Another strop thread....

[HeavyHanded]

A side effect of sanding the strop when dealing with spray-on emulsions might also be to increase the attachment/penetration into the leather, giving it a bit less mobility.

Grease sticks come with their own binder and that keeps them reasonably fixed in place. The smoother the surface, the less a loose grit will stay put, greatly diminishing its effect. Similar to roughing up a hardwood lapping board as opposed to using one that's been polished smooth.

On really hard leather it might even reduce the effective footprint at the microscopic level, which would increase the rate of polish as well.

 

[stitchawl]

A side effect of sanding the strop when dealing with spray-on emulsions might also be to increase the attachment/penetration into the leather, giving it a bit less mobility.

Grease sticks come with their own binder and that keeps them reasonably fixed in place. The smoother the surface, the less a loose grit will stay put, greatly diminishing its effect. Similar to roughing up a hardwood lapping board as opposed to using one that's been polished smooth.

On really hard leather it might even reduce the effective footprint at the microscopic level, which would increase the rate of polish as well.

So you don't imagine that the abrasive particles embed themselves part-way into the leather? Hmmm......

Have you ever taken powdered Chromium Oxide pigment used for making barn paint and sprinkled on a flat board? Blow off the excess, brush away any remaining, and the board stays green. Try wiping it off. Doesn't work. The board stays green. That's Chromium Oxide that's embedded itself into the pores of the wood and into the wood fibers themselves. And wood is harder than leather.

In my mind, if I want to get a clear image of what's going on at the microscopic level, I enlarge everything.
.5 micron grit becomes the size of a grain of builder's sand (not round sea sand.) And the pores in the leather become putting green holes that the grit can actually get lost into. After all, the pores are the size of a hair, right? About 20-40 microns. And the grit is sharp enough and hard enough to bite into the leather, and not really move very much at all. Some, for sure. But not much.

Then I think about flattening a Japanese water stone with that same sand, sprinkling it onto a smooth cement paver. Then by just rubbing the water stone over the loose sand on the paver, the water stone 'somehow' manages to get abraded enough to flatten it, without any need to secure the sand to the paver below.

So how much is sanding leather really accomplishing? Again, for me with my 10-15 strokes, not much at all.
For someone doing 100 strokes, perhaps they are saving 2 or 3?
For someone doing 1,000 strokes on a strop, they might save 15 seconds of stropping, but having spent several minutes sanding the strop...

Is it different? Yes.
Is the difference worth the effort? In my opinion, no. It's not.
Is it worth trying? Sure. There's nothing to lose but a little bit of time.


Stitchawl

 

[ToddS]

I should clarify; by more effective I meant a superior edge, not faster.
However, I don't have systematic results to back up that observation.

My experience has been that pasted-strops do their thing in about 5 laps, and not much changes by 500. I agree, speed is of no consequence.

Here are a couple of images of strop leather prepared from vegetable tanned Horween.

Sanding will break up those fibers, leaving a microscopically "fuzzy" surface.

 

[HeavyHanded]

So you don't imagine that the abrasive particles embed themselves part-way into the leather? Hmmm......

Have you ever taken powdered Chromium Oxide pigment used for making barn paint and sprinkled on a flat board? Blow off the excess, brush away any remaining, and the board stays green. Try wiping it off. Doesn't work. The board stays green. That's Chromium Oxide that's embedded itself into the pores of the wood and into the wood fibers themselves. And wood is harder than leather.

In my mind, if I want to get a clear image of what's going on at the microscopic level, I enlarge everything.
.5 micron grit becomes the size of a grain of builder's sand (not round sea sand.) And the pores in the leather become putting green holes that the grit can actually get lost into. After all, the pores are the size of a hair, right? About 20-40 microns. And the grit is sharp enough and hard enough to bite into the leather, and not really move very much at all. Some, for sure. But not much.

Then I think about flattening a Japanese water stone with that same sand, sprinkling it onto a smooth cement paver. Then by just rubbing the water stone over the loose sand on the paver, the water stone 'somehow' manages to get abraded enough to flatten it, without any need to secure the sand to the paver below.

So how much is sanding leather really accomplishing? Again, for me with my 10-15 strokes, not much at all.
For someone doing 100 strokes, perhaps they are saving 2 or 3?
For someone doing 1,000 strokes on a strop, they might save 15 seconds of stropping, but having spent several minutes sanding the strop...

