Electric guitars, on the face of it, might not seem to have much to do with chemistry. However, the materials that make them up are carefully chosen for their chemical properties, without which they simply wouldn’t function. In this graphic, we take a look at some of these materials, and their typical compositions.
The most important parts of an electric guitar are, of course, the pickups. These allow the vibrations of the strings to be detected, and eventually converted into sound at the guitar’s amplifier. In order to do this, they make use of magnets, and can contain a number of different elements as part of their composition.
The most common alloy (mixture of metals) used in pickups is alnico; this is a combination of aluminium, nickel, and cobalt. Alnico magnets were once the strongest known, but they have since been eclipsed by the rise of the rare earth magnets, which can also be used in pickups. Samarium cobalt magnets and neodymium boron iron magnets can also be used, although are perhaps less common. Additionally, ceramic magnets, based on iron oxide with strontium or barium carbonate, can be utilised.
The pickup itself consists of a long magnet, or a number of cylindrical magnets in a row, around which is a wire coil. The vibrations of the electric guitar’s strings cause changes in the magnetic field of these magnets, which in turn is able to induce a current in the coiled wire. This current is then passed on to the amplifier, which produces the sound. The stronger the magnets used in the pickups, the more sensitive they are to the string’s vibrations.
Of course, for the guitar string vibrations to have an effect on the magnetic field of the pickups, they too need to contain a ferromagnetic metal; this can be either iron, cobalt, or nickel. There are a large number of different string compositions, but often they will consist of steel, a combination of iron, carbon, and sometimes chromium. The chromium can help prevent corrosion, as it forms a layer of chromium oxide which prevents the string from further attack by oxygen in the air. Additionally, the strings can sometimes be coated with various polymer additives to help inhibit corrosion. However, these additives can sometimes have a negative effect on the tone of the guitar.
The lower strings of a guitar (E, A & D) will often have a nickel winding over their steel core. Nickel also makes an appearance in the frets of most guitars, which are commonly made from nickel-silver. Despite the name, this alloy doesn’t actually contain any silver, but is named for its silver appearance. It’s actually an alloy of copper, nickel, and zinc. These nickel-silver frets aren’t as hard-wearing as steel, so some guitar manufacturers use stainless steel instead to give the frets more longevity.
The inlays of the frets can be made from a variety of materials. The pearly effect can be achieved via the use of mother of pearl, also known as nacre. This is a material produced by a number of molluscs, and based on layers of calcium carbonate divided by layers of organic biopolymers. Inlays can also be made of plastic on some guitar models.
From an appearance perspective, at least, the most important aspect of the guitar is the body’s finish. The finish of most electric guitars is either a nitrocellulose lacquer, a polyester, or a polyurethane. Nitrocellulose, for the unfamiliar, is highly flammable and also known as gun cotton. It is obtained by the nitration of cellulose, an important structural component of plants. In guitar coatings, nitrocellulose is blended with other compounds and organic solvents to create a lacquer. The solvents evaporate as the lacquer dries.
Nitrocellulose lacquer is prized as a coating by some guitarists as it is thinner than some other coatings, which some claim leads to a better sound (though we’re not going to wade into that argument here). It’s also easy to blend with paints, and easier to repair. It does have its downsides, however. The solvents used in the lacquer can be potentially damaging to the respiratory systems of workers applying the coating during the guitar’s manufacture, and for this reason other options were sought.
Enter the polyesters and the polyurethanes. These plastics can be made into synthetic resins which harden after application the guitar body, making them more durable than nitrocellulose finishes. In some cases, UV light can be used to initiate the curing process of the resin, making the finishing process much quicker than the application of nitrocellulose lacquer.
It’s clear, then, that, if you’re a guitarist, whilst the sound production of an electric guitar might owe more to physics, the materials that give it the properties that allow for this in the first place owe something to chemistry.
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References & Further Reading
- The science of electric guitars & guitar electronics – J Lähdevaara
- The chemistry of guitar strings – T Parker
- Optimisation and evaluation of stainless steel wire used as guitar strings – S Vosough
- Nitro vs. Poly – G Wahl-Stephens, Pro Guitar Shop