I don't mean to try and have any final say on this stone here, or any other stone for that matter.
All I'm doing here is relating what I experienced.
I was interested in the Zulu Grey when I first heard of them last year.
The abrasive in Frictionite 00 hones came from Africa, and I thought it was kind of cool that someone was mining a whetstone for finishing razors there these days.
After some time, a very cool member of the board offered to lend me his Zulu Grey.
It was a nice treat to have someone just offer something like that out of the blue - you know who you are! And thank you very much for the opportunity.
Shortly before I returned the loaner stone, my own Zulu arrived and I redid my comparisons with that one also.
After a bit of email discussion with the Zulu Gray seller, and reading his website, I was able to learn the following about the Zulu Grey stone.
The ZG is an indurated sedimentary cherty siltstone/shale from the Pietermaritzburg ECCA group formation.
Doing a little digging around I came across this info;
Siltstones have particle sizes somewhere between 3-5 microns.
Size range for siltstone is 1/16 - 1/256 mm, the lower/finer end of that is 4 microns - or 4k.
Shale would have finer particles - but there is some overlap in particle-sizes between the two types of stone.
I don't see any shale-like tendencies - fissility, layering, etc. But - I'm not a geologist either.
Before I go on here; All of what I write about scratches and grit stuff means very little. I'm just interested in stones and I like to try and understand them better. Factually - a Surgical Black Ark maps out to around 1.4k and it kicks *** as a world-class finisher.
So - if the Zulu is a siltstone, it's particle size doesn't preclude it from being a finisher.
You'll notice that I didn't follow the methods of 'tests' that were done elsewhere. You'll also notice I don't assign a 'grit' to the Zulu. To me - doing so is about as useful as hanging boobs on a bull. To me, it doesn't make sense to do so when there are so many facts that obviate the assumed logic surrounding that practice. Finally - these are notes of my findings and not a 'test'.
I compared the scratch pattern off the polished side of the Zulu to those from MY 1k, 3k, 6k, 8k and 10k synthetic stones. The polished top of the Zulus I tested seem to be finer than my 6k, less fine than my 8 and 10k.
Bevel/edge inspection was done with a 15k B&L triplet, a 10x B&L doublet, and a 4x Schneider loupe.
I did use the Proscope at 50x a couple of times, but it wasn't necessary.
Variables and the human factor do exist and they do affect the final results. I make no claim to having done any of this work under any conditions that would/could be, even remotely so, connected or compared to to a battery of scientific tests.
Ok - what follows are my notes transcribed into some form of English that can, hopefully, be understood easily.
I chose a good razor that I know to take a great edge and I put it through a full Jnat progression (bevel to finish) and I then proved the edge with a shave.
Then - I cleaned up that edge and put it on the Zulu with approx 40 water only laps. Lost the undercut, edge seemed to be set back a bit.
Shave test - The Zulu finished edge was markedly less keen and smooth.
Same razor - Repeat same Jnat progression and shave test, but this time followed by slurry on the Zulu and diluting to water. Slurry was from Atoma 1.2k DN.
Shave test - better than the water-only trial but the edge was still very noticeably way less keen and smooth than the Jnat edge.
Same razor - Zero'd the edge, then brought to shave-ready with Coticule Dulicot and finished on an Thuringian. I proofed that edge with a shave, refinished on Zulu with water and another time with slurry - the result was less dramatic than with the Jnat scenario but the edge was still significantly less keen and smooth in both the Zulu & water and Zulu with slurry-finished edges.
I experimented with the Thuri-edge comparison a few different ways using a few different razors and honing styles/progressions - all results were the same.
Result - Thuri edge is keener/smoother.
Same razor - Straight Coticule edge - I pushed this edge on the Coti because that's how I normally handle them. I like the dead-velvet-squeegee edge sometimes, but I usually prefer a more lively blade with added keenness.
Anyway - same basic trials on the Zulu as above, shave test with the Coti edge and then a clean up followed by laps on the Zulu; first with water, then with slurry and dilutions.
