Stropping Query

A few months ago I made myself a bench strop from some kangaroo leather (tail if I remember) that I bought on the net. I have loaded this up with chromium oxide.
I have enough leather left over to make another strop, should I want to.

The question is would it be worth making a second strop and using it as a bare leather strop after using the chromium oxide strop ?
What would be the benefits ?
Would it be worth having a second strop with something finer than chromium oxide loaded onto it ?


I am a home cook with far too many Japanese knives, so I tend to rotate them a bit.
My sharpening routine consists of 1000, 4000 and 8000 stones, followed by a cork for deburring and the strop for a final polish.
I have been sharpening VG10, 19C27, HD2 Kono steel, blue 2, blue super and some generic carbon steel from a cheap yanagiba.
I seem to get them sharp enough to shave my arm with my current setup - certainly sharp enough for practical use by myself. I am fairly new to all this and am curious if there would be any benefits of a second strop - or am I just over thinking this in my newbie enthusiasm/ignorance ?

Any information, thoughts or critique would be appreciated.
Cheers
Kev

Are you intentionally excluding coarser compounds? My 2 micron strop gets a lot of use...

riba said:

Are you intentionally excluding coarser compounds? My 2 micron strop gets a lot of use...

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Nope, you can put that down to pure ignorance

I never used/tried a bare strop (perhaps I'll learn something from this thread) for kitchen knives, but have a variety of strops to play with (2, 0.75, 0.1 CBN, 0.25 diamond spray, ...) (I straight razored for a while ).

If f I'd have to start afresh, I'd get a bit of a coarser compound (say 1 or 2 micron) and one in the 0.25 ballpark. (Don't care whether it is CBN, or diamond spray)

riba said:

I never used/tried a bare strop (perhaps I'll learn something from this thread) for kitchen knives, but have a variety of strops to play with (2, 0.75, 0.1 CBN, 0.25 diamond spray, ...) (I straight razored for a while ).

If f I'd have to start afresh, I'd get a bit of a coarser compound (say 1 or 2 micron) and one in the 0.25 ballpark. (Don't care whether it is CBN, or diamond spray)

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Any idea where chromium oxide sits in the micron range ?

Green chromium oxide compound is typically 0.5 micron.

I use it to polish watch crystals and buff up dirty or tarnished gold and silver, with great care -- easy to "polish" right through rolled gold and electroplate will vanish quickly!

Use with care on a strop, it cuts rather quickly. I use a smooth leather strop on wood, plus chromium oxide on a piece of 2x4 that is smooth. Works great if you use very very light pressure on the wood.

Peter

@psfred, Chromium/aluminium oxide are both very hard stuff, use with extreme care on soft metals like brass, copper or gold! Product like BRASSO is more suitable for delicate metals.

Good quality chromium oxide is 50,000 grit equivalent. I use it as a final polish on gemstones.

I only use chromium oxide when actual metal removal is required, mostly on WWII era watches where the base metal is sterling silver rather than brass (equally true of gold fill fountain pen caps and trim in those years). Brass was rationed, so the case companies used silver instead, and silver will slowly migrate through the gold and then tarnish, turning the cases black and nasty looking.

needless to say, I'm rather careful. It's quite easy to remove far more metal than necessary with over-vigorous use.

Chromium oxide on a solid surface or very hard leather is a great hone for edges though, polishes very quickly with very light pressure and will leave the edge quite clean. Too much pressure and the edge will roll over though, as I've found by doing so. Turns black with metal particles as soon as you wipe a blade over it.

Peter

I don't find chromium oxide to be good for kitchen edges at all. Even with light pressure I think it polishes too much. The edges are too smooth and it can roll edges easily as well. The knife will then cut paper and shave great, but often fail the 3 finger test.

I like 1 micron diamond on hard felt, mostly just for deburring properties, not as much polishing/refining.

One other thing I've heard about chromium oxide is that it's genotoxic, meaning it can cause mutation. It's also carcinogenic.

In the amounts you'd probably have on a knife blade, I've no idea if it would make any difference, but something to keep in mind. Do some research and decide.

Diamond pastes are generally what I use, and for sharpening/touching up blades is much easier than stones for a novice IMO. A 4-sided strop is a great investment IMO.

Chromium oxide is pretty harmless unless you ingest large quantities. Hexavalent chromium ions, rather than the trivalent ions in chromium oxide, which are only soluble in strong acids, ARE carcinogenic and acutely toxic. Hexavalent chromium is usually found in industry as chrome plating bath in strong sulfuric acid, very unlikely to get into food in the kitchen. Besides, you DO clean your knife after sharpening, right?

