The Pasted Strop – part 4

In part 1 of the series, it was shown that edge-trailing and edge-leading strokes on a hard, flat abrasive hone lead to entirely different processes for apex formation and refinement.  The edge trailing (stropping) stroke allows a keener apex to form by avoiding the micro-chipping that occurs in edge-leading strokes.   However, the edge-trailing stroke can lead to the formation of a foil-burr while the micro-chipping that characterizes an edge-leading stroke generally limits the formation of a foil-burr.

In part 2 of the series, it was demonstrated that the use of a compressible substrate (a strop) produces  micro-convexity and can avoid the formation of the foil-burr that is usually produced when performing edge-trailing strokes on an in-compressible substrate.  This micro-convexity typically improves keenness and apex uniformity.

In part 3 of the series, it was shown that the amount of micro-convexity is determined primarily by the choice of strop material.  It was also demonstrated that partial or incomplete micro-convexing of the apex can produce a foil-burr (as in the case of 0.25 micron diamond on leather, for example).  It was also observed that the effect of stropping is rapid (requiring only a few strokes) and that further stropping (up to hundreds of strokes) has minimal additional impact.

 

In this edition of the series, the role of abrasive size (grit) is examined.  In particular, it will be shown why stropping a straight razor with metal polish on denim is so effective, despite being seemingly contrary to the common “wisdom” of internet experts.

Some time ago, I purchased a stick of “Thiers Issard Pate a Rasoir” stropping compound.  This white crayon-like stick of aluminum oxide abrasive in a waxy carrier is fairly well regarded among people who have used it on their straight razors.  The product is usually described by retailers as being “10,000 grit” (abrasive particles in the vicinity of one micron).  When analyzed by SEM, the abrasive is clearly much coarser than 10k grit – there were many particles in the ten micron range and I found one as large as 100 micron.

 

TI_white_rasoir_06

Thiers Issard Pate a Rasoir honing compound.  Particles range from sub-micron up to tens of microns in diameter.

 

Despite being far coarser than advertised, I applied the product to a hanging strip of denim and worked it into the fabric with the spine of a razor.  The razor was honed on a progression of Shapton glass plates to 16k (producing a triangular bevel) and then stropped for 30 laps on the loaded denim.  This razor has a 16.5 degree innate bevel angle and after stropping, the angle measured 20 microns from the apex has increased just one degree.  This increase in angle is a result of a very slight bevel convexity resulting from the use of a hanging strop.

 

TI_white_30denm_04

Cross section view following the Thiers Issard white pasted denim strop.  The included angle has increased by one degree (from 16.5 degree) indicating a slightly convex bevel has formed.

 

The induced micro-convexity is evident where the angle is measured at 3 microns from the apex and  observed to increase by 8 degrees from the innate angle.  Micro-convexity is produced independently of the larger scale bevel convexity.  The apex is relatively clean with minimal burring and keenness sufficient for shaving.

TI_white_30denm_02

Cross section view following the Thiers Issard white pasted denim strop. The apex is smooth and regular with an edge width of approximately 100nm.

 

When comparing the effect of different abrasives, we need to minimize the impact of other variables.  We can use the same strop material, and the same length and number of strokes; however, the downward pressure is a challenging variable to control.  The three images below were presented in Simple Straight Razor Honing and demonstrate that downward pressure plays a determining role in the amount of micro-convexity produced on a particular strop.

 

GEN_16k_Flitz_light_03

Cross-section view of the straight razor stropped on the Flitz polish loaded denim strop with relatively light force (less than 50 grams equivalent). The near apex bevel angle has increased by less than 4 degrees

 

GEN_6kET_FlitzDen_03

Cross-section view of the straight razor stropped on the Flitz polish loaded denim strop with medium force (estimated to be 100-150 grams equivalent). The near apex bevel angle has increased by 6.5 degrees.

 

GEN_flitz_heavy_03

Cross-section view of the straight razor stropped on the Flitz polish loaded denim strop with relatively heavy force (estimated to be 300-400 grams equivalent). The near apex bevel angle has increased by 11 degrees.

 

In the experiments that follow, I have made every effort to maintain the pressure in the normal range (100-150 gram equivalent), and repeated the tests with different razors to confirm the observed trends are repeatable.

Over the past two years, I have tested a variety of other metal polishes on denim strops (Mother’s, Flitz, Simichrome, Wenol, Pikal to name a few) and all have performed and analyzed similarly.    The example below shows a blade honed with the Shapton 16k and then stropped 30 laps on a Mother’s Mag polish loaded strip of denim.  The result is nearly indistinguishable from that produced by the TI white razor paste.

 

mothers_mag_04

SEM image of Mother’s Mag and Aluminum Polish. Particles range from sub-micron up to tens of microns in diameter.

 

GNV_16k_HdenMM_01

Edge view SEM image of a straight razor honed with a  Shapton 16k followed by 30 laps on denim loaded with Mother’s Mag polish.

