Gutta-percha

Gutta percha seems to be a variety of latex, related to but less elastic than caoutchouc (which I mention only because I love the name). Gutta percha comes from the sap of a Malaysian tree; one source says Palaquium gutta¹, another says Isonandra gutta²; in any case, the harvesting process kills the tree. It was first brought to European notice in 1843. "Percha" may mean Sumatra; then again, it may mean "a rag or remnant"². "Gutta" may be an English corruption of the Maylay "getah", meaning "sap".

This is the substance used to fill the root canal of teeth after root canal therapy. It is pink, and has some barium added to it to make it radiopaque (show up white on x-rays). It is a rubbery substance, and is put in the tooth in the form of points, or little spears, and seared off with heat.

In his Latin sentences he found the parts fit into each other like dovetailing; finding the terms of equations, he said, was like inventing machines, and he soon grew clever at solving them. It was not from his manual abilities alone that his father had given him the name of GuttaPercha Willie, but from the fact that his mind, once warmed to interest, could accommodate itself to the peculiarities of any science, just as the guttapercha which is used for taking a mould fits itself to the outs and ins of any figure.

- from Gutta-Percha Willie by George MacDonald

In my office, I have a desk that was made by my great-great-grandfather. I've had it since I was a kid. Clearly, my parents have no respect for antique furniture. The desk is unremarkable, except for the drawer pulls. There are eight of them, all alike, seemingly carved in an intricate pattern of leaves and berries. People who see the desk usually ask me if my great-great-grandfather carved all those drawer pulls. The answer, of course, is no. He didn't. They look like wood, but upon closer inspection they reveal themselves to have been stained or painted to give them that appearance. Furthermore, a trained eye can see that they've been cast in some sort of mold. They're gutta percha!

What is it?

Gutta percha, also known as Gutta-percha, gutta-taban, gutta-percha depurata, and gummi-plasticum, is a rubbery substance made from the latex-bearing sap of Palaquium Gutta or Isonandra Gutta trees. The trees are native to the Malayan archipelago, especially Singapore, and the name "Gutta percha" is generally agreed to have come from the Malay words "getah" (sap) and "perca" (strip of cloth).

Gutta Percha was one of the first natural plastics to be exploited by man. Chemically, it is the same as that other tree extract - rubber - but the shape of the molecule gives it different properties. It is usually dark brown in color. It softens in warm water, can be molded into whatever shape you like, and is hard but not brittle when it cools. It has a tendency to deteriorate in direct sunlight.

Uses

Gutta percha is a good electrical insulator. It's also waterproof. The fact that it deteriorates in sunlight doesn't matter when it's underwater. So one of the the first uses of gutta percha was as a sheathing for transatlantic telegraph cables. By the end of the nineteenth century, over 250,000 miles of gutta-percha-insulated telegraph cable was in use. This application continued for 100 years, until polyethylene replaced gutta percha as the insulator of choice.

It wasn't long before people began to find other uses for gutta percha. By 1850, it was being used for so many purposes that cartoonists regularly made fun of its ubiquity. Jewelry and golf balls were two particularly popular applications.

These days it's mostly used by dentists to make temporary fillings. The name Gutta Percha is often used to describe any dark coloured Victorian molding material, from horn to shellac and Bois Durci to genuine gutta percha. So if you find something in an antique shop that's labelled gutta percha, it may actually be something else.

How is it made?

Latex, collected by felling or girdling the tree, is allowed to coagulate. It is then put into a pot of warm water and kneaded to remove particles of wood and bark. This process is repeated several times, and then the mass is molded into bricks for shipping.

Aggressive harvest of gutta percha has made the trees almost extinct. Efforts are underway to breed the tree in China, where it is valued for its medicinal uses.

Possibly the oldest known form of natural rubber. Due to its stiffness, it takes the back seat to heva rubber. Unlike heva rubber, one of it's main components is trans-polyisoprene. Most of the polyisoprene in heva rubber has a cis conformation. In its raw form, it is a milky white substance.

• Rubber Balls
• Submarine Cable Insulation
• Golf Balls
• Temporary Dental Fillings

Isonandra Gutta trees from the Malay peninsula.

It was introduced to The Royal Society of Arts in London in 1843 by William Mongomerie. That same year, it was used to insulate the telegraph lines along the Great Western Railroad.

S.W. Silver & Co. and company invented a method to extrude it over wire in 1845.

It softens substantially at 71°C and can be formed into many shapes by compression molding or by hand-working at that temperature. It can be cut easily at 60°C.

http://www.azom.com/details.asp?ArticleID=1456

http://collections.ic.gc.ca/cable/gutta.htm

Gut"ta-per`cha (?), n. [Malay gutah gum + pertja the tree from which is it procured.]

A concrete juice produced by various trees found in the Malayan archipelago, especially by the Isonandra, or Dichopsis, Gutta. It becomes soft, and unpressible at the temperature of boiling water, and, on cooling, retains its new shape. It dissolves in oils and ethers, but not in water. In many of its properties it resembles caoutchouc, and it is extensively used for many economical purposes. The Mimusops globosa of Guiana also yields this material.

© Webster 1913.