Dividers; or, What Problem?

stevens dividers

Some of my dividers.  

Sara Bryant of Big Jump Press wrote a breathlessly enthusiastic ode to dividers last month on her blog. Apart from extolling the virtues of comparison measurement, she wondered aloud if she perhaps was becoming a hoarder beause she has six pairs, and if it might be a problem.

My dear Sara, rest assured, you do not have a problem.

stevens divider

My favorite dividers, a 19th century Stevens & Co. Note the unusual, and extremely elegant position of the adjustment screw above the pivot point.

Paring on Glass

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Charles Tomas Jacobi The Printers’ Handbook of Trade Recipes, Hints & Suggestions  (London: Chiswick Press, 1891), 265.

Yes, yes, and yes. Note there is no mention of a litho stone. 18th century paring surfaces seem to generally be marble, I suspect the only reason litho stones became popular was that they were a cheap plentiful source of a flat surface in the late 19th. Save the litho stones for the printers or your beautiful bookbinding photography.

The Movie “Art and Craft”: A Conservator’s Perspective

I recently saw the movie “Art and Craft”, a documentary about the the contemporary forger Mark Landis.  It raises a number of issues that I find interesting, and his forgery of the Mona Lisa is currently on display at Think Coffee (Mercer St. location) in NYC. The entire post is on the American Institute of Conservation’s Blog, link below.

“Conservators have an uneasy relationship with forgery. Often knee-jerk reactions arise: outrage, indignation, feelings of being duped, and sometimes a closet admiration of a particular craft skill. While certainly valid, and generally true, they can be somewhat of a conversation stopper. Deep down, I find myself a bit envious that forgers get so much media attention, and that this attention is generally overwhelmingly sympathetic. Conservation is just as interesting, right?

Some examinations of philosophic aspects forgery within the field of conservation include… Read the rest on AIC’s Conservators Converse Blog

Tips On Making a Delrin Folder

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In this scene from Stanley Kubrick’s classic 2001: A Space Odyssey, the ape is dissatisfied with the properties of natural bone. I suspect he wants a Delrin club. Here is a great explication of the film.

Seriously, animals do tinker with their tools, and so can you. It is an intensely satisfying experience. It gives you a lot of freedom and confidence in designing, executing and using a specific tool for your individual needs. It is interesting to see how tools you have made wear, perform and even may fail in use.

While bone can only be harvested from dead animals, Delrin is mass produced and easily obtained from many suppliers. It is a very hard plastic, originally invented by Du Pont in 1960 to bridge the gap between plastics and metal. There is a dust hazard, as there is for wood, so you should review the MSDS and wear PPE.


1. PLANNING.  It is a good idea to think and experiment a bit with what you like, or don’t like in the folders you are currently using. Monica Holtsclaw has a great introduction to various shaped folders for various purposes. How do you hold it? Do you use both ends? Do you like sharp or rounded angles? Is it for scoring, folding, and/or burnishing? What different operations do you intend to use it for? Making a crude mockup out of binders board glued together for thickness can give a much better sense of what the actual product might feel like and fit your hand. Alternatively, full size scale diagrams are also quite informative. Here is my idea of the ideal shape.

2. ORDERING MATERIALS AND TOOLS.  Obviously, it is easiest to order the Delrin closest to the size you need for the final shape. Mc-Master Carr carries an extensive variety of sizes, but consider yourself warned; their website is more addictive than cheap baggies of high potency heroin. As far as tools, I recommend a 24 tpi hacksaw if you don’t have a bandsaw, a small vice, an 8-inch coarse bastard file with handle, a woodworkers card scraper, a burnisher for putting and keeping the hook on the scraper, and an assortment of 3M sanding sponges for final polishing.

3. ROUGHING OUT. Delrin is easily marked with a soft pencil. Cut it out using a bandsaw or 24tpi hacksaw. The more care you take in cutting evenly and accurately the less time you will need to spend cleaning it up later. A bandsaw makes the roughing out much quicker and I find it easier to get a more accurate cut. Indeed, a bandsaw makes everything — even mistakes and accidents — much quicker.