 

GNV_16k_HdenMM_04

Cross-section SEM view of a straight razor honed with a Shapton 16k followed by 30 laps on denim loaded with Mother’s Mag polish.

 

 

The are two obvious questions that arise from the results above. First, why is the result so insensitive to the choice of stropping compound? and second, how is such a keen edge produced by such coarse abrasive?  To provide some insight, I compared the effect of denim strops loaded with diamond abrasive ranging from 0.1 microns up to 15 microns.

Prior to performing this particular experiment, I had two experiences with very surprising results.  The first involved the use of the Thiers Issard razor paste. After using the Thiers Issard pasted strop for 30 or 40 razors, the strop had become glazed and seemed to be less effective than when new. Rather than making a new strop, which is now my habit, I “re-loaded” that strop by rubbing the abrasive “crayon” lightly over the stropping area and working it in with the spine of a razor, as usual, and then stropped a C135 steel Thiers Issard razor, one that I have used regularly for several years. After 30 laps on the TI-pasted denim, I proceeded to strop the razor on the 0.25 diamond sprayed leather and the stropping both felt and sounded rough. Inspection with a loupe and feeling with my thumbpad revealed that the edge of the edge had been broken away at a relatively coarse level.  So much damage had been done that reseting the bevel required a substantial amount of steel to be removed, as much as is usually required when restoring a vintage razor.  SEM imaging  had shown that the paste contains particles of up to 100 microns, and these are more than capable of destroying the edge of a straight razor, but had not done so prior to re-loading the strop.

The second surprising result came when I began testing  coarse diamond loaded strops.  I purchased a set of inexpensive diamond pastes (the ones that cost one dollar each, shipped from China).  I analyzed several of them by SEM and found that the size distribution was excellent, in fact better than some products that had cost me 50 times as much.

 

badak_10_01

SEM image of Badak 10 micron diamond paste.

 

I loaded a strip of denim with the 10 micron diamond paste and stropped a razor honed to the 8k level, and was astonished to find that the strop had essentially no effect.

 

Sh8k_Badak10_03

Cross-section SEM image of a razor honed with a Shapton 8k hone and then stropped on a denim strop loaded with 10 micron Badak diamond paste.  The abrasive produces no observable effect.

 

It is challenging to quantify the concentration of diamond in a product, particularly in an oil-based paste.  The obvious hypothesis is that this product may have good size distribution, but low concentration.  Moving forward, I acquired a set of “scientific” quality, high concentration, poly-diamond sprays with sizes ranging from 100nm to 15 microns.

In the set of images that follow, a razor was honed with Shapton glass stones up to the 16k level to produce a keen triangular apex, one that would easily demonstrate the effect of stropping – the induced micro-convexity and any effect on the apex.  The razor was then stropped, 30 laps, on a strip of hanging denim loaded with the particular sized diamond abrasive.  As a control, the effect of clean (no diamond) denim is also shown.

 

GEN_16k_control_01

Edge view SEM image of the starting point in this experiment, the blade honed to the Shapton 16k with edge-leading strokes.

 

GEN_16k_control_02

Cross-section view SEM image of the starting point in this experiment, the blade honed to the Shapton 16k with edge-leading strokes.  The razor has triangular apex with 16.5 degree bevel angle.

 

GEN_16k_clean_denim_03

Stropping on clean denim demonstrates the usual effect, microchips form in weak areas and are burnished (upper part of image)

 

GEN_16k_clean_denim_01

Cross-section view SEM image after stropping 30 laps on clean denim demonstrates a small but measurable micro-convexity is produced, increasing the near apex angle by 1.5 degrees.

 

In the subsequent images, stropping with progressively coarser poly-diamond spray is characterized.

 

GEN_16k_0p1PD_den_01

Shapton 16k followed by 30 laps on denim loaded with 100nm poly-diamond spray.

 

GEN_16k_0p1PD_den_02

Shapton 16k followed by 30 laps on denim loaded with 100nm poly-diamond spray.

 

Gen_SH16k_p25PD_den_01

Shapton 16k followed by 30 laps on denim loaded with 250nm poly-diamond spray.

 

Gen_SH16k_p25PD_den_02

Shapton 16k followed by 30 laps on denim loaded with 250nm poly-diamond spray.

 

GEN_16k_0p5um_den_10

Shapton 16k followed by 30 laps on denim loaded with 500nm poly-diamond spray.

 

GEN_16k_0p5um_den_13

Shapton 16k followed by 30 laps on denim loaded with 500nm poly-diamond spray.

 

Gen_SH16k_1p0PD_den_01

Shapton 16k followed by 30 laps on denim loaded with 1 micron poly-diamond spray.

 

Gen_SH16k_1p0PD_den_02

Shapton 16k followed by 30 laps on denim loaded with 1 micron poly-diamond spray.

