How the heck does Thuringian slurry work?

[Frank Shaves]

I have two Thuringians: 1) a small yellow, green, blue piece I bought from Peter, and 2) a 5 x 2.5 mottled green stone.

I have been using slurry starting about the thickness of 1 to 2 percent milk that I gradually dilute until it's mostly water. I am only reaching sharp and smooth about once per three/four tries. I tried thicker slurry on the first stone one time and ended up with coarse scratch marks.

The few sharp and smooth edges I have gotten have been delightful.

When I do the same thing with my Nakayama Asagi and Ozuku, it's sharp and smooth every time.

Is Thuringian slurry like JNAT slurry raised with a DMT (just fine slurry that speeds up the honing process) or does it contain some secret sauce that depending on the dilution can dull your edge or are these stones just playing with my mind?

Surprisingly, I cannot find much information about how Thuringian slurry works.

 

[C FrankC]

My experience is that the slurry from my J-Nat's breaks down as I hone and creates finer abrasiveness as I continue to hone, (up to a point).
The slurry from my Thuri's needs to be diluted as I find that it does not significantly break down and if I use slurry, I always dilute it and then finish on a clean stone without slurry.
I always use compatible slurry stone to prep the surface and generate slurry on my Thuri's, I think that a diamond plate leaves the surface a bit to coarse for my liking and the slurry may also be affected in a negative way coming from a diamond plate.
I can go from post bevel set to finish on some of my J-Nat's with properly generated slurry and allowing enough break down to said slurry during honing.
With my thuri's I always use them as just finishers with or without thin slurry depending on what they need to finish, generally coming off a Coti or a 10>12K synth or equivalent level.

 

[Frank Shaves]

Since writing the OP, I honed two more razors and meh. Next, I am going to hone one of the razors on my 8k and 12k (to get back to a known good place), and then mimic what @gary haywood does on the Escher in this video - 100 laps with slurry:

Then I am going to take the same razor back to 8k followed by the 100 laps on the Thuri with slurry.

 

[Empire straights]

LIKE A CHARM! *crickets* Thank you! I'll be here all week!

 

[Empire straights]

I've decided I like mine too finish with slurry, more than on any other stone. I finish my green one at 1% and only add water as it dries. I love my green thuri and it puts insanely sharp edges on my razors but still very smooth. Even more so than my ark.

 

[SliceOfLife]

Thuri particles are as fine as a razor finisher needs from the get go. I think the main reason slurry was suggested in old labels was not so much to increase abrasion OR to increase fineness. I think it was to change how the razor felt on the stone... even it out almost... so users wouldn't hit a dry patch if their water was pooling/etc. I think functionally it affects how the hone hits the razor very very little. It's more of a quality of life thing for honers. It also probably served to convince more people to keep it free of oil. Yes the labels also warn against oil, but guys who've used oilstones their whole lives may well ignore that... having detailed instructions on how the stone SHOULD be used, with a process that has an element that rules out oil (slurry on oil is self-defeating), they probably kept a few more stones oil-free than just "Don't Use Oil!" labels would have.

Also Thuri's can be quite soft and it's easy to scratch them... heck a speck of dust getting pinned in the razor hollow at the spine can do it. Slurrying up the stone helps prevent scratches from accumulating. Could be part of the reasoning too?

Generally I can think of a bunch of good reasons for using slurry with Thuringians... I've never noticed the SHAVE got any better or worse with slurry vs without, so I doubt performance was the real reason.

 

[rideon66]

I have two points on Thuri slurry. First as mentioned above the slurry acts kind of like oil to change the viscosity of the water and give you more control. This can work on other stones too with a Thuri slurry stone. Second if you rub the entire rock every time with the slurry stone you are basically lapping it every time so it will stay flat.

 

[Empire straights]

Thuri particles are as fine as a razor finisher needs from the get go. I think the main reason slurry was suggested in old labels was not so much to increase abrasion OR to increase fineness. I think it was to change how the razor felt on the stone... even it out almost... so users wouldn't hit a dry patch if their water was pooling/etc. I think functionally it affects how the hone hits the razor very very little. It's more of a quality of life thing for honers. It also probably served to convince more people to keep it free of oil. Yes the labels also warn against oil, but guys who've used oilstones their whole lives may well ignore that... having detailed instructions on how the stone SHOULD be used, with a process that has an element that rules out oil (slurry on oil is self-defeating), they probably kept a few more stones oil-free than just "Don't Use Oil!" labels would have.

Also Thuri's can be quite soft and it's easy to scratch them... heck a speck of dust getting pinned in the razor hollow at the spine can do it. Slurrying up the stone helps prevent scratches from accumulating. Could be part of the reasoning too?

Generally I can think of a bunch of good reasons for using slurry with Thuringians... I've never noticed the SHAVE got any better or worse with slurry vs without, so I doubt performance was the real reason.

To me la lunes and thuris both have a little less bite to the edge of they finish with light slurry(or lather). Plain water with either and the get so sharp they try to dig in a little with any pressure.