Results - lost the coti feel on both the water-only and slurry laps. Lost sharpness on the water only laps, and it's hard to say what happened with the sharpness off the slurry laps. Might have been marginally better or a hair less.
I know that sounds weird but Coti edges are weird and it's hard to compare cutting efficacy of Coti edges sometimes. I'd would have to redo this test a bunch of times to know for sure.
Coti edge was smoother and more comfortable though.
Zulu used to finish an edge done on Synthetic Whetstones.
Took the edge on that same razor down to 1k, then 6k and 10k (all synthetic stones) - no real work, no Ninja efforts here. This edge was from a utilitarian honing season; done with a minimum of fuss and finesse.
Shave test was ok, almost good - not great. A bit harsh.
Then I zeroed the razor to 1k, then redid the progression up to 10k.
Then - onto the Zulu.
Water only laps. Hm... meh. Not sure anything was happening to be honest. Edge seemed to be set back. The undercut seemed to die off after 20 laps. It didn't remove the 10k scratches and it also left it's own scratch pattern on top; overall - the level of polish seemed to be diminished and I believe the Zulu retarded the 10k edge. I didn't bother shaving, I knew the edge was gone.
Again - zeroed the edge to 1k through 10k. After that, I went to the Zulu with laps on slurry. I used the Atoma 1.2k Nagura. Definitely something better going on now; there was a visible change in the action. The undercut came back and may have progressed.
I went a good distance with the slurry - the resulting scratch pattern was more even and the polish now seemed to be equal to or better than after the 10k.
Shave test was ok - smoother than just using the 10k to finish. Light tug on ATG though.
Again - zeroed the edge, went 1-10k on synths. After that I worked on the Zulu with slurry and diluted a bit but not to clear water.
Then - I cleared the stone and made a soap/water mix on the Zulu. After maybe 5-6 x strokes, I was able to see the undercut get better and after about 40 strokes it was pretty good.
Maybe I went 50-60 laps total. The undercut seemed to be as good as it was going to get. Not a radical undercut but still pretty good.
The resulting shave was much better. a bit not-smooth with some AS burn. It wasn't a killer shave but it was presentable.
Leaving the 10k and going to slurry on the Zulu, and then doing soap/water laps gave notable improvement over the straight 10k edge.
Zulu #2
Came with a slurry stone cut off the end of an 8x3" slab - the main stone is 6x3" the slurry is 2x3".
Came finished, wrapped, with extra labels. Nice touch.
I'll spare everyone the repetitive reading - I used the same razor and the tests were the same with two exceptions.
1.) The slurry stone - as difficult as it is to get a slurry going with it - did bring up a finer slurry that got the edge to a more refined state.
2.) I changed the final synthetic stone from a 10k to an 8k.
The Jnat edge outclasses the Zulu significantly.
When compared to an Escher-finished Coti edge, the keen-ness still isn't there, but it was sufficent.
Bottom line - the edge off the Escher was better; smoother/keener in a more comfortable way.
Compared to a straight Coti edge - Basically the same as with the other stone but the Zulu edge here was was keener/smoother than before. I do really have to call this a draw for keen but the Coti still wins on smooth/face-feel.
When used to finish after honing the edge to 8k on synthetics:
I swapped out the 10k used in the last test with an 8k.
The visual indicators tell me that the Zulu retarded the edge off the 8k initially.
Diluting the slurry seems to help it refine the edge but only to a point. I do not believe that this stone is all that great on just water laps.
In essence - my best results were from light slurry finishing followed by soap/water mix laps.
I preferred this edge to the one done with the 10k but that is probably due to starting off on finer slurry.
Overall impressions - I can get a good shaving edge with the Zulu. Nothing stellar but a decent/good utilitarian shave-ready edge. The edge is not harsh, but it's not really smooth like I've had from other stones. Not as keen either. Using the diamond nagura helps, but using the slurry stone is better. For some reason I don't feel the slurry breaks down at all, but diluting it did seem to help refine the edge further.
IMO - the Zulu is a superior stone to the Welsh Slates, a lot of other unknown-slates, and waaaaay better than any Chug I've owned. It's a good stone, but based on what I've experienced thus far, I don't consider it to be a high-end finisher.
