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November 25, 2018 Comments (0) Knife Sharpening, stropping

Loaded Strops: Leathers and Other Materials Under 200x Microscope

The previous installment explored stropping mediums in their natural states without any abrasives to influence their action. We now enter the world of Treated Strops and Loaded Strops.  Depending on who you talk to, there is a either a slight or no difference between treated and loaded strops. For the purposes of jumping up and down on you in the rabbit hole (and to be thorough), treated strops are a kind of middle ground between unloaded/clean strops and loaded strops since they are treated or impregnated with varying mixtures of oils, fats and waxes that may or may not have some mild abrasiveness to them – think toothpaste levels of abrasion. Loaded strops encompass treated strops but differ in their intent, which is usually for more aggressive action to bring out a polish or a higher grit finish with the use of harder abrasive such as Chromium Oxide or Diamonds. As for treated strops this will be quick section with only Cow and Horse leathers since the rest of the mediums in our discussion are more commonly used as loaded strops.

Check out Jende’s stropping abrasives here.

Cow Leather Strop Treated with Neatsfoot Oil

First up is Cow leather treated with neatsfoot oil. Neatsfoot oil is a classic treatment for strops that keeps the medium hydrated and supple, and the oil acts to create a stronger surface contact with the blade called “draw”, and arguably helps prevent rust and corrosion of the blade. The overall structure of the cow leather is the same as the untreated in this case but the scales in the hide are more clearly defined. The raised oily scales are what creates the draw as it suctions onto the blade as it is stropped.

Horse Leather Treated With Wax & Oil

Next up is treated Horse leather, the most desirable being shell cordovan, a very specific, prized cut of the butt region of the horse hide. We saw the suede side of the horse strop earlier, and now we will see the reveal, and just how smooth horse leather can be.

The plateaus of the suede picture were made flat and treated with waxes and oils in this particular case, making the surface more or less homogeneous and flat. This flatness and consistency is ideal for straight razors in particular for adjusting the edge with practically no interference or abrasive action at all.

That brings us to loaded strops.

What’s A Loaded Strop?

Loaded strops are just that – strops that have been loaded up with something to enhance its function. Unlike treated strops, which try to minimize abrasion, loaded strops aim to bring more abrasion to the game. But before that, we’ll need a quick intro to abrasives and loaded strops.

I’ll try to keep this short, since it is really another entire series *wink wink*. There are several methods of delivery for abrasives used for loading strops:

  1. Rouges
  2. Pastes
  3. Sprays and Emulsions

You can also generalize these all by simply calling them stropping compounds.  Rouges are usually in a solid bar form, and are waxy and crayon-like. There are literally a rainbow of colors available with the different colors having different aggression levels based on their respective abrasives. Green Chromium oxide and Red Jeweler’s rouge are very common, but you also have black, white, blue and even pink compounds.

Pastes are not quite solid and not quite liquid forms, and can be almost anything from talc like abrasives all the way to diamonds. They are often housed in tubes or syringes, and traditionally used for loading the fabric based strops because of their thick consistency.

Sprays and Emulsions (including suspensions and slurries) are liquid with sprays being watery and emulsions having more of a hand cream consistency. Diamond and CBN abrasives dominate this type of delivery method currently. They work by leaving a coating of abrasive over or on a surface after the liquid portions evaporate.

That takes care of the very quick abrasive intro. For the loaded strop section, We will use the same mediums in the same order and magnifications as the unloaded strops, only this time they are all loaded with Jende 0.25 micron poly diamond emulsion. I wanted a thinner coating so the stropping medium itself was still visible so we could better see how it might react once a blade was run across it.

Loaded Cow Leather Strop

Cow leather is up first. It looks like it snowed in cowville. Now we can imagine blade coming into contact with the scale-like diamond impregnated ridges on the surface of the strop.

Loaded Kangaroo Leather Strop

Kangaroo leather tells a slightly different story – a winter landscape with much less overall surface variation that scratches on a very even plane, despite the small divots.

Loaded Pressed Felt

There is no horse leather picture, so we will move on to pressed felt. It looks more like morning frost on spaghetti, but the individual strands of the felt have been coated, giving each thin strand the ability to scratch. Given the random arrangement of the felt, you could get a short dot or a long dash of a scratch, and in any direction.

Canvas and the rest of fabrics

Canvas and the rest of the fabrics have a more consistent form. The weaves and threads are arranged so you basically get some sort of wide or long scratch that is the dimension of the weave itself, with stray scratches from the random loose threads.

Cotton, Linen and denim are in the same general boat as canvas, with their threads and weaves influencing the overall scratch depth and consistency.

Nanocloth Loaded Strop

Next up is Nanocloth. We can see how the honeycomb structures fill up with the abrasive, and have quite a dynamic capability because of the abrasives themselves and how they are grouped into a shape by the nanocloth (more for later discussion!)

Newspaper Loaded Strop

Newspaper actually has a smooth flat surface, and when loaded maintains that smooth flatness which is beneficial.

Cardboard Loaded Strop

Cardboard, as discussed with the clean mediums, is another flat surface. The lower quality corrugated cardboard has some gaps in material while the higher quality smooth cardboard is more consistent.

Low quality corrugated cardboard:

High quality smooth cardboard:

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