What IS an India stone, and can one be made?

[m.wesolowski]

I guess I'll make my first post after extensively reading through this forum regarding sharpening stones.

I've been trying to find a suitable sharpening stone in AlOx for sharpening straight razors, pocket knives, kitchen knives, wood working tools... so basically all kinds of blades really. My first idea was going with the norton combination india stone, which would give me a scratch pattern of something around 600# when applying light pressure, but also that keeps flat for a long time and has a decent material removal. Seemed to be a good call, most wood workers have used it as a bench stone the best part of a century if not more, the only problem is that it's unthinkable to get one where I live.

AlOx stones over here (Brazil, for context) are readily available, some Norton Crystolon (SiC) stones are even made here and shipped to the US, as mentioned in this post, Carborundums (SiC) are also made here (same factory as the Norton ones, if I'm not mistaken, given both of them belong to the Saint-Gobain group) but those I think are just for internal distribution. Thing is, they are all made to be used with water, or at least that's the advertised intention. As said in the aforementioned post, they don't "pre-oil" the stones (or, as we say, season it) with petroleum jelly as they seem to do with Norton's patented India oil stones, their porosity also seems to be quite high due to being required to release a slurry in water, which is not the case for oil stones.

Considering that the combination India stones in-land are prohibitively expensive (around 350BRL on the local amazon page) and importing a mexican-produced benchstone from the US would not only be prohibitively expensive (something in the bouts of 125BRL) but would incur the importation problems that I don't want to deal with.

So I got to thinking: what is the structure of sharpening stones and what makes them what they are, exactly? Yes, there's porosity, there's binder and there's the abrasive, and the difference in between them is basically the kind, quality and ratio of those. From what I read, India stones are densely packed #400 AlOx with a glass matrix, and the few pores it has are filled from the factory with petroleum jelly so that the thin mineral oil floats on the surface instead of just falling through the stone. To my understanding, this makes the stone very wear resistant but also slows the process of sharpening since the grit is not released in a slurry that will be rolled around between the metal and the stone.

With these accounted for, I've set out to get a stone to my needs, which would be a proper combination India oil stone but which I cannot get due to the aforementioned reasons. So far this is the best candidate (picture below) I found in terms of structure (Brazilian-made sigma phoenix fine stone, if anyone is interested), but this is working only from the description of the fine India stone and not an image, which would be helpful to compare to but which I could not find anywhere. This stone seems to be tightly packed, with very few pores, consistent grain and a good ratio of abrasive to binder.

https://imgur.com/a/TLf8Jr4

The idea is to then melt petroleum jelly (solid Vaseline) in a container big enough to submerge the stone so that it bubbles the air out, flipping it when the bubbles stop to make sure none are trapped inside. Ideally this would be done in a vacuum to get all the air out, as I assume it's done in the factory, but the jungle is currently lacking readily available negative-displacement pumps. The melting point of PJ seems to be achievable with a hair dryer (40-70C, depending on the mix), but I could also set up a double boiler if the hair dryer turns out anemic.

So... is this a dumb idea that will definitely not work or actually somewhat sensible? Been reading into sharpening stones for a while, but there seems to be little consensus in a lot of the information. For my applications (mostly sharpening wood working tools) the Norton India with a strop would be ideal, so that's the reasoning here.

Matt.

 

[UncleBoots]

Interesting quest. I once did the Vaseline thing, with an old Norton from the days before they started doing that. I don't remember how I did it; I think I melted the Vaseline in a saucepan, then immersed the stone for a while.

Here is a microscope picture of my (modern) Norton India Fine:

 

[m.wesolowski]

I wasn't expecting to get a microscope image this easily, thank you!

It looks like both have glass bonds, but what kind of seven herbs and spices goes into each is beyond me short of isolating the binder particles chemically and running the material through a spectrometer. Still, it's extremely helpful to have an image. The binder ends up being the only "artistic" factor in the making of cheap stones like these since the porosity and abrasive material is quite stoichiometric, one depending on the ratio and the other depending on the way the stones are produced in the factory. The grit would only matter if there's significant grit variation, but it seems that both are homogenous (I have a chinese AlOx in which the #220 side has some 5mm particles on the surface, it's outrageous).

You mentioned that you used vaseline before on an old norton: how did that go? Over here there's a heated debate of people for and against this, but it seems there's misconceptions from both sides since the debate is on using water on the stones that have been treated and not thin mineral oils. To my understanding, the petroleum jelly when solid would prevent the steel particles from being absorbed into the cavities, but also would prevent the oil from just running through the stone in no time. Water wouldn't create a good interface with the treated stone due to their differing polarities, so the PJ + abrasive powder would just come out of the stone as a tacky muck instead of being dissolved by the mineral oil and put into solution, this thin layer being removed after taping the oil out of the stone after use and leaving a clean surface of binder and abrasive for the next sharpen.