All I'm doing here is relating what I experienced.
I was interested in the Zulu Grey when I first heard of them last year.
The abrasive in Frictionite 00 hones came from Africa, and I thought it was kind of cool that someone was mining a whetstone for finishing razors there these days.
After some time, a very cool member of the board offered to lend me his Zulu Grey.
It was a nice treat to have someone just offer something like that out of the blue - you know who you are! And thank you very much for the opportunity.
Shortly before I returned the loaner stone, my own Zulu arrived and I redid my comparisons with that one also.
After a bit of email discussion with the Zulu Gray seller, and reading his website, I was able to learn the following about the Zulu Grey stone.
The ZG is an indurated sedimentary cherty siltstone/shale from the Pietermaritzburg ECCA group formation.
Doing a little digging around I came across this info;
Siltstones have particle sizes somewhere between 3-5 microns.
Size range for siltstone is 1/16 - 1/256 mm, the lower/finer end of that is 4 microns - or 4k.
Shale would have finer particles - but there is some overlap in particle-sizes between the two types of stone.
I don't see any shale-like tendencies - fissility, layering, etc. But - I'm not a geologist either.
Before I go on here; All of what I write about scratches and grit stuff means very little. I'm just interested in stones and I like to try and understand them better. Factually - a Surgical Black Ark maps out to around 1.4k and it kicks *** as a world-class finisher.
So - if the Zulu is a siltstone, it's particle size doesn't preclude it from being a finisher.
You'll notice that I didn't follow the methods of 'tests' that were done elsewhere. You'll also notice I don't assign a 'grit' to the Zulu. To me - doing so is about as useful as hanging boobs on a bull. To me, it doesn't make sense to do so when there are so many facts that obviate the assumed logic surrounding that practice. Finally - these are notes of my findings and not a 'test'.
I compared the scratch pattern off the polished side of the Zulu to those from MY 1k, 3k, 6k, 8k and 10k synthetic stones. The polished top of the Zulus I tested seem to be finer than my 6k, less fine than my 8 and 10k.
Bevel/edge inspection was done with a 15k B&L triplet, a 10x B&L doublet, and a 4x Schneider loupe.
I did use the Proscope at 50x a couple of times, but it wasn't necessary.
Variables and the human factor do exist and they do affect the final results. I make no claim to having done any of this work under any conditions that would/could be, even remotely so, connected or compared to to a battery of scientific tests.
Ok - what follows are my notes transcribed into some form of English that can, hopefully, be understood easily.
I chose a good razor that I know to take a great edge and I put it through a full Jnat progression (bevel to finish) and I then proved the edge with a shave.
Then - I cleaned up that edge and put it on the Zulu with approx 40 water only laps. Lost the undercut, edge seemed to be set back a bit.
Shave test - The Zulu finished edge was markedly less keen and smooth.
Same razor - Repeat same Jnat progression and shave test, but this time followed by slurry on the Zulu and diluting to water. Slurry was from Atoma 1.2k DN.
Shave test - better than the water-only trial but the edge was still very noticeably way less keen and smooth than the Jnat edge.
Same razor - Zero'd the edge, then brought to shave-ready with Coticule Dulicot and finished on an Thuringian. I proofed that edge with a shave, refinished on Zulu with water and another time with slurry - the result was less dramatic than with the Jnat scenario but the edge was still significantly less keen and smooth in both the Zulu & water and Zulu with slurry-finished edges.
I experimented with the Thuri-edge comparison a few different ways using a few different razors and honing styles/progressions - all results were the same.
Result - Thuri edge is keener/smoother.
Same razor - Straight Coticule edge - I pushed this edge on the Coti because that's how I normally handle them. I like the dead-velvet-squeegee edge sometimes, but I usually prefer a more lively blade with added keenness.
Anyway - same basic trials on the Zulu as above, shave test with the Coti edge and then a clean up followed by laps on the Zulu; first with water, then with slurry and dilutions.
Results - lost the coti feel on both the water-only and slurry laps. Lost sharpness on the water only laps, and it's hard to say what happened with the sharpness off the slurry laps. Might have been marginally better or a hair less.
