A brief history of the slide rules

The first slide ruler was produced at the factory in Geroldsgrün in north Bavaria, founded by Lothar von Faber in 1861 to mark the centenary of the business based in Stein near Nuremberg which by then had already gained an international reputation.

The page reproduced from the 1896 company catalogue (price list) shows examples of rulers and straight-edges and also the two oldest models of slide rule: No. 350 made of box wood with the “Mannheim” scales and a glass cursor, and below it No. 360, also made of box wood but with celluloid scales. Both models are only partly depicted, the left-hand half of No. 350 and the right-hand half of No. 360.

A later catalogue, dated 1912, offered a wide range of nearly a hundred different rulers, set squares and T squares made of wood, and then 20 models of slide rule of high quality and precision, made of pear wood (ideally suited to the task) with celluloid scales.

The favourable development since the early days was sadly interrupted by the Great War. The post-war depression and subsequent hyperinflation were very difficult times for the very specialized range produced in Geroldsgrün.

Slide rules were still unfamiliar to most people and used only by a limited circle of engineers and technicians, rarely by businessmen.

It was therefore not possible to introduce rationalized mass production. However, additional models for specific occupations and types of calculation were produced in collaboration with experts. There were now special-purpose slide rules for foresters and timber merchants and for reinforced concrete work.

A period of rapid growth began in about 1931. The slide rule was now an important tool for engineers and in widespread use. In 1935 a new model (“System Darmstadt”) was brought out, based on the ideas of Prof. Alwin Walther of the Darmstadt Polytechnic and with his cooperation; for many years this assured an excellent market position for Faber-Castell. The Model 1/54 slide rule was made from pear wood with celluloid scales and became known as the engineers’ rule. By 1940 there were more than 50 different models for technical and business calculations and also for special applications. Production was very much restricted during the war years, and only a limited number manufactured for civilian use, while certain models were required by the armed forces and the government, for which the raw materials were made available.

New methods of producing the slide rules were introduced in 1950. Increasingly, plastic models became available to supplement the proven range of wooden slide rules. To start with, the various lengths were cut from sheet material, but later injection moulding was used, which significantly speeded up the initial stages of production. The use of plastics made it much simpler to produce double-sided slide rules, a costly process with wooden versions where the scales had to be aligned individually.

37 patents had been granted (at first by the German Empire and later the Federal Republic) and 95 designs registered, which illustrates how important the slide-rule business was for Faber-Castell.

The double-sided slide rules became increasingly popular. The best-known products in the final years were the ‘D’ model for schools and especially the Novo-Duplex, which some collectors still describe on web sites as the best slide rule in the world.

In 1974 an electronic model was developed at Geroldsgrün. This combined a pocket calculator with a traditional slide rule; however, this series, designated TR1 – TR3, could not compete with cheap mass-produced products from the Far East.

Slide rules in their original form and function now increasingly lost their importance, in schools and at work. Sales fell off drastically and in 1975 the market dried up.

Remaining quantities of slide rulers are still available at Faber-Castell.
For more information please call: 0911 - 9965 5421 or contact info@Faber-Castell.de