Wash the blade after stropping and you will be fine -- probably more chrome in the black swarf from stainless steel than in the stropping compound for that matter.

Peter

I kind of agree, I generally only use chrome oxide on my straight razors, and try to wash well afterwards. But just something I read and passing on, likely nothing to worry about.

psfred said:

Chromium oxide is pretty harmless unless you ingest large quantities. Hexavalent chromium ions, rather than the trivalent ions in chromium oxide, which are only soluble in strong acids, ARE carcinogenic and acutely toxic. Hexavalent chromium is usually found in industry as chrome plating bath in strong sulfuric acid, very unlikely to get into food in the kitchen. Besides, you DO clean your knife after sharpening, right?

Wash the blade after stropping and you will be fine -- probably more chrome in the black swarf from stainless steel than in the stropping compound for that matter.

Peter

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droshi said:

Diamond pastes are generally what I use, and for sharpening/touching up blades is much easier than stones for a novice IMO. A 4-sided strop is a great investment IMO.

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How would you use a 4 sided strop ?, as in what combination of pastes, I guess !?

Could you use a combination of strops in lieu of stones for sharpening ?
Haven't heard of this before.

I've done a fair bit of googleing but have not really found a coherent discussion of strops and their uses in relation to different pastes. There tends to only be fairly specific fragments as part of a different discussion, or fairly specific query.

I did come across one statement a while ago that loaded strops were for sharpening and bare strops for honing. There was no further statement/explanation on that case.

kevpenbanc said:

How would you use a 4 sided strop ?, as in what combination of pastes, I guess !?

Could you use a combination of strops in lieu of stones for sharpening ?
Haven't heard of this before.

I've done a fair bit of googleing but have not really found a coherent discussion of strops and their uses in relation to different pastes. There tends to only be fairly specific fragments as part of a different discussion, or fairly specific query.

I did come across one statement a while ago that loaded strops were for sharpening and bare strops for honing. There was no further statement/explanation on that case.

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Basically you load a 4-sided strop with 4 different pastes. Usually in a progression that makes sense for your setup. If you don't have much for stones, I'd probably start somewhere around 15-10 micron.

Although many people just load them for use after their main line of stones, you can easily set a bevel on a straight razor with an 8 micron diamond paste. Diamond pastes cut pretty fast.

For knives I would still get coarse stones for setting bevels and fixing major nicks, but for maintaining an edge, assuming no major damage, diamond pastes will do really well in my experience. A 4-sided strop has a stiff backing, which is generally what you want for the coarser pastes. You can also get some bench strops (similar looking to a stone, but made of leather or felt glued or velcro'd to a flat piece of wood) and load them up with pastes.

A hanging strop works a bit faster with finer pastes.

One last thing to mention, a bare leather strop won't hone a blade, it simply aligns the edge of the steel (similar to using a bare steel rod on a knife). When cutting hair the edge of a razor gets tore up microscopically, so the leather just pulls those small pieces back into alignment. There's also the idea that over a bit of time the steel will "grow" and tend to stick back to the main body of the razor, and if you let it do that process for about a week after use you can extend the life of the razor and it will need less honing on a stone. This is why they make 7-day razor sets, though I don't know if it actually matters much in practice.

I am curious about this as well. I have a two sided strop that came with red, white and green compounds. Are there standards for the red and white as it sounds like there is for green? I've definitely found the strop with green compound to put a hair-splitting edge on most knives after a 6k stone. I do think this is more polish than is useful for most kitchen tasks...

Also do you have a recommended source for diamond paste?

i got a piece of red compound from a local jeweler, apparently the red compound is in most cases iron oxide (a.k.a rust), and is to soft for hard stainless steel.

when it comes to jewelers compounds (rouge), some makes make 2 kinds of green compounds, one for final polish and one for medium polish.

psfred said:

Chromium oxide is pretty harmless unless you ingest large quantities. Hexavalent chromium ions, rather than the trivalent ions in chromium oxide, which are only soluble in strong acids, ARE carcinogenic and acutely toxic. Hexavalent chromium is usually found in industry as chrome plating bath in strong sulfuric acid, very unlikely to get into food in the kitchen. Besides, you DO clean your knife after sharpening, right?

Wash the blade after stropping and you will be fine -- probably more chrome in the black swarf from stainless steel than in the stropping compound for that matter.

