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I got a new (new to me, appears very old) whetstone today, and was told generally how to use it. I need to sharpen my son's knife, who at 9 years old has much more woodworking (whittling) experience than I.

My question is, because I don't know the history or source of the whetstone in question, can I still clean it the same as I might any others, without detriment to the stone or to the blade?

I am trying to learn as much as I can about sharpening so I don't ruin my son's blade, or worse his experience. I learn from various sources (including https://woodworking.stackexchange.com/a/4144) that I should clean a whetstone so that it can function correctly. With all the many ways I can mess up his blade by sharpening poorly, I want to at least make sure the tool I am using is performing adequately.

I read that some are dry only, others are water only, others are oil only (the stone in question was treated with gun oil to demonstrate prior to me receiving it), and so I am concerned that dish detergent may not be best for all whetstones. On the other hand, I am not clear on what results of suboptimal whetstone cleaning might actually have on the ability of the tool to function properly, or on the knife itself, if any.

Can they all be safely cleaned the same way?

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  • If your stone is natural (which from the description in the Comments below it sounds like) and hard to very hard yes you can safely clean it in any of the methods mentioned in the linked Answer. If in doubt stick to warm soapy water, that won't harm even the softest natural waterstone. – Graphus Feb 27 '18 at 12:56
  • Have you looked up here and/or elsewhere about how to hone a whittling knife properly and how to get it (and judge whether it is) suitably sharp? The standard for whittling knife sharpness is high, they need to be very sharp indeed to work well. You'd have to have been quite lucky to get a single stone that will do all that you need to maintain the cutting edge in tip-top condition, so at minimum I would recommend making or buying a strop. – Graphus Feb 27 '18 at 13:00
  • @Graphus Thank you. It feels smooth to my touch, but I don't know if that is because it is smooth or is 'loaded', or even if smoothness has any relation to hardness. I have looked up and continue to look up sharpen/hone/strop, and hope to understand it soon enough to make a practical effort this week. Judging is difficult, so far a headlamp in a dark room watching for reflections off the blade, and a microscope at 10x looking for scratches, seem to be my best ideas, since I am confident that my technique is poor enough that I wouldn't even get a smooth cut with the sharpest knife. – CWilson Feb 27 '18 at 17:04
  • @Graphus Thank you for the affirmation that a whittling knife must be very sharp, I called a sharpening service who said that whittling knives, especially for beginners, should be intentionally dull for safety, and that sounded... odd? – CWilson Feb 27 '18 at 17:05
  • Re. smoothness and hardness and judging the nature of the stone, the long sides of the stone may be the best place to judge this since they are very likely to be unloaded (perhaps even unused) so the stone will feel, look and act just as if it were newly arrived. Depending on the stone type it could be fairly smooth but still cut reasonably quickly — considered ideal — but as a general thing finer stones cut more slowly due to their finer, smaller-scale, texture. – Graphus Feb 28 '18 at 14:48
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It's worth knowing what the stone is made of, because you can expect different performance from different types, and the use may be different, in particular the appropriate cutting lubricant.

I'm not sure I would use any stone dry, although diamond plates (not stones technically) might be best used dry for some applications.

An old whetstone is probably natural (hard or soft Arkansas), aluminum oxide, or silicon carbide. All these will work well, perhaps best, with a honing oil which is just mineral oil, available from any drugstore (laxatives aisle). That's what the more expensive cans labeled "Honing Oil" will contain.

A waterstone is something different and I won't describe it here except to make the perhaps obvious observation that they are lubricated by water rather than oil. In both cases, the lubricant floats away the cutting swarf so it doesn't load the abrasive surface and diminish the stone's cutting capacity.

An oil stone, whether natural or synthetic, can be cleaned in an ultrasonic cleaner if clean is what you're after. While it will improve the appearance, perhaps greatly, it doesn't by itself address other important conditions such as flatness and fresh, sharp grit on the surface. For that you need lapping.

Lapping is essentially grinding the grinding stone itself. This can be done using a diamond lap like this:

enter image description here

although these are a bit expensive if you're not going to make frequent use of it. There are other alternatives to be found if you search a bit.

Armed with a lapping plate and ultrasonic cleaner, a set of oil stones will literally last a lifetime. I can't say I'd recommend such a setup to most folks, because they wouldn't use it enough to justify its cost. I happen to use stones frequently for various metalworking purposes so it's a worthwhile investment to me and I already have an ultrasonic cleaner for many other purposes.

Even without lapping, a clean stone will likely cut better, and a certain amount of grit renewal can be had by rubbing two bench stones together. Of course you have to have two :)

One last remark, going back to the type, if it's a hard Arkansas stone it is a great stone, probably the most expensive kind out there, but will sharpen frustratingly slowly. That type is more for refining and polishing an edge that's already been sharpened by a coarser stone.

If it's gray, the stone is probably silicon carbide. If it's orange, it probably aluminum oxide. Silicon carbide cuts faster, but wears more quickly so is harder to keep flat. Aluminum oxide is probably the best all-around choice for starters.

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  • Thank you. I am hearing 2 things here: 1) no, they can't all be cleaned the same way (with dish detergent or otherwise), and 2) cleaning properly does make a real difference. For my particular stone, it is just wider and longer than my 5th finger, depth about a third of the width, and a mottled color, about the color of dark pencil lead on the lightest places, and the color of dirty motor oil in others. When I try to use it, the blade (and my fingers) is covered in a dark black grainy muddy chalk. This all led me to believe there is value in cleaning, and hence the question. – CWilson Feb 25 '18 at 14:58
  • Well, I can't speak for water stones, but oil stones can be safely cleaned with dishwashing detergent. That's exactly what I use (Dawn Clear) in the ultrasonic cleaner for that job. Note that the oil is used to keep the stone clean during use, not for periodic overall cleaning. An oil stone is porous and in the best case, is saturated with oil (although it tends to settle out). An ultrasonic detergent bath will remove that oil and the stone will take some time to dry afterward. – scanny Feb 25 '18 at 22:12
  • But once dry, it will again accept oil and you might oil it until it stops soaking in as a last restorative step; that's what I do anyway. Then you just apply a few drops on the surface as you're actually using it to sharpen. Because the stone is mostly saturated, that oil pretty much stays on the surface and floats away the swarf, also making the cutting action smoother. – scanny Feb 25 '18 at 22:13
  • Waterstones (if used with water) will not "load up" as the stone will wear away as it sharpens. oil stones can be cleaned with soap or solvent. If desired "oil stones" do not require oil for use. Light oil, kerosene, even water works well as the purpose is to keep the metal particles in suspension so that they do not load the stone. – Chuck S Feb 26 '18 at 19:42

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