To the casual observer, a violin is made of wood and a few metal parts, including the strings. However, this is just a small part of its makeup. There is a world of difference in woods and strings, because each has its own structural and sound qualities. There is even a difference in sound quality between old wood and new wood of the same type (for example, old maple vs. new maple). An experienced violin maker (called a luthier) knows these differences, and chooses the best materials for a great-sounding violin.
Violin Top
The violin top is made of spruce. According to master luthier David Gusset, the spruce should be from a very old tree, cut down during the winter, and seasoned, or allowed to sit so it can dry out, for at least several years. The best wood is seasoned for 10 years or more. The grain (the dark growth rings) should be packed as tightly together as possible. These qualities will bring out the best sound.
Violin Back
The back is made of maple. Gusset again recommends using a tree as old as possible, one that's allowed to season for 10 years or more. He recommends that the wood be quarter-sawn. That's when the log is split into fours longways, then the boards are taken off each quarter.
Violin Neck
The neck is maple, again quarter-sawn and allowed to season. It should be free of imperfections, such as knots. Another aspect is the grain must be vertical. What this means is that if the neck was sawn across, the cross-section would reveal the grains running perpendicular to the fingerboard instead of parallel to the fingerboard.
Fingerboard and Tailpiece
The fingerboard is made of ebony. The tailpiece is ebony or maple, dyed black. Cheaper violins have boxwood for the fingerboard. Since ebony is never purely black, most luthiers use black dye to make it uniformly black.
Strings
Strings are usually made out of high carbon steel. These are similar to guitar strings. Early violins used gut (animal intestine) strings, and some players prefer the sound of modern nylon, which mimics the sound of gut.
Varnish
X-ray analysis revealed that early violins kept in the Museum of Music in Paris had mercury, lead and iron in the formulas. Since these substances are extremely toxic, today's modern varnishes re-create the early finishes, but with non-toxic chemicals.