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Research bow materials. Decide what size and weight are right for you. Learn about the importance of shaft shape. Study the importance of national origin.
One of the most important factors to consider in buying a bow is what it is made of. Depending on your level of experience, monetary resources, and personal preferences, there are four different choices you could make:  Fiberglass bows are the most inexpensive. They come with many student violins. They are durable and affordable, but not adequate for more advanced players. Brazilwood is the term used to describe bows made from tropical hardwoods. These are inexpensive bows that are ideal for beginners or intermediate players. Pernambuco, a dense, heavy wood from Brazil, has been used in most of the best bows since the 18the century. Pernambuco bows are increasingly rare, due to environmental devastation, and therefore are much more expensive. However, these bows are thought to provide an ideal balance of strength, responsiveness, and elasticity for the advanced violinist. Carbon-fiber bows are built to approximate the qualities of pernambuco, and have become increasingly popular in recent years as the real thing has become harder to obtain. They are a reasonable approximation of their wooden counterparts, and are more affordable and durable. Violin bows come in a variety of lengths and weights, and choosing the right one is important for maximizing your potential as a violinist.  The average adult violin bow weights about 60 grams, and some violinists will not play any bow that strays much from this weight. However, some high quality bows weigh as little as 54 grams, so don't be afraid of a lighter bow. On the other hand, a bow weighing more than 66 to 68 grams will be too heavy for most violinists.  The size of the bow is also important. Too long a bow can be cumbersome for children and other people of smaller build, but a short bow loses some flexibility, thus limiting the range of expression possible.  Anything smaller than 3/4 size will result in a loss of flexibility. The good news is that student learners generally will not have the technical skills required for the sophisticated bow strokes a longer bow allows for anyway. Violin bow shafts come in two different shapes: round and octagonal. Octagonal bows are generally harder to find.  Many violin players prefer the look of octagonal bows. That said, octagonal bows are often stiffer, which decreases the flexibility of a bow and limits some of the nuance that can be achieved in your bow strokes. Especially when buying a vintage bow, many expert players consider the country of origin of the bow to be important.  English bows are almost always made for professional use. Those from the 1920s and earlier are particularly sought after. German bows have a bad reputation because historically, many of the cheap student bows were manufactured there. Even so, there have been many fine German bow makers such as Heinrich Knopf and Otto Hoyer. Vintage French bows are the most sought after (and expensive) of all. If you're buying a newer bow, you can get a close approximation made elsewhere, as the Parisian style of bow-making has spread to the US, the UK, and Ireland.