Woodworker's Journal 1993-17-2, страница 25
so. here are a few basic guidelines: First, you should know the differences between a natural bristle brush and a synthetic bristle brush. When viewed under a magnifier, natural bristles are rough and pitted, rather than smooth, like synthetic bristles. Thus, they hold more material and apply it more evenly. However, natural bristle brushes should be used only with solvent-based finishes (shellac, brushing lacquers, oil-based varnishes and polyurethanes). When used with water-based finishes, the bristles absorb water, which makes them swell and lose their shape. Water-based finishes also "load up" on natural bristle brushes, resulting in uneven coverage and less control when "cutting in" edges. Suffice to say. natural bristle brushes not only perform poorly with water-based finishes, but the water will eventually ruin the brush, making it useless. So, your brush collection should also include a few good synthetic bristle brushes. Most natural bristle brushes on the market use hog or boar bristles. In the brush industry, imported China hog bristles are considered to be the best quality, so my first recommendation is to make sure that any hog bristle brush you do buy has 100 percent China hog bristles. These brushes usually bear the label "100% China bristle." The natural bristle colors arc black, white or gray. Black China bristles are the most common, and usually the highest quality. White China bristles perform just as well as black bristles, but some finishers (especially boat builders) prefer white because any bristles that do shed into the finish will be less noticeable when the it dries. Gray bristle brushes are usually a mixture of black and white bristles. They're generally of lower quality and less expensive than brushes w ith pure black or white bristles. Some lower-quality natural bristle brushes are dyed black: you can often tell because the bristles will feel crusty or unnaturally stiff: in some cases, the dye will transfer to your hand when you rub the bristles. Some higher quality China bristle brushes may also be dyed; these usually have white bristles that are dyed a brown or golden color. I might add here that hogs, like people, don't all grow exactly the same kind of hair. For example, hogs in the southern Chinese provinces tend to have thicker, stiffer. bristles than hogs in the northern Chinese provinces. Also, hogs don't grow hairs all the same length or color. As a result, brush manufacturers are able to mix March/April 1993 Please circle No. 8 on the Reader Sen il e Card 25 FJSR&JV^. — ^.-iahmue** and match hog bristles of different lengths and thicknesses to make brushes w ith different performance characteristics. Some very expensive natural bristle brushes include a mixture of China hog bristles and softer ox hair, skunk hair or badger hair bristles. Such brushes tend to be softer than 100 percent China bristle brushes. Generally, these brushes work best with stains and thinner finishes such as shellac and brushing lacquers because they hold material better and flow on the finish more smoothly. A top-quality varnish brush of this type usually contains a mixture of 20-30 percent ox, badger.W skunk hair bristles in proportion to China hog bristles. These blended bristle brushes aren't as common as they were several decades ago, so you probably won't find them at your local hardware store or home improvement center. However, several of the companies listed in Sources make them. Beyond the type of bristles used, performance is determined by the mixture of bristles (short and long l the amount of bristles (fill), the overall length of the bristles in relation to the width of the brush, the amount of flagged bristles at the tip of the brush, and the thickness of the individual bristles themselves. Veteran finishers learn through experience how particular types of natural bristle brushes perform with various types of finishes. Some finishers like softer brushes: others like stiffer brushes. For example a full, long-bristled brush with softer, pliable bristles and heavy flagging will probably work better with shellacs and fast-drying brushing lacquers, which require flowing on the finish in long, quick, even strokes. A short-bristled brush with thicker individual bristles would be preferable for applying slow-drying oil varnishes or polyurethanes that require a certain amount of "hard" brushing to apply the finish and eliminate bubbles. While the veteran finisher can often judge the performance and quality of a brush just be feeling the bristles, the price of the brush is also often a good indicator of quality. Realistically, the weekend finisher probably won't notice much difference in performance between a good consumer-quality China bristle brush and a top-end handmade $30 China bristle brush. Synthetic Bristle Brushes Synthetic bristle brushes also vary in quality, although the quality difference is produced by artificial means, rather than UMiWt.MO VMtJirtM - -----,+ HOLE, yn uwtis Tee, maALsrtwe, |