 

Gen_SH16k_3p0PD_den_01

Shapton 16k followed by 30 laps on denim loaded with 3 micron poly-diamond spray.

 

Gen_SH16k_3p0PD_den_03

Shapton 16k followed by 30 laps on denim loaded with 3 micron poly-diamond spray.

 

GEN_16k_15umPD_den_01

Shapton 16k followed by 30 laps on denim loaded with 15 micron poly-diamond spray.

 

GEN_16k_15umPD_den_08

Shapton 16k followed by 30 laps on denim loaded with 15 micron poly-diamond spray.

 

The most striking observation that can be made of this series of images is that, with the exception of the coarsest (15 micron)  diamond abrasive, the amount of micro-convexity produced is insensitive to the abrasive size.  There is greater apex damage with the coarsest abrasives, but not an increase in micro-convexity.

Consistent with the earlier observation with the inexpensive diamond paste, the 15 micron diamond sprayed strop produced no micro-convexity.  Apex uniformity decreases with the coarsest abrasives, but at much smaller scale than the abrasive size. There is no unevenness or “micro-serrations” resulting from scratches of depth comparable to the grit size.

Observation with optical microscopy (not shown) indicates that the larger abrasives fall into the weave of the fabric and therefore do not make contact with the blade during stropping, other than glancing collisions that chip the apex at the submicron scale.  The same effect was observed with diamond-spray loaded paper (also not shown).  In this context, the result of the re-loaded strop described earlier can be understood.  The waxy carrier fills the spaces in the fabric, preventing the newly applied larger abrasive particles from entering the weave, leaving them exposed to the blade resulting in the substantial blade damage that was observed.

None of the diamond sprays produced an increase in near-apex angle as large as is typically observed with the various metal polishes.  This is most likely attributable to the oily and/or waxy carrier holding the abrasive in place and presenting it to the metal more efficiently than the water based diamond sprays.

 

Advertisements

50 responses to “The Pasted Strop – part 4

  1. More very interesting and thought-provoking stuff Todd. Keep’em coming!

    In terms of edge uniformity, the example photos look like .5 micron compound is sort of a “sweet spot” in terms of apex uniformity – is this just a coincidence in the photos you chose, or did .5 micron actually give more uniform edges on all your test razors?

    Like

    • Keep in mind that this is for denim strops, typical of woven materials.

      The results here are typical of what I observed with the other test razors. 0.5 micron seems to be the optimum for the denim strop. However, we can do much better by following it with 0.25 micron diamond on a leather strop.

      Like

  2. Would CrOx, if good quality and size distribution, fit into this “sweet spot” on denim, or would it behave differently from diamond? I ask because I’m sitting on a sizable amount that is collecting dust since I started with Mothers and Thiers. I guess I could test and see for myself how it feels.

    Like

    • Pure chromium oxide is generally a poor choice since it burnishes more than it cuts, but the “green bar” type that is a mix of aluminum oxide and chromium oxide should work well.

      In my experience pure chromium oxide is best used on a hard substrate like wood.

      Like

      • Do you mean hard like balsa or hard like oak ? I have best quality Cr2O3 rubbed dry onto balsa. In my imagination the particles sink into the balsa like you describe sinking into the denim weave- but imagination may be way off. Anyway, I can see the tiny bit of green on the steel and being dry it comes off real easy before moving to the plain leather.

        Like

      • I don’t think there would be much difference between balsa and oak in this application, the balsa is more porous, but still “harder” than a hanging strop in terms of transferring force through the abrasive particle. Loose particles have no effect, and can actually act as a lubricant preventing abrasion – this is partly why we don’t want too much compound on a balsa strop.

        Like

  3. I see you noted that a micro-convexity was created on the clean denim. What about normal stropping on linen then leather, does this create a convexity as well? I thought I saw some pics of this but may have confused it with the pasted strops.

    Like

    • Micro-convexity is created on clean denim, clean natural linen and clean newspaper, although the rate that it occurs varies between materials. The primary effect of adding abrasive is to speed up the process.

      Like

  4. I’ve devoured the info you posted here so far as it is ground breaking compared that there is this dogma that it HAS TO BE MULTISTEP.

    But another thing that would really interest me is the following:

    I know that you are more focused on straight razors but could you by any chance elaborate on high-wear resistant steels like S30V,S90V, S110V and the effects of trying to sharpen those on non CBN/DMT Abrasives and the effects on their edge keeness/sharpness.

    The common opinion is that the vanadium carbide making those kind of steels as wear resistant as they are would break off or not be fully polished if you for one would try to strop them with materials that are softer than itself leaving only CBN&DMT and that therefore a coarse edge would increase performance.

    The Question i ask myself now is, is it really the case when we take high grit DMT&CBN into consideration that could effectively polish Vanadium carbide Particles in the Steel?
    Or is it just the rule “Coarse Edge is Better for S**V Steels” because DMT/CBN Strops and what not isn’t too common around (non SR) knife sharpening?