4. SHAPING. Initial shaping is most easily accomplished by filing. I prefer an 8 inch Nicholson Magicut.  It works well on wood, plastics and laminates. I find the older ones made in USA better made the the newer imported ones. Alternatively any coarse bastard file can be used. Always mount a handle, otherwise the tang can cause serious injury. Grinding or sandpaper tends to produce very deep scratches that are difficult to remove, and I would be nervous about the amount of dust generated. I have experimented a bit with a plane and spokeshave, which kind of worked, but resulted in lots of chatter, unpredictable chipping, and a difficult to clean up surface. It can also be shaped with metal working tools such as a milling machine. And who isn’t looking for a good excuse to buy a table top milling machine?

5. FINISHING.  I find hand scraping (with a woodworkers card scraper) produces the most successful surface finish after filing. You will need to learn how to sharpen it and turn the burr. Scraping is also virtually dust free, since the shavings are a couple of a thousandths of an inch thick and tend not to become airborne. There is some other good advice on finishing Delrin from this thread in the Practical Machinist. In general, the finish of Delrin reflects the tool used. Delrin is very clean and nonabrasive, consequently your tools stay sharp for a very long time. It is a great way to learn about scraping, since it doesn’t have a grain direction to worry about like wood.  A final polish with a progression of 3m sanding sponges, gives it a pretty good finish. The higher the polish the easier it is to clean, and I find the more bone-like it feels.

Delrin is not yet easily available to use in a 3d printer, though I suspect it will be in a couple of months/ years. This could be very cool: one of the most useful and intimate bookbinding tools to be customized and printed on demand. For now, stock reduction is not all that difficult. I’d be interested to hear if anyone has experimented with other plastics for folders.

If you have a bit of experience shaping metal or wood, Delrin is not that different. It is a slightly challenging, but rewarding material to work with hand tools. If making tools is not your cup of tea, you can always purchase a ready to use folder from me, and use this info to tweak it a bit to suit your personal preferences.

I’ve planned a workshop on making Delrin folders. I’ll give it a test drive in a couple of weeks on full time North Bennet Street School bookbinding students. Contact me if you are interested in hosting something similar at your location.


delrin in progress

The Delrin Folder

Mr. McGuire: I just want to say one word to you. Just one word.

Benjamin: Yes, sir.

Mr. McGuire: Are you listening?

Benjamin: Yes, I am.

Mr. McGuire: Plastics.

Benjamin: Exactly how do you mean?

-The Graduate (1967)


Bookbinders have used a variety of materials for folders. Wood, bone, and ivory are common traditional materials. The Excelsior metal folder, made from aluminum bronze, is an oddball patent from 1889. Nylon, bakelite, carbon fiber, Teflon and sometimes even steel have been used more recently.   Today, most bookbinders and book conservators use bone and Teflon. Each material has its advantages.

Earlier this summer, senior rare book conservator at Harvard Library, Alan Puglia, showed me a small spatula for pigment consolidation, which he made out of Delrin. Delrin is a plastic which was invented by Du Pont in 1960. Alan mentioned several advantages of this material, including its low coefficient of friction and rigidity. The material seemed ideal not only for spatulas, but folders.

After making a folder and test driving it for a while, I became a devotee. It is a great material for a folder ( apologies Jim Croft ) combining advantages of both bone and teflon, while not feeling plasticky and soft like Teflon. It can be shaped with hand tools. It is food compliant and impact resistant.  It is used for the stock of the M16 rifle. Du Pont’s informational Delrin booklet.

Delrin is much stiffer than Teflon, and twice as hard, yet has about the same coefficient of friction.  The hardness of Delrin is 120 on the Rockwell R scale, Teflon is 58.  Delrin has a dynamic coefficient of friction of .35, and Teflon about  .2.  More technical specifications of Delrin and Teflon. I had a lot of trouble finding technical specifications on dried bone, possibly because they can vary so much, but this article, “The Mechanical Properties of Bone” , is somewhat useful.  There is a dust hazard in working Delrin, MSDS here. Because of its slipperiness, all adhesives I’ve tried are easily wiped off, even if dried. Delrin is not quite as dense as Teflon. Teflon is 2.2 grams per cubic centimeter, Delrin 1.41 grams per cubic centimeter. Searching for “Bone Density” leads to entirely different results.

