Managing a Slide Rule Collection


Any storage system that works is a good storage system.  I have heard of successful storage systems using library card-catalog drawers and blueprint storage units.  In my opinion, the ideal slide rule storage cabinet has drawers 14-1/2 to 16 inches from front to back and 3 to 3-1/2 inches deep.  Drawer width is not critical.  14-1/2 inches accommodates ten-inch rules with extra-long over-range extensions such as the Relay/Ricoh model 157; 3 inches deep allows you to place cases on edge in a single layer.  A great thing for slide rule collectors is the Iris Six-Drawer Storage System (Iris part number IRS121912).  It's an all-plastic unit with drawers 15 inches from front to back and 3-1/4 inches deep.  With casters, the overall size of each unit is 12.75 x 16.25 x 26.75 inches.  Without casters—which is the way most collectors use them—25 inches tall.  Each drawer can hold a dozen Versalog cases or about 20 K&E cases or up to 40 five-inch cases.  I have about 300 slide rule cases stored comfortably in three units.  Iris Storage Units cost about $35 each and are available from Staples, Office Depot and other office supply stores.

Whoops.  Since I wrote the above, Iris seems to have discontinued the entire line of storage units of which IRS121912 was part.  Iris has replaced them with similar looking units which are only about 14 inches deep overall--not deep enough for a ten-inch slide rule.  I was able to find a  model 121912 through the Internet for an exorbitant $60 (including shipping) in August 2005.

Now that you have a place to store your cases, you have to decide if you are going to store your slide rules in their cases.   Personally, I don’t.  I like to have immediate access to all my rules.  The delay in figuring our which drawer the rule I need is in, finding the rule within that drawer and removing it from its case is intolerable.  So I keep nearly all my rules displayed on pegboard in my office.  (That’s why my collection is limited to about 300 rules.)

There is another advantage to storing rules out of their cases:  Many rules become yellowed in their cases.  It is my experience that storage in the open air invariably eliminates that yellowing in a few months without any effort on my part.  If you decide to keep your rules in their cases, I suggest you make exceptions for extremely yellowed rules; store them in plastic bags next to their cases.

I store my slide rules on my walls and their cases and boxes in Iris units; instructions are with the box or case.  The cases are in plastic bags with the end left open.  I’m nervous about storing leather in plastic bags but the bag protects the case from abrasion and keeps an identifying label with the case.  I use common zip-lock polyethylene bags.  Almost any size you want is available in quantity on the Internet.  I find 3 x 8, 3 x 15, 4 x 16 and 6 x 9 inches to be useful.  True archivists store most things in Mylar bags; you can find Mylar bags for sale on the Internet from library and museum supply sources.

Record Keeping

A computer spreadsheet is a good way to keep track of your collection.  Here are the fields I suggest:

Information relating to model of rule

Information relating to specimen Front Scales:  There isn't any standard convention for listing slide rule scales.  The scale names (C, CI, etc.) are reasonably standard and most collectors list scales in order from top to bottom but there is no agreement on how to separate the scale names and how to indicate which scales are on the stators and which are on the slide.  Some collectors list the scale names with spaces but no punctuation between them but my opinion is that the redundancy of punctuation and a space is important.  Besides, some scale names ("SecT ST" on the back of the Versalog, for example) actually contain spaces.  I enclose the names of the scales on the slide in brackets--thus the front scales on a Versalog are LL0, LL/0, K, DF [CF, CIF, CI, C] D, R1, R2, L.

By the way, which is the front side of a duplex slide rule?  My convention is the side with the shorter stator up.  Others use the side with the maker's name or the side with the A and B scales.  Users of the latter two conventions have to indicate the shorter stator separately.  All systems run into problems with exceptional rules.  (What do you when both stators are the same length?  What if there is no maker's name or it's on the edge?  What if there are no A and B scales or if there are A and B scales on both sides of the rule?)

Market Value is important if you are as old as I am.  Your heirs need to know.  I trust you have told them generally how to dispose of your collection.

Acquisition number:  Give each item you acquire a serial number and mark all its accessories with that number.  One way to do this is to buy four sets of consecutively numbered gummed labels.  Put one on the back of the slide rule, others on slips of paper with the case, box, instructions, etc.  It’s ok to put gummed labels on your slide rules but NOT on paper or leather items.

I use pretty much the system outlined above but I store the data in an Access database--actually three linked Access databases—a model database, a specimen database and a vendor database.  (This is ‘way more complicated than necessary.)  The principal benefit in using a database is its “report” capability.  My database prints separate labels to be kept with the slide rule, the case, the box, and the instructions.  It also prints a full page report on each rule—including a picture of the specimen—which I collect in a loose-leaf notebook.  (Sample page shown at right.)  Various summaries of the entire collection are available, too.

All-in-all, I don’t recommend a database in preference to a spreadsheet.  Microsoft Access is buggy and I had to find “work-arounds” for several things.  It’s not as convenient as a spreadsheet--for example, one could sort a spreadsheet on market value with a couple of key clicks but I’d have to figure out how to write a program to do that in a database.  It is nice that the database assigns an acquisition number automatically and puts that number on all the labels but I have to write it by hand on the gummed label I put on the rule—which I sometimes forget to do.

It is not necessary to keep your records on your own computer.  Some collectors post pictures and information about all their rules on their Internet Personal Web Pages.


You ought to have pictures of every slide rule in your collection.  You’ll need them if you have to file an insurance claim.  And exchanging digital pictures is the standard way for collectors to communicate on the Internet.  You can arrange your spreadsheet or database inventory system so that clicking on the "Picture" field opens a picture of the slide rule.

Flatbed scanners are the best way for slide rule collectors to acquire pictures of their rules.  Since a slide rule sits slightly above the glass surface—not in contact with it—the scanner needs great depth of field in order to produce a sharp image.  “Charge-coupled-device” (CCD) scanners have much better depth of field than do “contact-image-sensor” (CIS) scanners and should be your only choice.  “Legal-size” scanners will scan the full length of a ten-inch slide rule; “letter-size” won’t.  When purchasing a new scanner in 2004, the only companies I could find that marketed reasonably-priced legal-size CCD flatbed scanners were Microtek and Umax.  I bought a Microtek Scanmaker X12USL; it has served me very well.

How about using a camera instead of a scanner?  The best slide rule pictures I have ever seen were taken by Herman van Herwijnen with a camera on a permanently set-up copystand.  He avoided distortion and improved resolution by photographing his rules in sections no longer than about 6 inches.  The camera and copystand technique handles specular reflection and background rendition much better than flatbed scanners do.  However, flatbed scanners come out 'way ahead on convenience and resolution.  (A quick, "back of the envelope," calculation indicates that it would take about a 39 megapixel digital camera to equal the resolution of a flatbed scanner at 600 dpi.)

What resolution should you use?  It depends upon what you're going to use the pictures for.  My friend Atsushi Tomzawa scans his slide rules at 300 dpi and his pictures show incredible detail--much better than is visible to the naked eye.  However, his picture are typically 3500 pixels wide and his files are very large.  I want the pictures on this web site to not be much wider than typical computer screens (say 1000 pixels or less) and to have small files (50kB or less) so they will transmit quickly.  (I had only a dial-up connection when I started collecting slide rules.)  The best compromise between resolution and size seems to be to scan at 150 ppi, reduce the picture size by 50%, and convert to a jpg file with fairly high compression.  (That's my current practice but many SRTC pictures were taken before I settled on it.)

For my personal collection I scan the leftmost 7 inches of each rule at 600 dpi with a gray scale.  That produces a nice 1:1 black and white picture on each inventory page.

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