Black Compound on a Strop?

[dannerman]

I am curious why someone would want a black compound on a strop. I love the green compound and it does everything that I need...or does it? The black compounds are generally a lot courser. Thoughts?

 

[dw32005]

I like to go from white to green. I've. Ever used the black, interested to hear about it.

 

[bucketstove]

Hi,
You would use it for the same reason as using any kind of strop
which are
+ you don't have a stone in that grit but you have compound
+ flexibility for angle matching or apex rounding

Yesterday I stropped using a mix of 100-~320grit to deburr a serrated blade

 

[Steel_Drake]

I am curious why someone would want a black compound on a strop. I love the green compound and it does everything that I need...or does it? The black compounds are generally a lot courser. Thoughts?

This is going to be a bit tricky to explain:

Basically, when you apply particulate abrasive stropping compounds to a compressible surface (e.g. leather, balsa wood) the size of the abrasive particles will not correspond to how coarse or fine a finish they will leave on a knife apex. This is because the abrasive particles get pressed into the compressible surface of the strop, meaning they cannot cut to their maximum scratch depth, and, because the surface is compressible it also cannot press into the knife edge with the same amount of force (and therefore pressure) a solid abrasive would, thereby additionally reducing the scratch depth. This effect becomes more and more severe as the size of the particulate abrasive particle increases up until the abrasive particles get so large that they stop sinking so far into the strop surface (which begins to occur above 30 microns).

In practical terms, this that a 16 micron CBN emulsion on balsa wood will still produce an apex finish with extremely high push-cutting sharpness (high enough to very easily do crossgrain pushcuts on newsprint), while still having enough slicing aggression to cleanly slice through folded over paper towel without slipping.

That 16 micron CBN on balsa will also cut fast enough to create and touch-up (back to ~100% of initial sharpness) a convex microbevel for some time between full sharpenings on a light use EDC knife, and because the 16 micron CBN on balsa leaves some slicing aggression, there is no danger of "over stropping" the apex.

For example, my Spyderco Spydiechef has a ~10 degree per side edge bevel that was shaped to 1000 grit and then a 16 micron CBN on balsa convex microbevel was applied. You can see below that the 16 micron CBN on balsa finish produces a semi-mirrored edge bevel, despite how "coarse" 16 micron CBN emulsion is (in theory) as this convex microbevel has been touched up repeatedly over the last week or so:

 

[hiwa]

I bought a tube of Dico brand black I've been experimenting with on a leather strop that's glued to wood.
I find that it is a little more aggressive than green compound. Another thing I noticed it is more "grabby" as I pull my knife along it , so the feel is different when stropping.

I use Flexcut gold on some strops and diamond paste also. I don't find the black to be of too great a benefit. If I need to take more metal off , I'm better to go back to the stone.

If I had to pick only one, I'd probably stick with my Veritas green compound.