Stropping: what micron size paste?

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evert67

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Oct 22, 2011
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I am going to try to strop my knives after sharpening, since I have read good stories about the effects of stropping. I wondered, however, how fine a micron size (or equivalent grit size) the stropping paste should be. I can get stropping paste/spray in the range of 15 - 0.25 microns.

For example, if I have sharpened a knife on a 1000 grit stone (which, according to the unified grit chart of this forum and elsewhere, is equivalent to 8 microns), I would imagine that I should start stropping with a paste that has particles that are slightly smaller than 8 microns, e.g., 5. And after that I could go down in micron size, for example strop with a 2 micron paste.

Similarly, if I have sharpened a knife on a 1600 grit stone, which is equivalent to 2.85 microns, I would imagine that I should start stropping with a paste with particles of, e.g., 1 micron.

However, I read stories where people start stropping with pastes at much higher micron sizes, e.g., 15 microns after sharpening on a 1000 grit stone or 5 microns after sharpening on a 1600 grit stone. I would think this actually dulls your knife rather than sharpens it. :confused:

Can anyone tell me which micron size paste/spray I should start stropping with for the best effect?
 
What type of abrasive are your stones? Are they diamond, silicon carbide, aluminum oxide (ceramic), etc?

Depends as much on the hardness and shape of individual abrasive types, aside from simple particle size. If your 1000 and 1600 grit stones are of the same abrasive type as the stropping pastes (all diamond, all silicon carbide, all aluminum oxide, etc.), then a correlation between sizes is (sometimes, not always) more meaningful. Otherwise, not much correlation at all. Diamond cuts much more aggressively than either silicon carbide or aluminum oxide, even at smaller particle sizes. Silicon carbide's shape is more jagged than aluminum oxide, which will greatly influence how aggressively it cuts, independent of size. Also take into account, the binders used in the stones (aside from their abrasives), and how the stone was manufactured & finished, can/will make a big difference in the finish they leave, as compared to the raw abrasives in the pastes/sprays. And for the stropping compounds, there will be big performance differences in the backing used, like leather, hard or soft wood, paper, cardboard, etc. A firmer & harder backing, like hard wood, will make a compound work more aggressively than it will on leather (faster, and will cut deeper into the steel).
 
Thanks Obsessed, my stones are all diamond stones, only the 1600 grit stone is a ceramic one. All of the stropping compounds I will used are diamond based. And I'll probably strop using some leather on a hard wood back.
 
evert67 said:
Thanks Obsessed, my stones are all diamond stones, only the 1600 grit stone is a ceramic one. All of the stropping compounds I will used are diamond based. And I'll probably strop using some leather on a hard wood back.
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That simplifies it a bit. For the moment, setting aside the ceramic hone, I think you'd be fine using something like 6 micron paste (I'm referencing DMT's example) after your ~8 micron diamond hone, especially if you use the compound on hard wood. Beyond that, take the grit progression as far as you want. I think most seem to be happy with edges down to 1 micron (myself included). After that, a lot of other factors start influencing the quality of finished results. Poor technique, the backing used for the compound, and simple dirt/dust on the strop can undo much of what the really small compounds might achieve. Take it as far as you think your skills will allow.

As for the ceramic hone, I'd think the 1600 grit probably leaves a fairly high finish. I use medium and fine Spyderco ceramics, and the white (fine, ANSI ~1200 grit) leaves a near polish (hazy) on my edges. Personally, I'd avoid trying to 'mix' the ceramic hone into your diamond sequence, although there's no harm in experimenting with it to see where it might fit. I use my ceramic hones a lot for de-burring edges. I have another Spyderco ceramic that I'd lapped with a diamond hone a while back, and it produces a finish something 'beyond' the Fine (white) Spyderco hone. Since it's one I did myself, I have no idea what the equivalent grit would be for it; maybe similar to Spyderco's UF, but I don't have one of those to compare to. I often use that re-finished hone to do some light polishing, and I often follow it with 1 micron diamond paste on red oak, then on leather with 1 micron paste. Produces a pretty nice finish, and great edges, this way.
 
Thanks again, David. That clarifies a lot. However, why would you avoid 'mixing' in the ceramic hone? (Is that the difference between the high finish and the nearly polished hazy finish? I am not sure what that means - English is not my first language.)

Are ceramics more abrasive than diamond? I thought it was the other way around. That said, I only know my diamond stones work faster than equivalent ceramics ones
 
evert67 said:
Thanks again, David. That clarifies a lot. However, why would you avoid 'mixing' in the ceramic hone? (Is that the difference between the high finish and the nearly polished hazy finish? I am not sure what that means - English is not my first language.)