Is it different? Yes.
Is the difference worth the effort? In my opinion, no. It's not.
Is it worth trying? Sure. There's nothing to lose but a little bit of time.


Stitchawl

Ah, but the devils in the details. I once did an experiment with a boiled piece of veg-tanned leather, applied compound to the smooth side. Was able to wipe of enough of the compound that I could see no meaningful trace at 40x or even 100x. For sure the fact that a binder was available to help remove the abrasive played a role, but was an interesting test anyway. This is an extreme example, but sanding the leather did help it hold the compound more reliably.

I've also done plenty of experiments that showed a world of difference between using slurries and loose powders on smooth sanded clear maple, and maple that had been scuffed up with a hacksaw blade. Night and day how well it works.

In your analogy I'd imagine how open the cell structure of the board that's being sprinkled will have a big impact. Likewise a huge difference between the loose sand on a paver and on polished granite or plate glass, especially if the abrasive isn't very friable. I am also aware of folks using "sharpening boards" with loose grit, and have done some noodling with those as well, but are generally made from a fairly open cell wood type - huge difference between maple and red oak. A big difference between using loose dry abrasive powder on a sheet of paper, and using it with a bit of oil or other binder, even though the paper gets plenty colored either way.

I'm imagining the sanding of the leather actually makes it less smooth not more, though maybe more uniform in terms of how its formation compresses. I have to imagine the specific leather sample plays a big role in the outcome. I don't do much with leather anymore anyway, so its all speculation - if I had a strop that was working well, I wouldn't change a thing.

 

[Obsessed with Edges]

Those images^ are an eye-opener. Thanks for posting that, Todd. :thumbup:

I've often wondered what the surface of leather really looks like, at the microscopic level. It's not hard to see how some very fine compounds could settle into & be embedded in it. To me, those images also shed light on how bare leather could be very effective in stripping away the loose, tiny remnants of burrs & such from an edge; all of those fibers snagging anything ragged and pulling it away, or at least straightening them.

I've usually viewed the sanding of leather like working up the 'nap' in a dense shag carpet. When I've sanded it, mainly to make it easier to take & hold stick/crayon-type compounds, I've eventually noticed the 'nap of the rug' will flatten and settle again, with some use. Strops I've sanded always go back to being smooth and even shiny. The main benefit I've seen from sanding, is it makes it easier to more evenly distribute the compound onto (and into) the leather. I think that's also contributed to the effectiveness of the leather in stropping, due to the denser and more uniform coverage of compound in the surface of the leather.

With a dry, powdered compound, I haven't felt as much need to sand the leather prior to rubbing the compound onto it. As stitchawl mentioned, the green compound in particular makes it easy to see how easily the compound works itself into any surface that's even microscopically porous, as it immediately clings to and stains anything it contacts. Green compound is the messiest I've used in powdered form, for that reason. I've always applied it to my strops over the bathroom sink, and even the tiniest bits of it will even stain the porcelain glaze on the sink itself.

BTW, it'd be great to see similar images of the same (or very similar) leather, with some green compound applied. I'd be interested to see how the particles embed into the leather.


David

 

[stitchawl]

Thanks for those images, Todd! Nice to see. I too would love to see them 'after' the application of a compound!

No doubt there will be a difference. But I question the degree when used for stropping.
I guess it would make a bigger difference for those who strop thousands of strokes rather than 10.

.............I've usually viewed the sanding of leather like working up the 'nap' in a dense shag carpet. When I've sanded it, mainly to make it easier to take & hold stick/crayon-type compounds, I've eventually noticed the 'nap of the rug' will flatten and settle again, with some use.

With a wax binder, I'd guess that happens almost instantly.

With a dry, powdered compound, I haven't felt as much need to sand the leather prior to rubbing the compound onto it. As stitchawl mentioned, the green compound in particular makes it easy to see how easily the compound works itself into any surface that's even microscopically porous, as it immediately clings to and stains anything it contacts. Green compound is the messiest I've used in powdered form, for that reason. I've always applied it to my strops over the bathroom sink, and even the tiniest bits of it will even stain the porcelain glaze on the sink itself.

There is an apartment in northern New England that still has a floor with a greenish color cast to it, 40 years after the fact... My first experience using powdered Chromium Oxide...


Stitchawl