Peter

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Think it is a good idea to wash the blade after stropping no matter what compound. Don't think want to ingest Chromium Oxide or diamond slurry. I tried C. oxide went back to my favorite Adams #2 polish, I do wash my blades after stropping. Use blue goop to clean & condition the leather.

I tried C. oxide went back to my favorite Adams #2 polish

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How toothy of an edge does the Adams polish leave?

i have recently started to use "peek metal polish", it is roughly 20% of ~2 micron alumina, and the first thing i found out about stropping, is that it is very easy to over do it.

this stuff removes metal so quickly i found myself with a toothless edge after only 5~6 gentle passes on each side, after coming from 2K(P) paper.
after re-toothing of the edge, i just gave it ~3 gentle passes on each side (on flattened serial box cardboard), this was enough to give the edge a very delicate toothy feeling (that goes through tomato peel like it was thin air), and give the edge an almost perfect mirror polish (with a bit of a haze).

i don't know how other compounds behave, but this stuff is very aggressive and will turn the compound loaded surface black with metal particles after the first pass, i guess compound that are intended for stropping could be more concentrated and cut even faster.

Aluminium oxide cuts real aggresively. Only 3 passes is all you need to refine the final edge after the finishing stone. After that, it will push-cut paper like butter. If you over-strop with alumina, the edge will fail the fingertip test. If done just right, like within 3 passes, it will feel wicked sharp that will bite through skin with very gentle touch on the fingertips. Be very mindful when stropping with alumina, test with finger tips from time to time.

If I do over-polished an edge, I will very carefully strop again to regain the toothy edge. I think it's the angle that matters. My cheap stainless knives all get hair-popping sharp with this stuff, my arm hairs just jump away when they meet this new razor edge.

I only do one pass each side. Adams #2 is finest in their line. Light pressure. Cleans up edge & puts a nice polish. Sails thru tomato's. Angle is important as always, same as last on the stone or just a hair higher. You can lay knife on the leather very lighty push forward while raising spine, when it grabs that's your angle. When I say light mean it you do not want to slice your leather with this method.

Lateral sweep burr removal on stone is one stroke, extremely light touch. Even newspaper & strop correct angle & light pressure more important than repetition.

I simply lay down a bamboo chopstick on the spine as a gauge, it's exactly the same angle on the finishing stone, and strop at that angle. Always use an angle guide for consistency. Coins, dowels, folded paper, whatever available.

chromium oxide is a very good compound, I think compared to my 0.25um diamond spray, the chromium oxide leaves a toothier edge and the feeling is better than the 0.25um diamond spray.

You guys need some straight razors! Johnny Chance was right--kitchen knives don't need that refined an edge and it's only fun for the first few slices and then your right back to your original edge. You also have to be very careful not to ruin your edge.
Cheers

Don't know if you guys have seen this paper, machalik linked to it on a thread over at cheftalk:

https://www.wickededgeusa.com/files/knifeshexps.pdf

In relation to part of my original query it seems to indicate that a bare strop had no visible effect on a knife of 60 hrc.

chinacats said:

You guys need some straight razors! Johnny Chance was right--kitchen knives don't need that refined an edge and it's only fun for the first few slices and then your right back to your original edge. You also have to be very careful not to ruin your edge.
Cheers

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was thinking the same thing. i dont get all this stropping talk with compounds. i strop a bit just to make sure burr is gone but thats it. 6k stone is already as fine as i need to go and in many cases less.

kevpenbanc said:

Don't know if you guys have seen this paper, machalik linked to it on a thread over at cheftalk:

https://www.wickededgeusa.com/files/knifeshexps.pdf

In relation to part of my original query it seems to indicate that a bare strop had no visible effect on a knife of 60 hrc.

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Interesting read. Not exactly kitchen knife test, but very informative.
I was surprised to read that edge leading stroke was deemed to be better on the stones compared to edge trailing. Especially since most experience people recommend more pressure on edge trailing.

Ruso said:

Interesting read. Not exactly kitchen knife test, but very informative.
I was surprised to read that edge leading stroke was deemed to be better on the stones compared to edge trailing. Especially since most experience people recommend more pressure on edge trailing.

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thats my experience with razor sharpening, edge leading is best. think its getting a bit too technical for kitchen knives

I would never shave with a razor finished on a 6k stone but that feels way more than enough (and overkill sometimes) for kitchen knifes. i think the pursuit for the sharpest knife is a bit silly...yes sharp (very sharp) is good, but it needs to last. if you guys like pushing metal to its absolute limits you should get into sharpening straight razors...which you can really push the edge to be ridiculously sharp.