Category: tools

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How to Strop a Knife

Stropping is a motion which pulls the cutting edge away from a substrate—leather, paper, wood, etc.—perpendicular to the cutting edge, with or without additional compounds. Stropping not only produces a very sharp final edge after sharpening, but it is an easy way to renew a slightly dull edge without having to go through the entire resharpening process. I tend to strop my knives whenever they feel a bit dull, or I have to apply excess pressure when using it, or when edge paring very thin leather.  I find stropping the quickest, easiest way to keep the knives used for leather paring sharp.

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TECHNIQUE

The above video illustrates the technique I use in stropping, using the materials I will discuss below. I strop all the knives I sell using this method, and use it to keep my own knives in shape. There are two key aspects. First, always draw the blade away from the cutting edge to avoid digging into the leather, which is sometimes called a “trailing stroke”.  Second, it is paramount to hold the knife at the exact bevel angle it was made, and keep this angle consistant throughout the stroke. If you raise the angle, even a few degrees, the cutting angle will rapidly become too obtuse and you will have to resharpen or possibly even regrind it. Similarly, the back needs to be kept flat.

I find a strop that is 12-15 inch long and 2 or 3 inches wide ideal. If it is shorter you will have to reposition the knife an inordinate number of times, which slows the process and may introduce more errors.  If the strop is too long it is difficult to maintain a consistent angle on the blade throughout the length of the stroke. If the knife is slightly wider than your strop, just angle it a bit so it fits.

I count the number of strokes I do on each side to keep them even, 12-15 times on each side is a reasonable starting place.  If the knife is still not sharp, strop some more. If it still is not cutting well, it may need to be resharpened or reground. Although you are *just* rubbing a knife on a piece of leather, don’t be fooled that you are not doing anything: all the black marks are metal that have come off the blade.

Eventually, however, even careful stropping will gradually create an obtuse cutting edge. It may look sharp and have a mirror shine, but it will need to be resharpened using your preferred sharpening system.

MATERIAL FOR THE STROP

I prefer a two stage stropping. First I strop on the flesh side of horsebutt, which is dressed with a .5 micron green honing compound.  Horsebutt strops available here. Then I do a secondary, final, stropping on undressed flesh side of calf. This is why I flip the strop over in the video. I find it gives an excellent final “bite” when paring leather, though some people prefer just the hair side of the horse butt, others skip this step completly.  Other substrates for strops are wood, MDF, binders board, cowhide, mat board, etc. Anything firm and  flat can work, although a material that compresses too much will round over the cutting edge more quickly.  I prefer horsebutt over cowhide because the surface lasts longer, it is firmer, and it is a traditional material for high quality strops.

I generally use the strop on a hard flat surface but some people mount them to wood or other flat material.  Since I use mine two sided I find it easer to just flip it over.  The speed that you strop at does not seem to make much of a difference, as long as a consistent angle is maintained. There are also a variety of leather belts and discs to attach to power machinery, but I find it is too easy to round an edge using these, and it is not really much of a time savings since stropping does not take much time by hand.

COMPOUNDS FOR THE STROP

My preferred stropping compound is a .5 micron green chromium oxide buffing compound. I now sell a convenient 1 oz. bars of them, and my sharpening system also now comes with them. I like the edge this compound gives to the knife, and it does remove metal fairly quickly. Chromoglanz is another popular option among bookbinders, though I don’t know how precisely the abrasive is sized, and I personally don’t like the way it feels when you are stropping—it is very slippery. It seems to be better at polishing than establishing a cutting edge. There are other types of powders and honing compounds available as well, jewelry suppliers often have a wide variety. Quarter and half micron diamond paste is an expensive, but addictively fast cutting strop dressing and a real joy to use.

Careful stropping can keep an edge tool cutting well for a long time.

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Rare Book School’s Jacques Ploschek Bindery Collection and Leo Sewing Support Clamps

If all printed information the world were somehow destroyed, but Rare Book School’s (RBS) collection of books, illustrations, material samples, ephemera, tools and equipment somehow spared, could our bibliographic heritage be reconstructed? Would it matter? Without any artifacts to study, would these obsolete technologies have any bearing in future organization and dissemination of information? What could they tell us about the past? I found myself wondering questions such as these as I was given a tour through the collections of RBS, which seemed like a kind of seed bank that could repopulate the world of books after an apocalypse.