Matt.

 

[UncleBoots]

The Vaseline went fine. I have now remembered that I used a heat gun, pretty much like your hair dryer approach. I have never even briefly considered using water on my India stones, so my only purpose was to make the stone less thirsty for oil. In retrospect, I probably should have tried it without Vaseline first, just for the experience, but I have no issues with the behavior of the stone since it was treated.

 

[nickycat]

Why not just buy and use whatever is in your budget locally rather? Perhaps I don't get what you are aiming to do and why you are set on using an india stone.

 

[m.wesolowski]

Why not just buy and use whatever is in your budget locally rather? Perhaps I don't get what you are aiming to do and why you are set on using an india stone.

Right, I might have been lazy with my explanation.

It's not much of a problem in budget, but rather in the application that I need as well as curiosity.

I want this stone to be used in the workshop, and all the stones sold here make a mess. Waterstones are notorious for getting dirt everywhere, and oil stones that are not prefilled are much the same. Working with wood I don't want the grit and metal dust to get onto the finished surfaces, so that's my reason for wanting a setup without oil or water soaked stones, something that keeps the sharpening media contained and to a minimum.

I usually sharpen with sewing machine oil instead of water since it doesn't dry and helps both lubricate and float the metal particles. The thing about lubricating and using oil is that the film layer, in my experience, helps produce a higher relative grit. Using oil works wonders when sharpening with wet and dry sandpaper, but as soon as you get it on a stone it goes right through to the other side.

Another thing is that most stones sold here have a really poor dishing problem. For wood working tools it's usually better to have a flat stone since chisels and planes are 90% of the time flat edged, and so I want to have a stone as resilient as the norton fine india. That's why I wanted to compare the surface structures as well, as I'm quite certain that both the binder and the vaseline soak aid in giving that flat longevity to the stone, as well as proper use and care for the surface.

I found a stone that seems to have the same properties in terms of structure, but the manufacturer advises the use of water. I'm thinking it's something either cultural or related to the ease of production, but can find few oil stones here, and none of them are pre-filled from the factory.

Matt.

 

[Bill DeShivs]

Just use WD 40 to clean your India stone after use.
Squirt it on and scrub it off with a paper towel.

 

[nickycat]

HI Matt, thanks for explaining your goals with this india stone. I totally understand why you want to avoid water stones and avoid a big mess, I am the same way. I've been using a combination of DMT diamond stones and lapping films. DMT stones require nothing in terms of lubrication. I wipe them with a towel after use and for heavier use, I spray a product called Krud Kutter and wipe clean. I follow the exact process when using lapping films. This effectively contains the grinding debris. For heavy metal removal, I use either adhesive backed 80 grit sand paper attached to a strip of plywood, or my bench grinder (which does release metal dust).

I work with wood too and understand the frustration with the debris. One thing you can do if you have space is create a dedicated "sharpening station", ideally near a sink. Another Idea is to build a simple tray/box which is used to contain all your sharpening supplies and can be moved around and will not leak any liquid if spilled within the tray.

 

[UncleBoots]

Is it possible that the sewing machine oil is thinner than ideal for your application? Seems like a more viscous oil would improve some of what you are talking about.

 

[m.wesolowski]

Is it possible that the sewing machine oil is thinner than ideal for your application? Seems like a more viscous oil would improve some of what you are talking about.

Very likely, yes. That's why use vaseline, which is a paraffin wax + mineral oil mix. It's technically still an oil, but solid at room temperature. If you add a little more oil it liquifies, so I'm assuming that the correct ratio of mineral oil to paraffin wax could be optimized in the petrolatum mix, but that's too much tinkering. This problem is talked about in the patent the Norton company filed for their synthetic abrasive oil stones, and the solution to the seeping of oil is exactly the use of a polar compound within the vitric matrix of the stone, and an example given is PJ. Here's the link to the patent, if anyone is interested.

HI Matt, thanks for explaining your goals with this india stone. I totally understand why you want to avoid water stones and avoid a big mess, I am the same way. I've been using a combination of DMT diamond stones and lapping films. DMT stones require nothing in terms of lubrication. I wipe them with a towel after use and for heavier use, I spray a product called Krud Kutter and wipe clean. I follow the exact process when using lapping films. This effectively contains the grinding debris. For heavy metal removal, I use either adhesive backed 80 grit sand paper attached to a strip of plywood, or my bench grinder (which does release metal dust).