    Thanks!

    Like

    • It should be clear from the evidence I have shown here that this is true. Additional stropping on clean leather is required, and if you prefer a very keen edge, 0.25 or 0.5 micron diamond on leather followed by clean leather works best. I would recommend you just try it yourself…

      Like

      • I’ve got autosol metal polish. Tonight I will load a piece of denim up and take a blade that was shaving well to the strop and test this method.

        Like

  5. Probably best to refresh the edge on 4-8k stone, ending in 20 or so edge trailing strokes, and THEN go with the polish, as the edge is probably already burnished or deformed from use, so the polish will have no effect. You want to abrade the foil edge off from the trailing strokes on the stone in order to remove just the last few microns of steel to form a new apex.

    Like

  6. Thank you for your hard work and for your generosity to share your knowledge. It finally reveals the phenomens that take place at the cutting edge. Is there a place for Chromium oxide in a routine of sharpening and maintaining the edge according to your findings? Part of the reason I entered the straight razor world was to avoid cartridges. Buying cartridges made me feel menopausal. Now the diamond is doing a great job but is expensive and the sprays seem rather small, while the amount of crox I have is going to last a life time provided is not very long. I am experimenting with crox on denim and hanging leather strop followed by clean leather. I was doing the crox on paddle strop and clean hanging leather before. I dont see much difference but I am just starting.

    Like

    • Chromium oxide is moderately effective on a hard surface, particularly wood. A balsa-wood strop is your best option if you only have chromium oxide. Because the crystals are smooth edged, they tend to cause more burnishing than abrasion on a fabric or leather strop.
      A small bottle of diamond spray will last a lifetime – you can do thousands of laps between refreshes on a leather strop.
      I would suggest you try the method with edge-trailing strokes on the hone followed by stropping with metal polish on hanging denim. The diamond spray on leather is not required, it just adds a bit more keenness.

      Like

  7. Thank you very much for sharing your time, expertise and findings with us … the sharp edge leaders … or are we the keen edge trailers? I am enjoying reading your blog.

    Your SEM images are very informative. Many hours with my 50x optical stereo microscope with a quartz halogen lamp has taught me a lot, but it doesn’t show what you have shared with us. Seeing is believing for the empirically minded … especially if followed by a “good” shave.

    I will soon sharpen my own skills by following your methods. I read somewhere that you can make an edge that is about twice as keen as a Feather blade (commonly thought to be the sharpest commercially available blade, because it is thin). A Feather or even a multi (five I think) Gillette Fusion blade scrape my beard off effortlessly and painlessly. My straight razor experiments have so far made an edge that is better than pulling out the hairs with tweezers, but not as good as shaving with a Feather. Now that I have a vision of what a keen edge should look like, I will aim to make my straight razor edge perform better than a Feather edge. If I succeed, I’ll be happy. You have shown us that we have abrasives that were not available to our grandfathers, so we should be able to make a better edge than was possible fifty years ago. The sharpening myths that have been passed down may work for some but we should be able to do better now — with your SEM photos to show what happens on the edge with different techniques.

    Your images show that stropping a honed blade on a Mother’s Mag and Aluminum metal polish pasted hanging denim strop give a very smooth looking edge, with an increased angle micro convex edge. The image of a 0.25µn diamond paste in a similar denim hanging strop show less angle increase of the micro bevel. Is the “diamond denim” edge more keen than the “Mother’s denim” edge? You have written about the sharpness being task related. Is beard hair generally too tough for a sharp and keen 0.25µn denim stropped edge? Is the greater angle of the “Mother’s” edge more durable and useful for shaving? Is a Mother’s stropped edge followed by a few laps on a flat leather strop with 0.25µn diamond even keener? You have suggested always stropping on a clean leather strop before shaving.

    I’ll compare the finishes myself … but I have to wait to find, buy and receive all the “stuff”. Patience, patience.

    In the meantime, I’ll read more of your blog. Thank you.

    Like

    • I would not be overly concerned with the keenness after the denim strops, both are improved by stropping on leather, even clean leather. In any case, the purpose of the charged denim is simply to pre-convex the apex to prevent a foil edge forming with the diamond charged leather strop – the metal polish loaded denim strop is more effective for this purpose. Smooth leather alone cannot remove a foil burr, so we want to avoid one altogether.

      The measured angles will depend on the force applied and the resiliency of the strop materials. The goal is to match the angles produced by the two strops – the absolute angle is not that critical, ideally in the low 20’s to balance durability with cutting efficiency. When you mention “flat leather strop” this suggests a paddle strop, which I do not recommend. What I do when stropping on the diamond charged leather is to test the blade on some very fine arm hair, when done correctly (to produce an edge keener than a Feather blade) I cannot feel the hair being cut (no “ping” whatsoever) but hairs are visible on the blade. To determine whether a foil is present you need to shave with the blade – if it is harsh or fades during the shave, there was almost certainly a foil present.

