Friday, October 23, 2020

Faber 1/54 (and how to take care of your slide rule)

 The number is on the box.

Again a fine and solid instrument made by A.W. Faber Castell. Around 1935 they moved from the 3-digit type-numbers to a 'slash'-code system and that year also introduced a 'Darmstadt' slide rule as the 1/54.

This slide rule was a bit yellow with ageing and also seized-up, but otherwise fine. Complete with no damage, chips or worn spots and still straight as a rule. The date-codes stamped in the wood of the base at either end of the slide rule show it was manufactured in Germany in May 1941. Date-codes '41' at left, '5' at the right end. (There's also a 'D' stamped in the left end-face of the rule, meaning unknown so far.)

Brief instructions on the back (label 'K8d'), and at both ends a transparent celluloid section with the gauge-lines for the Log-Log scales on the back of the tongue. The goniometric scales have been moved to the front edge of the scale and the linear scale to the far edge. At the spot where there'd be a linear scale on a 'conventional' Rietz, there is the Pythogarean scale P - ergo a 'System Darmstadt' slide rule.

Even inside the well, there is a cm-scale extension. Every surface serves a purpose. This also means there is a complex 3-sided cursor. This is constructed from aluminium brackets holding Plexiglas plates. (It is a German slide rule, so Plexiglas, in English this'd be called Perspex and in North America Lucite.)

The slide rule was a lucky find on a German auction-site - the instruction booklet to go with it was also sourced from Germany (albeit much less of a bargain...).

Much like wanting to have the vintage items functional, there is some satisfaction in completing an item with the correct paperwork - to come a bit closer to experiencing the product as it would have been purchased originally. This booklet is reasonably correct for this rule - second printing, dated February 1945. Had not expected that by that time there would still be materials for the printing (with colours) of a slide rule instruction manual. Perhaps deemed important - but I'd think the situation had become rather dire in Germany by then. (This particular rule is more likely to have had a first printing of this edition of the booklet, d.00001 was from April 1941 - but to hold out for a first printing 'd be pushing things a bit too far perhaps.)

The illustrations match the slide rule, these are definitely the instructions to study :)

The text is of course thoroughly informative, exact and precise. Likely because I'm not a native-speaker of German, but this made its sudden use of the word 'ungeheuer' unexpected. (Bottom paragraph of the page 11.)

The scale R is indeed 'enormously' useful, but as non-native reader I read it as 'monstrously' useful - 'Ungeheuer' as noun also means 'monster'. To a native speaker the phrase very likely would not be remarkable at all, but it made me smile :)

There are extensive instructions with examples on how to get the best use out of this precision instrument. Very importantly, it also contains a paragraph on the maintenance of the slide-rule. The "How should one treat his Castell slide rule?" paragraph.

Obviously one should keep it out of direct sunlight and not expose it to large variations in temperature or humidity. For cleaning the scales, the celluloid surface can be wiped with petroleum or white spirit. (Never with alcohol! This dissolves the celluloid - indeed it does, rather rapidly too.)

An alternative method given for cleaning the celluloid scales is a soft eraser - that is excellent advice and it worked wonders on the old, yellowed surface. The white stripe across the rule in the picture below shows the effect of only a brief application of the eraser - with some time spent going over all surfaces the whole sliderule becomes much cleaner again.

Further advice is to apply a little vaseline to the sliding surfaces of the tongue. This does indeed help to revive a long dried-out rule. In this case it also needed a little (little!) talcum to reduce the stick-slip effect that remained, but vaseline is I think generally good advice for a wooden slide rule.

Again a functional instrument! Obsolete of course, but fascinatingly ingenious and it will be entertaining to discover from the instructions how to work it.


  1. Nice slide rule.
    I've used a soft eraser to clean them at times.

    1. Yes, it does work well to clean the celluloid surface - perhaps an instance of what once was 'common knowledge' and now obsolete.

  2. Isn't it likely that the 'D' stamped in the left end-face of the rule stands for Darmstadt?

    For what it's worth, as a lifelong North American, I've heard both "Plexiglass" and "Lucite," but "Plexiglass" much more often.

    1. Ha! Of course :-) Could imagine when stocks are stacked in the factory, makes it possible to tell Rietz and Darmstadt stocks apart. Was thinking too difficult (D&P used such letters for factory designations).

      We'll definitely settle on Plexiglass then :) Every company that invented a PMMA gave it a tradename, hadn't realised that R&H actually also sold into US at the time.

    2. Hmm, perhaps not D for Darmstadt. On is shown a 1942 1/54 that has an M on the end-face... Hmmm...