I work with wood too and understand the frustration with the debris. One thing you can do if you have space is create a dedicated "sharpening station", ideally near a sink. Another Idea is to build a simple tray/box which is used to contain all your sharpening supplies and can be moved around and will not leak any liquid if spilled within the tray.

I thought about getting diamond stones, and in terms of hardness they are indeed superb. They'll grind through metal like it's nothing, to that degree they are even better than corundum/SiC. What I was reading about them, however, is that they are too aggressive and the scratch pattern is exactly what you pay for. #1200 will always be #1200, and #400 will always be #400, whereas white AlOx particles have a possibility to achieve ever finer finishes than the actual grit due to its high friability. Even with the advertised grit of Norton fine India being #400, you can achieve superb finishes with the right technique. Looking at scratch pattern alone, some #400 AlOx stones can get up to #800 or even #1000 depending on technique first and foremost, but also the structure of the stone. The ideal structure seems to be a lot of abrasive, little matrix, and few pores, and that's another thing that made me land in the India stones. Again, this is all from reading, to tell for sure I'd have to spend a pretty penny and do some extensive testing under the microscope.

As for the "shame corner of sharpening": I'm working on that at the moment. There's an old router table that no longer has a router laying around, so that might become a good sharpening surface. Moreover, it's right next to the workshop sink, so it's a two for one!

 

[UncleBoots]

FWIW, some waterstones generate minimal slurry: Shapton Glass, Naniwa Hibiki, Suehiro Debado. All of these are dense stones that dish very slowly.

 

[nickycat]

I thought about getting diamond stones, and in terms of hardness they are indeed superb. They'll grind through metal like it's nothing, to that degree they are even better than corundum/SiC. What I was reading about them, however, is that they are too aggressive and the scratch pattern is exactly what you pay for. #1200 will always be #1200, and #400 will always be #400, whereas white AlOx particles have a possibility to achieve ever finer finishes than the actual grit due to its high friability. Even with the advertised grit of Norton fine India being #400, you can achieve superb finishes with the right technique. Looking at scratch pattern alone, some #400 AlOx stones can get up to #800 or even #1000 depending on technique first and foremost, but also the structure of the stone.

Personally I want to spend as little time as possible sharpening my tools, depending on what I am doing and the wood, I sharpen chisels and plane blades 1-5 times a day. With my setup described in my previous post, I can almost sharpen with my eyes closed (not really, but i'm trying to convey its simplicity and predictability). I can easily remove the scratch marks from my diamond stones in maybe 3 minutes max by using progressively finer diamond followed by progressively finer lapping film. The entire process for me is under 5 minutes and as I said, is effortless and I don't need to waste energy thinking about it.

One thing about the grit ratings about diamond stone, you mention

#1200 will always be #1200, and #400 will always be #400

that's not entirely true. Yes, for years you will enjoy the consistent and predictable grit rating of your diamond stones but eventually (after years of regular use) the diamond stones break down somewhat and result in a finer grit.

If you want a sharpening medium which gives such a variable grit, you should look into a coticule stone from belgium. These things are fantastic and I use them for straight razors. You rub a smaller piece (similar to a nagura stone) on the stone with some water to create a slurry. What this does is release very tiny garnet chunks which are embedded in the coticule stone. Garnet is highly friable and as such can be used to vary the effective grit.

 

[m.wesolowski]

Hm... that makes sense. I learned to sharpen directly on the AlOx, but I was looking into some finishing stones. Diamond still strikes me as too rough, but I might get a plate to test the scratch pattern. I was looking into both coticule and ark stones for final hones, setting microbevels, etc. Getting those is quite hard, but I've heard of some stones here that might work the same as coticule, and some similar to an Ark stone.

What I meant with the diamond plates is that they are not friable, and the grit variation is over the years (due to grit shedding) and not in a single session of sharpening. With an India stone you should clean the surface after every use, not only due to steel particles getting in the pores but also due to the finer grit that breaks down. Within one sharpening, you can start with a clean stone with something like #320, and as the grit breaks and you progressively put less pressure it goes to something like #800. Unlikely to be good enough for razors tho, so I finish all edges on the strop with green compound (CrOx, around a JIS 8000 finish). I generally apply light to no pressure on the strop so to minimize the cambering of the edges, as a rule of thumb only enough pressure to make the blade "stick", and that has been good so far. However, I would like to completely migrate to stones and plates, that would (I'd think) prevent me from making some bone-head mistakes and ruining my edges on the leather strop from using too much pressure, which has happened more times than I'd like to admit.

FWIW, some waterstones generate minimal slurry: Shapton Glass, Naniwa Hibiki, Suehiro Debado. All of these are dense stones that dish very slowly.

I'll look into those. If I'm not mistaken the Shapton glass is also a splash-and-go, so that also fits my needs.

Matt.