      Like

      • I have now read most of your blog… particularly Simple Straight Razor Honing which is not so simple (it’s all in the details)… but very informative and complete. Thank you. I made a summarized step by step (six steps!) set of instructions so that I would not make any assumptions and would really try to pay attention to every detail as you described the process. Having your SEM photos in mind and the knowledge of your many informative experiments gave me a vision of what I am trying to do. The rote honing prescriptions inherited from past shavers have never been encouraging for me.

        Now I have more “stuff”! I tried coercing the local teenager into giving me her designer jeans for the denim. She looked at me as if I were invisible. Okay, I’m too old. A trip to the fabric store yielded an eighth of a yard of cotton denim for $1.50. I also bought some 2″ leather strips off eBay ($20), found a scrap of ⅛ ” plexiglass at the hardware store and bought some CBN from Howard Schwartz ($50). I cut the plexi into 3×11 inch pieces to use as a flexible support for the denim and leather strops, as I have a waxed counter top that does not allow taping cloth to the surface. I now also understand the value of loom strops — and how about a Washboard sharpener! A neighbor gave me the remains of a jar of “Mother’s” and he also made me a razor with a piece of 440C steel (higher chrome, almost stainless), hardened and tempered. Why not? He recently bought some equipment for making knives. I realize that 440C may not be the easiest steel to sharpen… but that if I could make it sharp, other steels would be easier. He made the blade and edge more straight than I have seen from some custom makers. It is also hard (hardened and tempered to spec). It had about a 0.1 mm thick flat edge before I started sharpening with a 400 grit Suehiro Debado stone. I had to rub that rock for hours to get a burr on the edge! A DMT 1200 seemed to just glide along the surface. The tape on the spine was replaced a few times. I followed with a Naniwa 1k (green) stone and then a 2000 grit Debado and a 6000 grit Debado. The scratch pattern on the bevel was clearly evident with 50x magnification in a stereo microscope, with a slightly rough looking edge. The edge appeared to be rounded as it glinted in the light after the final edge trailing strokes. Perhaps that was a foil burr, but it looked like a rounded edge. I proceeded to the “Mother’s” loaded denim strop which I wrapped around a piece of leather, after drying it and rubbing the cloth to remove excess dried polish/powder, before rubbing the surface with the spine of the blade (tape on spine removed). I laid the leather/denim strop on a plexiglass strip which curved like a strop when in use… for about ten ~150g force laps. Under the microscope I could clearly see that the edge had “darkened” — no more shining striations near the edge — and straightened. There was no longer any glinting, and the edge looked very clean. It looked like a Feather blade edge, except the Feather has a triple bevel with the “dark” (no striations) polished edge, whereas mine has a single bevel with a polished edge. The Feather striations look like about 4000 grit. After washing the blade to remove any “Mother’s” grit particles, I stropped the blade on another piece of leather that is loaded with 0.025 µm CBN emulsion, laid on plexi. Then I lapped the blade on a clean leather hanging strop for about fifty light laps… then shaved.

        It was okay. I suppose the edge is about HHT-3… or maybe just 2. It pops head hair in an HHT test, but it does not slice it silently. The shave was close but not painless and not as good as I could have had from a new Feather blade. I need to try again. You emphasized that the most important step is setting the bevel. Perhaps I did not rub enough on the 6000 grit stone to make a foil burr. I noticed that a tiny chip in the edge did not go away… even after many laps. It seems like the 6000 grit just polishes the bevel which is about 0.75 mm wide. I will try going back to an 8000 grit Naniwa Fuji stone, which is a little softer, to try to make a micro burr before using the “Mother’s’ denim strop. Next time I will also try to use less force on the “Mother’s” strop which may be rounding the edge excessively. I will also experiment with the CBN strop, as you suggest that done correctly, the edge should “tree top” slice hairs off an arm. A friend’s beard has yielded a small tuft of hairs for my tests. Beard hair is hard to find in Summer around here.
        For a future experiment, I might try to apply the CBN to a piece of paper laid on a piece of the hard plexi… adding a little curve to the plexi. The idea would be to thin the shoulder of the convex apex, making it sharper. I also bought a piece of thin ultra suede cloth which I will try with CBN, laid on the hard surface of the plexi — flat.
        But first, I would like to just follow your directions again, until I get a better result. Force, pressure, number of strokes — leading and trailing — honing and stropping — and getting that pesky bevel right.

        I welcome any suggestions. I have not been able to find a definition of “honing”. Do you have one? Does honing start at a finer grit than “sharpening”? Sharpen a knife, hone a razor? What about a razor rubbed on 400 grit?

        Thanks again for sharing all your SEM photos and information. Most of us don’t have your specialized access to such equipment… or the knowledge
        . Fifty years ago, shavers had not even heard of such equipment.