 

[haggis]

I've only recently got a thuri to try so experience n=1, used with water only. The suggestion that slurry would affect the feel in a positive way seems rather plausible. I'm not sure 'unpleasant' is the right word, but the the feel on water was not, shall I say, relaxing. Despite my reservations about the feel I have to say the resulting shave was fine, even excellent. My example did not come with a slurry stone. Would a light atoma 1200 slurry be an ill-adivsed way to try it? Lather also sounds easy.

 

[SliceOfLife]

Atoma 1200 should be fine. Thuri's are pretty forgiving about surface condition.

 

[H Brad Boonshaft]

Small hard Arks make great slurry stones for slates and coticules. Small pen knife and slip stone are abundant and inexpensive.

 

[thp001]

Slurry in itself is detrimental to the creation of an apex (an apex defined as two planes intersecting at a theoretically perfect point). When you hone on a stone with slurry, the particles which are suspended in the lubricant (water, oil, etc) have a large probability of moving into the apex as they do away from the apex. You are engaging in what is known as 3-body abrasion.

Now on a Thuringian the particulates are going to be so small that any impact to the apex will not severely set back the sharpness but could serve to tame an apex that has a high enough degree of sharpness that it wants to bite into skin.

The speed one sees on a stone after slurrying isn't for the most part the slurry but the fact that you have exposed fresh abrasive on the surface of the hone which is going to be better at cutting than the worn abrasive it previously had. One caveat to this would be using a slurry with much coarser particles than the hone where the magnitude of the particle size differences dwarf other factors.

 

[Empire straights]

I've only recently got a thuri to try so experience n=1, used with water only. The suggestion that slurry would affect the feel in a positive way seems rather plausible. I'm not sure 'unpleasant' is the right word, but the the feel on water was not, shall I say, relaxing. Despite my reservations about the feel I have to say the resulting shave was fine, even excellent. My example did not come with a slurry stone. Would a light atoma 1200 slurry be an ill-adivsed way to try it? Lather also sounds easy.

I'm not the biggest fan of plain water, and +1 for hard ark slurry. Hit it with the 1200 really fast to waken it up Little if it's not slurrying to your liking.

 

[Gamma]

Using slurry on an Escher has repeatedly shown me that it's a 'non enhancement' type of thing. It is not like a Jnat in that regard. Best I can figure is that it helps to clear/prep the stone's surface, and provide a honing medium with higher viscosity. I have not seen any friability, break down, or edge-refinement as a result of using it or not. I will usually opt to give the working surface a quick pass or two from a slurry stone, just for the alteration in the feedback though. I like the cushy-er feel when there's a ghost in the puddle.

 

[Steve56]

When I do the same thing with my Nakayama Asagi and Ozuku, it's sharp and smooth every time.

I think that you have answered your own question there Frank !

 

[Frank Shaves]

Much better! For this morning's shave, I did the following with a test razor:

1. 8k, 12k, linen and leather
2. Passed HHT and shaving my cheek
3. 100 laps on my 5 x 2.5 Thuri with slurry using light pressure (as per Gary's video), linen, leather
4. Passed HHT and shaved great

I will next do the same thing with a second razor using my smaller Thuri, and then I will try going directly from 8k to a Thuri.

I would like to think that the case is now closed.

 

[Frank Shaves]

Shift in topic.

We now know that JNAT slurry increases abrasiveness, we can dilute it as we finish the step in the progression, and we can raise slurry from the base stone and optionally from separate slurry stones with different levels of particle size (grit) than the base stone.

We also know that Thuri slurry provides cushion and has less effect on abrasiveness than JNAT slurry.

When raising slurry on a Coticule, does the thickness of the slurry only effect the abrasiveness of the slurry or does the thickness also effect the particle size of the slurry. For example, when thick Coticule slurry is diluted does the particle size increase?

 

[rideon66]

Shift in topic.

We now know that JNAT slurry increases abrasiveness, we can dilute it as we finish the step in the progression, and we can raise slurry from the base stone and optionally from separate slurry stones with different levels of particle size (grit) than the base stone.

We also know that Thuri slurry provides cushion and has less effect on abrasiveness than JNAT slurry.

When raising slurry on a Coticule, does the thickness of the slurry only effect the abrasiveness of the slurry or does the thickness also effect the particle size of the slurry. For example, when thick Coticule slurry is diluted does the particle size increase?

With coticules it is garnet size and as these should not be broken down they will remain the same size throughout. Now as you go to water only on a coticule you are tending to go to the ones traped in the surface so are only hitting the tops. As you dilute you are only lessening the amount. As I understand it.

 

[rideon66]

I should add to my above it is about garnet count and size. Which is why dilution works.

 

[SliceOfLife]

@Frank Shaves I always love seeing Thuris with that brassy speckling in them. I've got one that's absolutely coated in that stuff on one side and took awhile to convince myself it was a Thuri despite it performing exactly like one, having the right sawmarks, etc.