnisher. The preparation work, mix of varnish and temperature probably have more of an effect on the end result than the brush. The idea of a dedicated varnish brush is that you should be able to make long uninterrupted strokes without having to refresh the brush.
If you use a brush with bristles, it is worth investing in a good quality one, if only for the reason that when cheap brushes lose their bristles they make a mess of the work. Loose bristles can be dislodged ahead of time by gently rubbing and rolling the brush against some sandpaper. Some say that a dab of varnish in the heel of the brush can help to keep the bristles in.
Foam brushes are not as well suited for larger surfaces and jobs, where it is important not to have any runs. Good china bristle brushes are better in these circumstances. Foam brushes are fine for patching in and quick jobs on small work pieces. Rebecca Wittman, the author of 'Brightwork' uses "Jen" poly-foam brushes (they do not turn to mush when used with epoxy). It is possible to buy really expensive bristle brushes, but it is not necessary to go beyond Hamilton, Epiphanes or Omega to get the best job that you are capable of. The best varnish brush is one that will hold a full load of material, without drooling and dripping from the can to the work surface and will feather the flow out evenly. Foam brushes don't offer the control needed because the varinish lays on the surface of the brush and not within the fibers that a bristle brush has. China boar bristles are best because the ends are split into flags.
Good brushes don't swell and they regain their shape quickly. Good brushes can last for a very long time, decades in fact. Don't let them soak and comb them out frequently, to stop a skin from setting around the high tide mark. A needle sharp paint comb, the sharpest one you can buy, is very good if you are a brush user, Don't forget how sharp the combs are.
How to keep a brush pristine for over 40 years
The following was posted by Jay Greer on the WoodenBoat Forum:
My own Linzer China Boar Varnish Brushes with soldered ferrells are no longer made. I have cherished and kept them pristine for use for over forty years, as follows.
All of my brushes are stored under thinner in two one gallon, wide mouth commercial salad dressing plastic jars, one for paint and one for varnish brushes. After use, the brushes are given no less than five rinses in thinner stored in three 5gallon paint buckets. The last two rinses are with fresh thinner. The brushes are then wrapped in the porous black paper used for scrap books and photo albums and placed tips down in the storage container. This manner of storage keeps the chisle edge of the brushes intact.
Once a year or when the heels get too filled with excess varnish or paint, I soak the bristles in liquid sandpaper to soften the heels and brush out the residue with a fine wire brush. This takes several soakings and several brushings. Then, while standing at a beam of light comming through a crack in the shop door, I flip the hairs of the brush until no flakes of varnish can be seen floating in the sun beam.
Sadly, brushes made today are no longer of the fine quality of the old Linzers. I treat them like they were my best friends because they still earn their keep! Jay Greer/Common Sense Boat & Tool Co.