Understanding Materials: Graphite

Most of us have heard about graphite necks and graphite bodies. Flea [bassist the Red Hot Chili Peppers] is often seen playing a Modulus with a graphite neck, so is Oteil Burbridge, Stefan Lessard, and many others. [Who bassist] John Entwistle even had a whole bass made from graphite. Some companies use graphite for the body, many use it for the neck, and many more us graphite rods to make wooden necks stronger. Both Status Graphite and Moses Graphite offer replacement graphite necks for your bass, as well as graphite bridges and nuts. Steinberger and Modulus are two household name companies that use graphite to a large extent in their basses. So, what exactly is graphite, and why is it a good material for basses?

As a material, graphite belongs to the large family of ceramics. Other common materials on this family include silica, glass, and diamond. Graphite is a form of carbon with characteristics like high electrical and thermal conductivity, and high thermal shock resistance. More correctly, graphite is a crystalline form of carbon. What this means is that graphite has a layered structure with sheets of close-packed carbon atoms. The look of pure graphite can be compared to wood where the grain in the wood all go in one direction, but remember that in graphite this is all happening on a microscopic scale. Because of this structure, graphite is a brittle material (compare it to the glass plate you eat dinner from every day. It breaks into a million pieces if you drop it on the floor, but try pulling it apart with your bare hands. Bet you can't do it, hehe...) It is especially weak if you shear it along the layers. The led in your pencil is a mixture of graphite and clay, as you know, pencil led wouldn't make a very stable neck for a bass. So why do people insist on using graphite as a bass material? We'll get to that in a minute, but first I'll just mention one of the most important uses for graphite: it is used as fibers in reinforced plastics and composite materials.

A composite material is a material that is made up of two or more other materials that won't dissolve each other when mixed. When put together, a composite material is far stronger than any of it's components. This is where graphite comes in. It is used as a fiber in composite materials. Although graphite is a brittle material, it has a very high strength-to-weight ratio, and also a very high stiffness-to-weight ratio. A composite material is, very simply put, made by two components. The first is the fiber, the other is the matrix. The matrix is some kind of plastic, either a thermoset or a thermoplastic. The matrix is very tough, but not very strong and stiff. If you mix in some fibers (remember, graphite fibers are strong and stiff, but not very tough) you get the best of both worlds. The resulting material is strong, stiff, tough, and very light. The job of the matrix in this composite material is; to support the fibers and transfer stress to them so they can take most of the load; to protect the fibers from physical damage from the environment; and to reduce the propagation of cracks. The fibers are mixed into the matrix when the matrix is heated and has a consitancy like cookie dough. The fibers are stirred into the mix, either as small particles, flakes, or continues strands. When the matrix and fiber mixture is baked in a very hot oven, the whole thing locks together, and the graphite fibers gain strength and stiffness as the temperature rises. After the composite has cooled down again, this added strength and stiffness is locked into the material. Composite materials like this is used for all kinds of things. The aircraft industry and NASA have many uses for it, mountain bike frames are common uses, race car parts, and of course bass necks. The hulls of plastic leisure boats are also made from a composite material, glass fiber. Surfboards are reinforced with composite materials around a foam core, and so are alpine skis. Glass fiber is probably the most commonly known composite material, and it works well to illustrate the concept of mixing fibers with a matrix to gain strength and lightness, as most of us has seen raw glass fiber one time or another. For basses, the composite used is made from strands of graphite mixed into a plastic matrix.

So, the term graphite neck is a little misleading. Graphite is only part of the equation when it comes to composite necks. A neck made from pure graphite wouldn't last long if you added the load of 4 chunky bass strings. To recap, the graphite part makes the neck stiff and strong, and the plastic matrix part makes it tough. The resulting composite material gives you a neck that is strong, almost non-reactive to changes in temperature and humidity, and very long lasting. Bass manufacturers usually add a fingerboard of some suitable material, and a few coats of clear finish before the neck is ready. The fingerboards used on composite necks are often made from other composite materials or plastics, and on some rare occasions a high quality wood. If you add a normal rosewood fingerboard to a composite neck, you might have trouble keeping it on. This is because wood is living material. It expands and contracts as the temperature and humidity changes. Composites on the other hand, are dead materials. They stay the same regardless of temperature and humidity. The fact that the wooden fingerboard wants to move, but it can't since it's attached to a dead neck, causes stress in the whole neck and things can end up broken. The advantages of composite material necks are many. The consistency in production is very high, so all the necks from the same production line are the same. The mass is the same all along the neck, and this in turn reduces the chance of dead-spots occurring. They are also extremely resistant to changes in temperature and humidity. Not all composite necks are the same though. The different manufacturers use different materials for the matrix, and probably a different mixture of fibers. The resulting composite is just as good as any other, but has a different sonic character. Because of this, there is a difference in sound between a Moses, a Status and a Modulus neck even though they are all made from a composite containing graphite. So, for your next bass, consider composite materials as well as the more traditional woods. You might find something you like.