Of all the materials that are suitable for the fashioning of insulators, one of the most unlikely was chosen in San Francisco. The year was about 1900. The material was wood. The reason was far reaching and somewhat complicated. Therein lies the fascination.

Going back to what we know about the requirements of insulators, we find that the finished product must be a non-conductor of electricity, non-hygroscopic, structurally sound, and dimensionally stable. Not only must it have these qualities, but, it must retain them while giving many years of service in all kinds of weather. Glass, ceramic, and rubber were, as now, ideally suited for the task. Why then wood?

As the story was related to me, the insulators were to carry a high voltage line which was the supply of power for electric streetcars in San Francisco. The total number required was very limited. The glassmakers (even those in San Francisco) were too busy to bother with such a small order. The state of the art in the ceramic industry (far behind that of today) simply couldn't produce a qualified product. Rubber was far too expensive for almost anything in those days, especially insulators.

In spite of these setbacks, the problem was solved, as problems usually are when ingenuity prevails. The solution came when it was decided that, rather than mold the insulators they would machine them from wood. The name of this wood is "LIGNUM VITAE". It has as its attributes these qualities. It is a non-conductor of electricity. It is extremely dense, thus it possesses structural integrity. It is very oily, thus the finished insulators would shed water very nicely.

Obtaining LIGNUM VITAE was a simple matter as San Francisco was (as now) a stopping place for trade ships from all over the world, especially the South Seas, where LIGNUM VITAE is grown.

Although these wooden insulators are being replaced, many are still in service and doing a good job carrying the 600 volt line for the San Francisco streetcar system today.

I have in my possession a retired LIGNUM VITAE insulator with a hearty thanks to Gale Blosser of California, from whom I received it through a happy trade. Statistically it is 4" high, 3" in diameter, 1 pound 8 ounces in weight, and is threaded to fit the standard peg.

We have received so many letters lately asking about these insulators, that I felt this article by Frank Saccoman, sent in by Gary Cranfill, would be of interest. I would like to add that this was written a few years back, and since then most of the insulators are down, and the ones left are on metal poles.

A word about the above pictured woods. The two cable tops are identical, except the dark one has been cleaned and polished and has no inner skirt, while the light colored one has a very short inner skirt and is weathered. The round domed wood was used on corners, and there weren't as many made. The price of these runs from $15.00 to $25.00 here on the West Coast, depending on condition. I predict they will go up in price in future years.

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