Strop Compound Colors

Pima Pants

Pima Pants

Gold Member
Joined
Jan 19, 2000
Messages
768
I recently received a strop that I ordered and it came with directions about how to use it. It has two sides, a rough suede and the other side is very smooth. What wasn't included were instructions on how to use the green compound or the white compound that came with it. I have used strops before but not with compounds. Any advice is appreciated.
 
The color of the compound tells you what level of grit it is, but it doesn't seem like there is a whole lot of agreement between manufacturers on what color means what. I have a green that's relatively coarse and a much finer white, and another white from a different brand that's somewhere between the 2. If there's a brand on the container, that will help greatly in looking it up. Otherwise, there are some good tutorials in old threads on loading strops with compound, and everyone has their favorite method. I like to heat up the coarse green until it's a bit softer, then scribble it on. I use a rougher leather for the coarse, and fine compound on the smooth side of the leather for polishing. I could be doing it completely wrong, but it works well enough for me.
 
Compounds would be better described in terms of their aggressiveness at polishing, rather than actual grit size or fineness. The actual size of the grit won't necessarily determine how it finishes a particular steel. 'Green' compound, if it's pure, will usually be a very fine chromium oxide at around 0.5 - 1 micron in size. It's not very hard either, as compared to a 'white' compound (usually aluminum oxide). So, between green's small size and lesser hardness, it won't be as aggressive a polisher as will be the aluminum oxide.

Because aluminum oxide is harder than chromium oxide, its 'white' versions can be very aggressive polishers on steels with a little more wear resistance - these would be stainless steels like 420HC, 440A/C, 154CM, VG-10, etc. Even though a 'green' chromium oxide might be smaller ('finer') and less hard, it'll struggle to fully polish some of these steels - so it won't leave as fine a finish, if there are many coarse scratches in the steel.

'White' aluminum oxide compounds can vary more in size (I use one that's rated at 2-5 microns). But with moderately wear-resistant steels as mentioned above, it'll be a better polisher than will the green.

Green compounds will polish well with simple carbon steels (1095, CV, etc.), because those steels have much less wear resistance in the form of hard carbides that would otherwise be found in the stainless steels mentioned earlier.

Best way to evaluate how they work is just to use them. You might test them first on plain paper laid over your bare strop, so you can get a feel for how they fit in a polishing sequence. When you have a better feel for that, then you can go ahead and load your strop with your preferred compound.

For me, if I have a 'green' and a 'white' compound - I'd make my choices based on what steels I'm working with, as explained above. I wouldn't generally use both in a sequence however, as they both can produce similar results on their own when chosen for a specific steel based on its wear-resistance alone.
 
Last edited:
Like BitingSarcasm and Obsessed with Edges said, the advertised "grits", "microns", and even abrasive materials of the various color compounds are all over the place. You can find all sorts of compounds on Amazon and Ebay but how is a person to know what they actually represent? How are we supposed to compare them? Some listings provide no information other than color! And what about production consistency? How do we know that the compound a company puts out today is the same as what they put out yesterday? Makes me wonder whether people doing industrial grinding / lapping / polishing use better-documented, maybe certified compounds and, if so, where I can get my hands on more information. And something else to muddy the picture: the substrate onto which a compound is loaded has an impact on the finish produced by that compound. A white compound loaded onto a sheet of metal may produce a different finish than the same compound loaded onto suede leather. Abrasive properties are a rather complex subject.

FYI, someone representing Sharpal on Amazon said, "SHARPAL green compound is comprised of Aluminum Oxide and Chromium Oxide at small grit size around 1 micron."
 
That blending of compounds, like the SHARPAL green w/AlOx & CrOx, is another big variable with these compounds and really complicates predicting how they'll work. Some mfrs of stick-type compounds will actually number them for a sequence - like '1' to be used first and '5' to be used last - which sometimes makes it easier if no other guidelines exist. But even then, some of the compounds in that numbered sequence may not be best for the given metal or steel being polished and would better be left out of a sequence for a particular type of metal, like hardened steel. Some compounds are better-suited for softer metals like brass or jewelry-grade metals (gold, silver), or even plastics, but will be ineffective or very slow to work on hardened stainless steels. And again, some stick-type compounds will also be labelled as best-used for particular metals. The aluminum oxide 'white rouge' I referenced earlier, a Ryobi compound at 2-5 microns, is labelled as best-used for stainless steel, for example. That's pretty common labelling for white aluminum oxide in particular.

Sequencing of compounds only by grit size is really only useful if all the grits used in the sequence are of the same type from a single mfr., with other variables like purity & uniformity of grit shape, hardness, toughness, etc. all being essentially equal. An example would be an all-diamond sequence as from DMT - their compounds sequence very seamlessly and are therefore very simple to predict results.
 
One way to avoid the uncertainty is to make your own emulsion. It's very simple to create one with chromium oxide. Just buy a jar of CrO2 powder and mix it with mineral or linseed oil until it forms a gooey paste. Pure CrO2 powder has a grain size between .2 and .5 microns, so it averages out to around .35 micron. I use that mixed with some .25 or .5 micron CBN emulsion. Works great on leather belts, but it would also apply very easily to a leather strop. Much easier to apply than those crayon stick compounds.
 
Blade Lab said:
One way to avoid the uncertainty is to make your own emulsion. It's very simple to create one with chromium oxide. Just buy a jar of CrO2 powder and mix it with mineral or linseed oil until it forms a gooey paste. Pure CrO2 powder has a grain size between .2 and .5 microns, so it averages out to around .35 micron. I use that mixed with some .25 or .5 micron CBN emulsion. Works great on leather belts, but it would also apply very easily to a leather strop. Much easier to apply than those crayon stick compounds.
Click to expand...
I've done it that way, mixed with mineral oil. Picked up the dry powder at a lapidary/rockhounding hobby supply. Nice thing about mixing it this way, with mineral oil, is that it can basically be 'painted' onto any material you choose, in a very even & dense coat. Just need to be very careful handling the dry powder so it doesn't get airborne - it's a hazard to the lungs and also makes quite the green-stained mess if it spills.

I liked it best as used on MDF, as seen in the green piece in the stack below. I used that for woodworking chisels, mainly.
DzJa0zK.jpg
 
Last edited:
You must log in or register to reply here.
Back
Top