        Like

      • I did struggle with the choice of the word “simple” when I wrote this. The key is that this approach is very repeatable even with small variations in the individual steps. There are some very critical points however – you must use edge trailing strokes near the end and you must use purely hanging strops. The edge trailing strokes eliminate the usual problems of setting the bevel. If you have formed a small foil burr, you have set the bevel correctly. By attaching your strops to sheets of plexiglass, you prevent them from doing what they need to do.
        The analogy I like to use is to imaging having a golf ball in your back pocket – would you prefer to lay on a thin carpet with the ball under you or in a hammock? The hanging strop is the hammock.

        Do you mean 0.25 micron or 0.025 micron (25 nm) CBN? I do not recommend any abrasive smaller than 0.25 micron (250nm).

        There is no universally accepted definition of “honing.” I use the term to refer to apex refinement as opposed to grinding to define blade geometry.

        Like

      • I’ve tried the technique and it worked well. I don’t recall there being anything in Todd’s method involving backing the denim and leather with plexi-glass or hard surface. I think this would limit the process from forming the necessary micro-convexity. The other thing is that you pulled the tape after the stones and before the backed stropping on denim and leather. This usually isn’t a problem and a free hanging strop but a backed one might not follow the altered bevel angle.

        Liked by 1 person

      • I should be more clear about the plexi support. It is very flexible. One end is placed near the edge of the bench and the other held in my fingers above the bench so that the denim/leather flexes like a hanging strop. I used a leather strip under the loaded denim so that the stropping angle would be the same as the leather with the CBN laid on the same plexi. I removed the tape so that the blade would slide easily on the denim and the leather. As you noted, with a hanging strop, the edge should easily meet the strop. The polished bevel — the last 0.1 mm, leads me to believe this is working.

        Since yesterday, I have made a few more edge trailing strokes on an 8000 Naniwa Fuji, followed by a little more pressure on the denim and CBN strops. The hone made a very small change… not enough to remove the tiny chip. I am now at an HHT-3, maybe 4. I think the edge would be 5 if I was honing a carbon steel blade — that’s next. Making this experiment more difficult is part of the learning.

        Anyone willing to define the difference between stone and hone?

        Like

    • I am referring to the simple straight razor honing method. I frequently use a rigid paddle strop with 0.25 micron diamond for knives; however, I can increase the angle and apply sufficient pressure to achieve the desired result.
      A rigid paddle strop with smooth leather does not make sufficient contact with the apex of a straight razor. The kangaroo paddle I use for knives has absolutely no effect on a straight razor. A flexible paddle strop (fixed only at the ends) or one made from rough leather will work, but it will be challenging to find the correct force. A hollow ground razor will flex and lift the apex off the surface if we use more than light force. By using a hanging strip of denim and a hanging strip of leather, you can use the same pressure on both (or slightly more on the leather) and the result is quite forgiving to the various conditions.

      Like

  8. Thank you for all your work. I have a sort of simpleton question. When you say strop with denim, does that need to be heavy duty denim tubing or canvas, or can it be something like old jeans? Thanks for any help.

    Like

    • I’ve tested a variety of 100 nm abrasives on a various substrates, and consistently observed a reduction in keenness. Prior to developing the denim with metal polish approach, I used 100nm CBN on leather as a burr-removal step. Forming a foil edge with 250nm diamond on leather, removing the burr with 100nm CBN on leather concurrent with a reduction in keenness, then restoring the keenness by stropping on the 250nm diamond on leather again.

      These sub-250nm abrasives can be very effective at producing a mirror finish, however.

      Like

      • I have still not mastered your system… but I am a believer, making progress and learning a lot from your experience. Thank you again for sharing all your observations and the SEM images. I think I now have a sharp edge but it is not yet keen enough to match or beat a Feather blade. I am missing the diamond step.

        In your tests, you observed that 100 nm abrasives polish the micro convex edge, much like finer than 8k grits are effective at producing a mirror finish on the bevel — without necessarily making it sharper.

        I had some 0.25 µm diamond spray called Dupont which I bought a few years ago. It makes nasty scratches on the bevel, so it is useless for razors — poor quality control. I did not know that before I bought some cBN 0.25 µm recently (sorry about calling it 0.025 µm in an earlier post) but that seems to be a “polisher” too.

        I see that Ted Pella sells 0.25 µm diamond grit in a spray and in a syringe, poly and mono crystalline. Choices, choices. Which do you recommend? I presume you have endured the expense of buying them all!

        While I wait for the products, I have been playing with what I have. I rubbed some silicon carbide 4000 grit paste into a sheet of printer “copy” paper, rubbed it in with paper towel, then placed the sheet of paper on a sanding screen (the type used for sanding drywall) laid on a hard flat surfaced wood block. The sanding screen makes very fine irregularities in the surface of the paper. My thought is that the grit cuts all the way to the edge because of the “corrugation” in the surface which raises the pressure on the edge. A few gentle edge trailing strokes over the paper with my razor makes a very nice looking, sharp scratch pattern in the bevel, finer and crisper than 8k aluminum oxide. The result pops hair. I imagine that any larger grit embeds into the paper, much like the larger Mother’s aluminum oxide grit particles sink into denim.

