Thread: A quick slurry study

I get to spend some time on an SEM from time to time, so I figured I'd snap a few photos of the grits of some finishing stones to see how they look like before and after honing. I am not aware of other such studies so I figured it might be interesting for you guys.

I got a new Nakayama which I used to hone a Bismarck, and decided that will be the first stone to investigate. I collected samples of the slurry freshly raised with Atoma 1.2k diamond plate, and slurry after the razor was finished. I really wanted to see how much of a break down the slurry does while working it with a razor. Here are the results for the particular stone.

The stone: Iwasaki Choice Nakayama


Raw slurry:



Heavily worked slurry:


Today I had more time on the SEM so I decided to snap some photos on Escher slurry.
I had two samples raw slurry , freshly raised with Atoma diamond plate, and worked slurry, right after the razor was honed.

Escher raw slurry:



Escher worked slurry:



My impressions from the images:

Jnats slurry has flaky structure, and the break down happen by flaking off, as well as braking down. The flatness of the grit explains the shallow scratch pattern left on the bevel.

Escher looks very similar to Jnat, the grit is flaky although to my eye not exactly the same type.

What do you guys think?

IMO, the sample size is waaaay to small to say anything. I'd be curious about average particle size before and after, which would require a large sample size.

From the photos, it looks to me like the average particle size of the Jnat is the same before and after with the exception of the one big piece. It looks to me like the Escher's average size is the same before and after too, again, with the exception of one big piece.

I think the structure of the grit shows how the break down happens, its by reducing thickness mainly. There is also size break down but IMHO before that happens the bevel is already smooth enough.

Given that both a these are superlative finishers, it suggests that grit size is considerably larger than many claim in the worked slurrries.i.e. 30k etc. Thanks for sharing great images. Also, it confirms my personal preference for harder stones as they release particles at a slower rate making it possible to control the particle size at the finish. Fun and useful info.

Originally Posted by mainaman

I think the structure of the grit shows how the break down happens, its by reducing thickness mainly. There is also size break down but IMHO before that happens the bevel is already smooth enough.

I don't understand what you mean. As I understand it, "thickness" of slurry is the ration of hone particles to water particles, while size is the size of the slurry particles. To me, the average size appears about the same in your before and after photos, but I also think there is not enough data to find a trend; it seems you disagree and think the average size is smaller after.

In your post you say "it's by reducing thickness mainly." Can you elaborate on what you mean by that? Because as I understand it, the thickness of the slurry is reduced by adding water.

Originally Posted by holli4pirating

I don't understand what you mean. As I understand it, "thickness" of slurry is the ration of hone particles to water particles, while size is the size of the slurry particles. To me, the average size appears about the same in your before and after photos, but I also think there is not enough data to find a trend; it seems you disagree and think the average size is smaller after.

In your post you say "it's by reducing thickness mainly." Can you elaborate on what you mean by that? Because as I understand it, the thickness of the slurry is reduced by adding water.

Dylan,
I did not mean particles to water ratio, this is not what I was looking at. I meant that each grit particle breaks down in how thick it is by flaking off.
Jnats have layered structure, like book pages, which from the pics goes all the way to the grit particles.

鋸-鉋-鑿　（Nokogiri-Kanna-Nomi）
a few entries down


Is there any metal in the after use image?

Originally Posted by kevint

鋸-鉋-鑿　（Nokogiri-Kanna-Nomi）
a few entries down


Is there any metal in the after use image?

I took the samples from the supernatant in the solution, all metal particles should have been in the crud on the bottom of the vial.

You need to be very careful making conclusions here. The pics are interesting but by themselves mean little. You have to know the particular chemical brakdown of the minerals making up the rock and their characteristics which will determine the result. You also have to analyze the slurry to see what you have there.

Methinks using the same diamond lapping plate will cause the diamond to break off similar particales of the hone no matter what it is since the diamond is so much harder than the hone no matter the type.

Originally Posted by thebigspendur

You need to be very careful making conclusions here. The pics are interesting but by themselves mean little. You have to know the particular chemical brakdown of the minerals making up the rock and their characteristics which will determine the result. You also have to analyze the slurry to see what you have there.

Methinks using the same diamond lapping plate will cause the diamond to break off similar particles of the hone no matter what it is since the diamond is so much harder than the hone no matter the type.

I agree with all you said, the conclusion is totally my personal opinion that could very well be wrong.
I also made a mistake and typed that I used Atoma for the Escher , in fact I used my 6x1" Escher as slurry stone.
Again all the conclusions are totally my own attempt to explain how I think things work, a speculation on my part not a fact.