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

Bone Folders: Our Nearest and Dearest Friend

John Farleigh, in a chapter about Sidney Cockerell from his book The Creative Craftsman, gives a particularly observant account of the relationship between a book binder and a bone folder.

“Another man is at work putting down a leather joint on the inside of a bound book, using a folder with quick, skillful movements reminiscent of the grooming of a horse.  The folder, a small ivory instrument that has to the ordinary eye the appearance of a paper-knife, is in fact a most important tool to the binder. Its shape is fashioned with great care and according to the habits of the craftsman himself. Every facet of its surface, every curve and subtlety of its edge, is known and used for a purpose, and no craftsman will readily part with this tool. This particular craftsman tells us, as he would talk of the loss of his nearest and dearest friend, that he has just broken his folder—an extra thick piece of vellum needing rather more pressure than usual found a weakness in the ivory—and we are shown the sad remains”

The finest bone folders on earth are being made today by Jim Croft, pictured below.  He processes wild deer and elk bones with his teeth and hands.  He also offers intensive workshops on making books from raw materials: toolmaking, processing fiber, papermaking, and wooden board binding with clasps. Below he is wearing his signature bone folder vest.  Check out his website,, or email him to purchase raw or finished folders: traditionalhand AT



John Farleigh  The Creative Craftsman (London: G Bell and Sons, 1950) 92.

Big Bamboo Folders

Finally, the perfectly shaped bamboo folder?!?

Hand tools, in particular, need to be tested and evaluated by using them. A poor design aspect quickly becomes apparent. The simpler the tool, the more critical each aspect is. And tools don’t get much simpler than a smooth bone or wood folder.

Folders are used by bookbinders to fold paper, smooth covering materials, shape leather, and evenly adhere various covering materials. Bone, ivory, teflon, and sometimes wood, are the usual materials for western style folders.  Teflon has an extremely low coefficient of friction, making it ideal when you want to slide the tool over a surface that you don’t want to mark. Bone has a density and feels—for lack of a better term—traditional. I especially recommend the higher quality ones made by Jim Croft from wild elk and deer. Bamboo has been used in the east for many purposes. It has a higher coefficient of friction to it which makes it useful for pulling a covering material. A light touch or protective covering sheet must be used if marking is suspected to be a problem.

Bone folders —like most tools— have become smaller over time (technically known as ‘dinkification’).  Evidence from the eighteenth century France suggests folders, commonly wood at this time, may have been 12 -18 inches long.  The bamboo folders I’ve been experimenting with are a more modest  9-10 inches, though.

I keep tweaking and altering small aspects of these folders with successive iterations. The long straight sides can be used like a case folder, for turning- in. The flat areas at the pointed end are useful for pressing and forming headcaps. The angled tip useful in box making. The rounded end handy when defining joints or adhering board edges. The relatively long length makes them more comfortable to hold. This is the theory, at least. Quite likely there is no ideal shape, but what we prefer and use changes with our working habits. Or we choose tools to break us out of habituated working methods.

Bamboo is quite easy to shape and fun to work with.  I’ve written up some tips on working with it in an earlier post. If you discover the perfect shape, please let me know. I’ve already started on the next one, which will certainly be the absolutely most perfect….

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