        Like

      • The 0.25 micron cubic boron nitride, in my experience, performs equivalently to both poly- and mono-crystalline diamond at the pressures we use for honing and stropping. I would expect that batch-to-batch variations in size distributions will have a larger effect than the type of particle.
        I use the 0.25 micron CBN and the Ted Pella diamond spray interchangeably – I would suggest you spend a bit more time with what you have rather than buying something else. It may be that your leather strop needs some break-in laps with a screw-driver shank.

        If you are not achieving “Feather Blade” levels, the problem is most likely with the diamond/leather step, or possibly too much pressure with the metal polish/denim strop. I would suggest testing the blade by attempting to tree-top arm hair after every 5 laps, starting with minimal pressure and slightly increasing each time. The ultimate keenness comes from just removing that last bit of metal burr from the apex.

        I have experimented with diamond spray on paper, and it behaves very much like denim – larger particles are embedded and play no role.

        Like

  9. SUCCESS! Thank you for your support. My CPM 154 stainless steel edge is now as good as a new Feather edge and a vintage carbon steel blade is much easier to sharpen.

    I have been refining my technique (within your parameters) by using less pressure and more strokes — and a lot of looking under a stereo microscope to make sure the entire magic marker blackened bevel is sharpened all the way to the edge, from heel to toe. The rounded edge likes to hide! I used an 8k Naniwa Fuji and 10k Suehiro Gokumyo (because I have them) to refine the bevel by making a thin slurry by rubbing the 8k with the 10k stone, then using the 10k stone with a thin 8k slurry which I thinned out to just water on the 10k after wiping the surface to remove any bits of burr from the stone surface, to avoid making a new chip in the edge. I finished with about twenty laps of edge trailing strokes, then polished the edge very lightly with the Mother’s pasted denim strop (about ten laps), followed by about twenty slow and careful laps on a 0.25 µm cBN pasted leather strop and finally about ten laps on a clean leather strop. A vintage carbon steel blade takes fewer laps at every stage and shaves painlessly. I don’t yet know if the CPM 154 holds its edge longer than a carbon steel edge.

    Under a stereo microscope at 12x and 25x, I noticed the familiar look of the perfect Feather blade edge which appears dark a few microns from the edge, with no glinting burr beyond the edge. Now that I have your high magnification SEM images in mind, the 12x gives a good indication of what is there. The polished dark edge, from using the denim and leather strops, looks different from the scratched bevel. With the light source angled appropriately, the dark polished edge is easily noticeable. Any burr, chips or deep scratches show immediately — very annoying.

    My struggling with sharpening a razor edge has given me a much better understanding of edges for knives. My kitchen knives respond well to the Mother’s denim strop after finishing on an 800 – 1000 mesh grit (Corundum sandpaper or stone).

    A bearded friend has donated some whiskers for HHT tests. Big thick red Viking hairs pop off easily, half an inch from the suspension point.

    The final result is my smooth face, and happy, admiring lady.

    Thank you for your guidance. Your SEM images and experiments have taught me more than any of the magical mystery tours that I have tried to follow in the past.

    Like

  10. Clive, interesting post. As far as your kitchen knife is concerned, did you do edge trailing at the end? I find it a bit difficult to strop on hanging denim (less so on hanging leather) near the tip since it “digs” into the denim. Did you go all the way to the diamond on leather for the kitchen knife? Thanks!

    Like

    • For the kitchen knife, I used edge trailing strokes for the final ten or so strokes, just as Todd recommends for a razor. Stropping the blade with a few light strokes on the pasted denim strop is probably more than is needed for a kitchen/utility knife, but I did it to feel the result. If the stroke is very light (that is all that is needed), the tip toe should not dig in. If the blade is long, you can pull the pasted “rag” (strop) over the edge under its own weight to remove any burr. A kitchen knife with a 1 µn edge is sharp by any standard, but that is ten times more blunt (less keen) than the minimum required for a razor edge if the razor use is to be less painful than pulling out the whiskers with tweezers. I stropped the knife on leather too, but it was probably not necessary and I don’t know if it made any difference. Making a razor sharp is a special skill and it was difficult for me until recently, thanks to Todd’s revelelations.

      Like

  11. Todd,

    Now that I have a useful shaving edge, I am curious to push a little further and widen my experience.

    Will a Gokumyo 20k or 30k stone improve the sharpness? I don’t have either.

    I finished my razor on a Gokumyo 10k stone (which I have) before using the polish pasted denim strop and cBN leather strop. Success.