Plastics, unlike natural bone, can be made in almost any shape or size. This gives the maker a wide range of possibilities in designing a folder, since there are essentially no limitations on the shape.  I decided on this shape began by examining how I use folders and the various ways I hold them. I notice I often used a Teflon folder flat, as a burnisher, so needed it to be fairly thick and have smoothly rounded corners. Unlike Teflon, Delrin is that a folder can have large gently rounded, non-marring areas and fairly thin, knife like sharp areas that don’t distort like Teflon.

I am a firm believer in the importance of learning how to make and modify your own tools. Next week I will share some DIY tips for making Delrin folders. I’m almost embarrassed how much I enjoy working it by using hand tools. It has no grain, so can be attacked from any angle, and it is very clean, so tools stay sharp a very long time. Like most plastics, it doesn’t have a “mind” of its own but is consistently compliant with the tools and wishes of the maker. Benjamin?





delrin 2




This folder is carefully designed to accomplish all the general uses a bookbinder or conservator has: scoring, folding, turning-in, applying non-marring local pressure, large scale smoothing. The small rounded tip area is shipped slightly blunt, but it can be sharpened if you prefer. Delrin is hard and stiff like bone, but has a coefficient of friction similar to Teflon. It can hold a much thinner and sharper edge than Teflon. It has a nice, non-plasticy feel. I saw, file, scrape and polish these from a solid block of Delrin.

Delrin Folder:  6.5 x 1 x .375 inch. $65.00

“Feeling Small” While Paring Leather

There is a recent New York Times article which describes the difficulties of creating a robot with a sense of touch comparable to a human. One of the links in the article, “Feeling Small: Exploring the Tactile Perception Limits”, contains suprising results. It turns out our fingers are exponentially more sensitive than previous research has indicated. Earlier studies used abrasive paper, while this study used wave-like ridges, which may account for some of the difference in the new findings.

Human fingers, when using “dynamic touch” — sliding across a surface — can distinguish a ridge that is 13 nanometers, which is .013 microns, or about .0000005 of an inch. For comparison, the thickness of a sheet of standard copy paper is a mountainous .004 of an inch thick. The average particle size of green chromium oxide stropping compound is .5 micron, which produces a mirror finish on steel.

My mind is blown. Should I be able to feel the individual fibers on a Japanese tissue paper repair? Will I ever be able to pare leather smoothly enough?

A Book and a Model of a Book

model and book

A two image gif: a model of an 18th century French binding and a real 18th century French Binding

Conservators often make models of bindings in order to understand how materials, structures, and techniques interact. Models are different from a facsimile or pastiche bindings: they are not intended to look like an old binding, but are made as closely as possible to replicate an historic structure. Making models helps conservators understand subtleties and procedures of construction, and aids in determining what physical evidence is essential to preserve. While acknowledging a model’s new materials, conservators can also use them as a mock-up to test treatment options.

The model above was made by following the technical descriptions in Diderot, Dudin, and Gauffencourt. (1)  How does this gif inform our understanding of the relationship between the model and historic binding?  How can the lacuna between them be interpreted? In this gif, the model simultaneously bursts out of the historic binding as the binding disappears into the model, possibly analogous to our conceptual understanding of the two.


1. Denis Diderot and Jean le Rond d’Alembert Encylopedié ou Dictionnaire Raisonne des Sciences, des Arts et des Métiers, Paris, 1751-1780; René Martin Dudin L’Art du Relieur-Doreur de Livres, Paris: Saillant & Nyon, 1772; Jean-Vincent Capronnier de Gauffecourt Traité de la Relieure des Livres (originally 1737) trans. by Claude Benaiteau, Austin: W. Thomas Taylor, 1987.

Added 17 Sept 2014:

Model and book