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Difference in jnat dmt slurries

So i have a well worn out dmt 325 card and a dmt 1200 6×2 stone. I have tried both for generating slurry and the dmt 1200 sticks to the stone like crazy and tends to create a dark grey/black slurry. I am using a shobudani.

The dmt 325 slurry is much easier to generate and is a lot lighter... what gives..

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That's an interesting observation. Presumably the slurry from the finer dmt would be finer and I would propose that the finer slurry is reflecting light differently. I have always assumed that as the slurry was darkening with use that it was because of the steel in the swarf. Your observation suggests that some of the darkening may be that the slurry is just getting finer.
 
The slurry generated by my dmt 1200 (which is super worn out) is almost black before i even take a razor to it. It also appears to be quite silky whereas the dmt 325 slurry is light grey before taking a razor to it and gets darker as i hone on it.

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The dmt 1200 is pretty much done. Not much left on there

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Hello twoods

But just a few years ago the idea of using a diamond plate as a diamond nagura on these valuable Jnat stones would have drawn pages of scorn from a few activist's who claimed that in Japan this was never done, as a reason why we should not do it. Here we are now out of the "old" stone age.

The DMT do have a problem with suction created between the stone and the diamond plate, the Atoma brand has less of a problem but still their #1200 can get stuck too if you try and raise too much slurry, when you do that the area between the embedded diamonds fills with this semi-liquid slurry forcing out any air bubbles thus creating suction. I found that if you use the plate towards one end of your stone, slide, do not lift, but slide the plate off the stones edge and then raise more slurry towards the other end of your stone you can double the amount of slurry you get. With the DMT #1200 you will have to be satisfied with just the amount of slurry that you can draw, and no more.

I say, don't lift the plate off the stone because if you force and lift and pry the plate off the stone the suction can pull larger grit bundles off the stone which can foul your edge. I think that you will find that a light touch with your DMT 325 will give you a slurry that soon breaks down to a level fine enough for razors. Using a diamond plate of any grade will provide you with slurry resembling bundles of grit that in a general sense represent the diamond plates grit rating. The grit bundles arel tentatively held together by the stones weak clay binders. With a Jnat finishing stone these bundles will under pressure begin to melt as the clays soften. Because the grit rating of a #400 diamond plate will give you a coarser slurry component than a #1200, you can tune your honing progression taking this into consideration.

I suggest you switch to the Atoma brand products.

Alex
 
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Yes! Atoma much less sticking. I use the 1200. Never fails but nice and easy as was mentioned. CKTG had a slip stone for less than the price of the full plate. Although imo if you spring for it you won't ever have to replace it.
 
Yeh I probably will eventually pick one up. For now the dmt 325 card seems to be doing well. I am also getting a tsushima nagura today. I plan on going 2k to 5 k shapton pro to tsushima and finish on a few tomos.

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The darkening is very likely nickel plating that is abrading away while you produce slurry. Bad juju for your diamond plate. I additionally and in agreement with the others suggest switching to an Atoma plate if you want to use higher grit like 1000+.
 
Hello twoods

But just a few years ago the idea of using a diamond plate as a diamond nagura on these valuable Jnat stones would have drawn pages of scorn from a few activist's who claimed that in Japan this was never done, as a reason why we should not do it. Here we are now out of the "old" stone age.

The DMT do have a problem with suction created between the stone and the diamond plate, the Atoma brand has less of a problem but still their #1200 can get stuck too if you try and raise too much slurry, when you do that the area between the embedded diamonds fills with this semi-liquid slurry forcing out any air bubbles thus creating suction. I found that if you use the plate towards one end of your stone, slide, do not lift, but slide the plate off the stones edge and then raise more slurry towards the other end of your stone you can double the amount of slurry you get. With the DMT #1200 you will have to be satisfied with just the amount of slurry that you can draw, and no more.

I say, don't lift the plate off the stone because if you force and lift and pry the plate off the stone the suction can pull larger grit bundles off the stone which can foul your edge. I think that you will find that a light touch with your DMT 325 will give you a slurry that soon breaks down to a level fine enough for razors. Using a diamond plate of any grade will provide you with slurry resembling bundles of grit that in a general sense represent the diamond plates grit rating. The grit bundles arel tentatively held together by the stones weak clay binders. With a Jnat finishing stone these bundles will under pressure begin to melt as the clays soften. Because the grit rating of a #400 diamond plate will give you a coarser slurry component than a #1200, you can tune your honing progression taking this into consideration.

I suggest you switch to the Atoma brand products.
 
I would be interested in hearing from someone with both 325 and 1200 newish diamond stones to rule out the nickel contamination. Not saying that the nickel is not the cause, but I would be interested in hearing if finer slurry just naturally appears darker.
 
Oh, about the blackness of the swarf with the finer DMT. The blackness is in contrast to the clay in the slurry, the swarf concentration from the #1200 might be the same percentage, but as you said you have less slurry from your #1200 and the over abundance of #325 slurry masks the amount of swarf in the slurry There swarf content most likely in each slurry is similar. With the #325 slurry some buffering is happening with the cushion of the mass of the slurry, but be assured, the cutting of steel is still happening and probably somewhat more aggressively with the coarser DMT.

Alx
 
I would be interested in hearing from someone with both 325 and 1200 newish diamond stones to rule out the nickel contamination. Not saying that the nickel is not the cause, but I would be interested in hearing if finer slurry just naturally appears darker.

I have both plates (well 400 and 1200) that are Atoma and the slurry color is very similar as long as excessive thickness of slurry isn't allowed to build up - at which point the slurry darkens. Pretty sure it's nickel plating being abraded - may even be aluminum after the nickel is gone.
 
Oh, about the blackness of the swarf with the finer DMT. The blackness is in contrast to the clay in the slurry, the swarf concentration from the #1200 might be the same percentage, but as you said you have less slurry from your #1200 and the over abundance of #325 slurry masks the amount of swarf in the slurry There swarf content most likely in each slurry is similar. With the #325 slurry some buffering is happening with the cushion of the mass of the slurry, but be assured, the cutting of steel is still happening and probably somewhat more aggressively with the coarser DMT.

Alx

Alex, he was referencing the O.P. - in which the slurry darkening was occurring BEFORE honing any steel. Just while it was being generated with the diamond plate.
 
Alex, he was referencing the O.P. - in which the slurry darkening was occurring BEFORE honing any steel. Just while it was being generated with the diamond plate.
Yeh this is before honing with a razor

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As an aside regardingthe swarf darkening the slurry: yes this is the steel coming off the razor. If you hone long enough on the same slurry, on some stones it will actually start to oxidize and turn a little orangeish.
 
I have both plates (well 400 and 1200) that are Atoma and the slurry color is very similar as long as excessive thickness of slurry isn't allowed to build up - at which point the slurry darkens. Pretty sure it's nickel plating being abraded - may even be aluminum after the nickel is gone.
Thank you!
 
I have both plates (well 400 and 1200) that are Atoma and the slurry color is very similar as long as excessive thickness of slurry isn't allowed to build up - at which point the slurry darkens. Pretty sure it's nickel plating being abraded - may even be aluminum after the nickel is gone.
I have the same experience. I lap my jnats with Atoma 140,400 and then 1200 and the slurry looks the same color wise.
 
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