    I notice that you finish with a Shapton 16k, and sometimes a Gokumyo 20k, but that you have also finished on 325 and 8k stones before the denim strop with good results. I think you have indicated that polishing the whole bevel is not important for shaving, as long as the last few microns of the bevel have the correct geometry and a burr free edge.

    Is there a benefit to finishing on a finer than 10k stone before using the denim strop?
    Your micrograph of a triangular bevel from a 20k stone looks very sharp. It occurs to me that following the 20k with very light strokes on the denim strop might make an even better edge — sharper and keener than from a 10k. Is that so?

    You have also written that a Coticule edge is just about perfect. Do you follow the coticule finish with a clean leather strop — or does the pasted denim and cBN stropping still apply? Does an Escher give a different result from a Coticule if followed by the pasted strops?

    Like

    • If you want to create a triangular apex (not micro-convexed by stropping) with sufficient keenness for shaving, then a Gokumyo 20k is the best (easiest) option.

      Personally, my beard is too coarse to shave with a blade prepared this way (the apex angle is too low and they do not survive a single shave).

      I have a Gokumyo 20k (somewhere under my sharpening bench) and it’s been a very long time since I used it for anything other than experiments. I have typically used this hone as a “control” to show the effect of other stones/hones/strops. There is very very little difference (less than 1/10 of a micron) between the apex formed by edge-leading strokes on the Shapton 8k and the Gokumyo 30k.

      Since stropping on abrasive denim will form a new apex a few microns below, these differences are of no consequence. I have gone from the Shapton Pro 320 (edge trailing) directly to the denim strop with several razors and the results were indistinguishable from that produced by higher grit hones, both by SEM measurements and shave-testing.

      If done correctly, a Coticule honed razor only needs a clean leather strop to finish.

      Like

  12. Todd,
    Your research is mind blowing. I’ve read all of your articles, and I feel enlightened! It totally changed the way I understand honing. Thank you.

    I still couldn’t try your simple razor honing method, because my diamond spray is still in mail. However I’ve been experimenting with the honing and AlOx denim stropping parts, i.e. first two steps.
    After finishing with edge trailing strokes on a Shapton GS 8k as you described, I continue with a denim strop loaded with TI pate a rasoir. I haven’t achieved a shaving level comfort yet, even though I observe that tree topping of arm hairs and HHT is greatly enhanced this way, more than I’ve ever got. This is curious. Am I achieving high level of keenness, with a very low level of sharpness? I hypothesized that I’m micro convexing the apex too much.

    Also, I’m curious, why is a foil burr needed before forming the micro convex apex. Why can’t the abrasive denim strop do the same thing to a triangualar apex?

    Like

    • Within my definitions of keen and sharp, yes we give up a bit of sharpness to improve keenness. When you strop on the strip of denim loaded with TI pate a rasoir (or any metal polish, there is very little difference between the common varieties) you create some micro-convexity while making the apex narrower and more uniform. The amount of micro-convexity is mostly determined by how much pressure you use, so you can reduce this by simply applying less pressure. This is something you can experiment with and test by attempting to tree-top your arm hair.

      The diamond spray is not absolutely necessary – you can achieve almost the same result with a clean leather strop. In any case you do need to strop on clean leather before testing.

      You are correct that a triangular apex is sufficient for this procedure; however, it is not always easy to produce a triangular apex. For example, the 6k side of the King combination hone doesn’t produce a suitable apex by edge-leading strokes alone. There are a number of pitfalls in honing and stropping that I haven’t discussed that are avoided by following the procedure as described.

      Like

      • I finally received my Mother’s polish and gave your “simple honing method” another go. The result was the sharpest (or should I say keenest) edge yet one of the most comfortables, if not the most. I’ve been honing for a year, and I hadn’t come close to this level with my synthetic stones, JNATs and CrOx. The way I look at honing has completely changed. Now it’s not about grits, scratch patterns, sizes, but the geometry at the apex. Thanks again.

        After gaining some experience with the Mother’s polish, I’ll give TI pate a rasoir another go.

        Like

  13. As far as knives go, I find it fascinating that Rockstead Knives advises the use of a denim strop loaded with polishing compound as the best maintenance and uses them in their demonstration videos.
    Their knives are renowned for their edge–as well as their price!

    Like

  14. Your website is really a great place to get lots of information about everything concerning razor blade sharpening. Very informative!

    I personally use a pasted leather strop with iron(III) oxide to give my straight razors the final touch. I found a special artists oil colour from the German manufacturer Schmincke (Terra Rosso) which contains very fine iron(III) oxide particles that makes it very suitable as strop paste for this special job. Fe2O3 is quite less abrasive than chrome oxide and therefore achieves better stropping control and results in a really smooth and sharp edge. I also use this pasted strop to resharpen my straight razors of they get a little bit dull after longer time of use. The results are really satisfying.

    Best regards
    Norbert

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s