I should have spent the afternoon examining eighteenth century bindings.  Instead, part of the collection, some bookbinding tools, caught my eye. Quite likely bibliographers may dismiss the tools of bookbinding as unimportant, or even unrelated to books. But what is the physical book other than an assemblage of materials, organized by structure and technique, formed by tools?

Barbara Heritage, Assistant Director and Curator of Collections, provides some background on this collection. “Thanks to the good offices of Dan Dwyer (Johnnycake Books, Inc of Salisbury, CT), RBS was able to acquire the bindery of Jacques Ploschek (1919–2009) through his executrix and step-daughter, Tania Poliakoff.  The gift, appraised at $25,000, includes a large collection of finishing tools in excellent condition, including c.450 decorative hand stamps, pallets, gouges and seven decorative rolls and fillets, as well as a sewing frame, backing press, plough, and group of lying and finishing presses.  Ploschek studied under the binder Charlotte Ullman, whose tools can be found among this wonderful addition to our teaching collections.”

In particular were an unusual form of sewing hooks and keys, so remote from their historical origins that they seem to deserve a new name— sewing support clamps?

Fig. 1. A Pair of Leo Sewing Support Clamps. RBS’s Jacques Ploschek Bindery Collection.

These sewing support clamps are designed to fit into German style sewing frames, which have a slotted upper crossbar (cantilevered or not) which usually contains hooks which can slide horizontally into position, and lowered or raised vertically by a wing nut, similar to the one on the far right.  The flat area, stamped “LEO”, serves to prevent the entire hook or clamp from twisting as the wing nut is adjusted. Although the sewing frame they are associated with had a gated front, I imagine they could fit into and function in a standard slotted version. Another possibility may be that the clamp on the right  (and in Fig. 3) is made to fit into the upper position of an English style sewing frame, which typically has a round upper crossbar.

Fig. 2. The Leo clamp in the frame. RBS’s Jacques Ploschek Bindery Collection.

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Fig. 3. Lovely file work on the lower (?) clamp. RBS’s Jacques Ploschek Bindery Collection.

These clamps are designed for tapes or vellum, quite possibly for account or blank book work given their width.  They are presumably German, given their design based on a hook, and seem likely to have been invented by the Stuttgart bookbinder Wilhelm Leo, who in the late nineteenth century invented an unknown number of bookbinding tools and machines.

Four of Leo’s innovations, with woodcuts, are featured in Zaehnsdorf’s 6th ed., Art of Bookbinding, 1903: two types of mechanical  marbling machines, a set of marbling supplies for bookbinders, and perhaps the most well known, his finishing press. Zaehnsdorf notes the complete set of marbling supplies is particularly invaluable to the small, country bookbinder. None of these illustrations, or textual descriptions, are in the the first (1880) edition of Zaehnsdorf. I haven’t been able to check the other editions. No other manufacturer receives four separate mentions; endorsement by Zaehnsdorf is high praise indeed.

Fig. 4. The Leo Mechanical Marbler. Zaehensdorf, 6th ed., The Art of Bookbinding, 1903, 75.

Zaehensdorf describes the function: the top roller (or rollers, one version has more) is inked, and the spring pressure transfers it to the lower roller which contains an embossed pattern. This is then transferred onto the book edges. Currently, I am unaware of specific examples produced by this machine, but the ‘cobweb’ style pattern on the roller is seen on German books from around this time.

Fig. 5. The Leo Finishing Press. Zaehensdorf, 6th ed., The Art of Bookbinding, 1903, 122.

The Leo finishing press is more well known, with an updated version manufactured in the US in the 1990’s, known as the Jordan-Dehoff finishing press. This version swings out of the way, under a workbench when not in use. Several binders I know who have them swear by them. When looking at the above illustration under magnification, it appears the Leo press has a fore edge shelf, which Jordan-Dehoff version lacks.  There are also some striking visual resemblances between this fixture and dictionary holders of the time.  These sewing support clamps and the finishing press do reveal several commonalities: a single screw, easy adjustability, intelligent design, and are well made. Additionally, the ball head on Leo’s press is a very early precursor to the ball head now standard on tripods for photography. Book as camera— fodder for the book artist or poet, I suppose….