I know that sounds weird but Coti edges are weird and it's hard to compare cutting efficacy of Coti edges sometimes. I'd would have to redo this test a bunch of times to know for sure.
Coti edge was smoother and more comfortable though.
Zulu used to finish an edge done on Synthetic Whetstones.
Took the edge on that same razor down to 1k, then 6k and 10k (all synthetic stones) - no real work, no Ninja efforts here. This edge was from a utilitarian honing season; done with a minimum of fuss and finesse.
Shave test was ok, almost good - not great. A bit harsh.
Then I zeroed the razor to 1k, then redid the progression up to 10k.
Then - onto the Zulu.
Water only laps. Hm... meh. Not sure anything was happening to be honest. Edge seemed to be set back. The undercut seemed to die off after 20 laps. It didn't remove the 10k scratches and it also left it's own scratch pattern on top; overall - the level of polish seemed to be diminished and I believe the Zulu retarded the 10k edge. I didn't bother shaving, I knew the edge was gone.
Again - zeroed the edge to 1k through 10k. After that, I went to the Zulu with laps on slurry. I used the Atoma 1.2k Nagura. Definitely something better going on now; there was a visible change in the action. The undercut came back and may have progressed.
I went a good distance with the slurry - the resulting scratch pattern was more even and the polish now seemed to be equal to or better than after the 10k.
Shave test was ok - smoother than just using the 10k to finish. Light tug on ATG though.
Again - zeroed the edge, went 1-10k on synths. After that I worked on the Zulu with slurry and diluted a bit but not to clear water.
Then - I cleared the stone and made a soap/water mix on the Zulu. After maybe 5-6 x strokes, I was able to see the undercut get better and after about 40 strokes it was pretty good.
Maybe I went 50-60 laps total. The undercut seemed to be as good as it was going to get. Not a radical undercut but still pretty good.
The resulting shave was much better. a bit not-smooth with some AS burn. It wasn't a killer shave but it was presentable.
Leaving the 10k and going to slurry on the Zulu, and then doing soap/water laps gave notable improvement over the straight 10k edge.
Zulu #2
Came with a slurry stone cut off the end of an 8x3" slab - the main stone is 6x3" the slurry is 2x3".
Came finished, wrapped, with extra labels. Nice touch.
I'll spare everyone the repetitive reading - I used the same razor and the tests were the same with two exceptions.
1.) The slurry stone - as difficult as it is to get a slurry going with it - did bring up a finer slurry that got the edge to a more refined state.
2.) I changed the final synthetic stone from a 10k to an 8k.
The Jnat edge outclasses the Zulu significantly.
When compared to an Escher-finished Coti edge, the keen-ness still isn't there, but it was sufficent.
Bottom line - the edge off the Escher was better; smoother/keener in a more comfortable way.
Compared to a straight Coti edge - Basically the same as with the other stone but the Zulu edge here was was keener/smoother than before. I do really have to call this a draw for keen but the Coti still wins on smooth/face-feel.
When used to finish after honing the edge to 8k on synthetics:
I swapped out the 10k used in the last test with an 8k.
The visual indicators tell me that the Zulu retarded the edge off the 8k initially.
Diluting the slurry seems to help it refine the edge but only to a point. I do not believe that this stone is all that great on just water laps.
In essence - my best results were from light slurry finishing followed by soap/water mix laps.
I preferred this edge to the one done with the 10k but that is probably due to starting off on finer slurry.
Overall impressions - I can get a good shaving edge with the Zulu. Nothing stellar but a decent/good utilitarian shave-ready edge. The edge is not harsh, but it's not really smooth like I've had from other stones. Not as keen either. Using the diamond nagura helps, but using the slurry stone is better. For some reason I don't feel the slurry breaks down at all, but diluting it did seem to help refine the edge further.
IMO - the Zulu is a superior stone to the Welsh Slates, a lot of other unknown-slates, and waaaaay better than any Chug I've owned. It's a good stone, but based on what I've experienced thus far, I don't consider it to be a high-end finisher.
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