Are ceramics more abrasive than diamond? I thought it was the other way around. That said, I only know my diamond stones work faster than equivalent ceramics ones
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I only recommended not mixing it in the sequence now, because it's difficult to predict what finished result you'd get from using it in combination with the diamonds (switching between abrasive types). That's also why I mentioned experimenting with it for a while. That's how I came to use my 'refined' Spyderco hone prior to using the 1 micron paste. I just kept fiddling around with it, until I discovered it fit well in that capacity. If you do find a spot for it in the sequence that works for your goals, go for it. My description of 'high finish' refers to a shinier, more polished one (mirror-like, or very close). And 'hazy' would mean a bit less polished than that (like a 'fogged mirror', for example). Sorry for the ambiguity in my descriptions. :)

Diamonds are indeed more abrasive than ceramics, for a given particle size.
 
Well, sounds like I'm prepared for actually doing it (once I've got the stropping compounds).

The diamond stropping compound, by the way, is quite expensive. Instead I can also get "generic" green, white and red stropping compounds. I think they are some sorts of oxides, but I am not sure what they are. Does anyone know what they are and (maybe more importantly) what their micron sizes are?
 
evert67 said:
Well, sounds like I'm prepared for actually doing it (once I've got the stropping compounds).

The diamond stropping compound, by the way, is quite expensive. Instead I can also get "generic" green, white and red stropping compounds. I think they are some sorts of oxides, but I am not sure what they are. Does anyone know what they are and (maybe more importantly) what their micron sizes are?
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I'd first ask the manufacturer/dealer about the specifics of their green/white/red compounds. The 'generic' stuff is a gamble, somewhat, for both abrasive type and size. If the dealer can't/won't specify what it's made of, I'd avoid buying it. Green is usually chromium oxide, but might be mixed with other abrasives (aluminum oxide seems to be a common additive). White compound might be aluminum oxide, but there are other 'white' compounds using other less-effective abrasives (as used for steel, anyway). Red is usually iron oxide, and will likely be too soft for modern alloy steels. It's usually intended for jewelry and other softer metals (like brass/nickel).

The diamond compounds might seem expensive initially. But a little of it goes a LONG way. It'll last a long time. For the money, I think it's a good deal. You can also get better quality green compounds from more reputable dealers (HandAmerican has a good reputation for all the compounds they sell, including their diamond pastes/sprays and green compounds).
 
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When I used my EdgePro I'd strop with the Bark River green and black compounds, then I'd go to the Mother's Aluminum Maq Polish. Excellent results every time. Like most of these compounds, a little can last you a good while.
 
What does the Aluminium Mag polish add to this? It hardly seems to have an effect on steel, or am I wrong? And am I correct in assuming you first strop with the black compound and then the green?
 
David, you are very helpful. Just to get a little idea of the costs and way of working. How much of the 5 micron liquid diamond paste would you spread on a leather strop backed by hard wood that is about 10" by slightly over 1"? And of much of 1 micron spray? I've heard stories ranging from the knob of the needle (how do you get that spread over 10" square?) via a tea spoon to "apply it liberally".
 
evert67 said:
David, you are very helpful. Just to get a little idea of the costs and way of working. How much of the 5 micron liquid diamond paste would you spread on a leather strop backed by hard wood that is about 10" by slightly over 1"? And of much of 1 micron spray? I've heard stories ranging from the knob of the needle (how do you get that spread over 10" square?) via a tea spoon to "apply it liberally".
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You'd be surprised (I was, and still am) at how little compound it takes to cover the strop. One way that makes it easier to spread diamond paste, is to use a flexible 'spreader' of some sort to more evenly spread out the compound. I used a plastic, flexible 6" ruler like a putty knife. Put perhaps a half-pea-sized drop in the center of your strop, and use the plastic spreader to distribute it evenly over the leather. If you 'squish' the compound under the spreader, it'll spread out to a very thin, and very even coating that can be spread easily. The edge of the ruler can be used to scrape up & collect any excess that accumulates near the edges of the leather, and then re-distribute it wherever it's needed. The layer of compound should NOT be thick, at all; a very thin coat works best anyway. Think of a layer that's ONE particle deep; that's all you need. I wouldn't think you'd need more than 3 drops of compound, maybe only 2 drops, to cover your 10" x 1" strop. The first drop's application should give you a pretty clear idea, based upon how much you can cover with it. For what it's worth, every time I've re-applied diamond paste to my strops, I always have ended up with excess left over (which then gets applied to a new stropping surface; I don't like to waste any of this stuff).

I haven't used the spray. But same principle applies. Very, very light. With any compound, "apply it liberally" is a waste, and won't work any better anyway. Sort of like stropping on mud, when it's that thick. The compound in direct contact with the leather has something to embed into, and anything on top of that just gets pushed around by the blade (and a lot of it will have to be wiped off the blade, when you're done).
 
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