Norton Crystolon is dull

[Barmaley]

I love my JB-8 Norton Crystolon. Unfortunately, it does not cut as it use to be. How I should clean it?

 

[FortyTwoBlades]

Generally cleaning it with a fine bristled brush is enough unless you glazed it, in which case a scuff with a diamond plate or lapping it via the loose grit method generally works well.

 

[The Knife Life]

If your stone is just loaded with metal swarf, I've found that spraying a piece of cardboard with WD-40 then rubbing your dirty stone on the wet cardboard works fantastic for quickly removing all that clogged metal from your stone. Since these are oil stones this method is fine. Obviously don't try it with stones meant exclusively for use with water! (you shouldn't need to though as those are self-refreshing generally)

If your stone is already relatively clean, then it's probably just worn and needs to be dressed/lapped/freshened up.

As FortyTwoBlades said, this can be done easily with some loose silicon carbide powder available at a variety of places. Get something like 80 grit loose powder, sprinkle some on a flat piece of glass, steel, or tile , add a little water, then rub your stone on the mix till it completely refreshes and flattens the surface. You may need to draw a cross hatch pattern on the surface of the stone with a pencil to make sure you've dressed the entire surface when you're done. You shouldn't see any pencil markings if the entire surface has been refreshed. It should cut much better for you then.

 

[Barmaley]

Since I used this stone a lot and I believe it will benefit some flattening I would like to try silicon carbide powder non a glass method. The next challenge for me it is to get right silicon carbide powder. This is what google gave me: https://cuttingedgesupply.store/pro...98083&pr_ref_pid=6610252988515&pr_seq=uniform. It is the right stuff? May I get it locally instead of a mail purchase? Does Lowe's carry it? I visited Tractor Supply and it has black powder as Rock Tumbler Media but I could not find what it was made of. Are silicon carbide powders all the same or there are better grade of it? How much of it should I buy - there are some packages like 5lb but are there any other uses for it besides lapping whetstones? Should I use a respirator, are there any health issues?

Thank you in advance/

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[The Knife Life]

That is the right stuff in the link you provided.

You may be able to get it locally but I can't say for sure. I'm guessing that the rock tumbling media at your local Tractor Supply store is probably silicon carbide powder if it looks black and similar to what's pictured at your linked item. It is used for rock tumbling. Aluminum oxide powder (which is softer than silicon carbide) is usually a whitish or a reddish/tan color although it can be many different colors. Black is usually silicon carbide though. Nevertheless, I have seen some pretty dark looking aluminum oxide, so you can't always go by color I don't imagine.

FortyTwoBlades can correct me if I'm wrong as he is much more an expert here than I as he has developed his own line of sharpening stones so he's seen and knows a lot more.

There may be different grades of silicon carbide powder but you shouldn't have to worry about that at all. You'll be crushing it into finer particles in use anyways so the grading of the size isn't critical. If it says 80 grit, you'll be fine. You can of course use a higher or lower grit as well but that's up to your preferences. Lower grits (60 grit) will work faster whereas a much higher grit (say 320 grit) will work much slower but may be desired if one doesn't want to remove a lot of material quickly, but rather, just condition the surface. The higher grits are really to be used with higher grit stones though. Since this is a coarse stone, the 80 grit will work just fine.

You won't need to buy a large amount of it. 5 lbs is overkill. 1 lb (or even less) will be more than enough as you normally only use a small amount, 1/4 teaspoon maybe to flatten your stone. I haven't really seen many other uses of it in the knife world, so your use will likely just be this.

Here's a good video which demonstrates the entire process and it will give you an idea of how much to use :

You're wise to be asking about the health risks though! You definitely do not want to be breathing silicon carbide dust into your lungs, however, this is a very coarse powder which is far too heavy to be airborne at this size. Besides, you'll be adding water to the little bit you use in the process which will keep any dust down.

If you were using much finer powder, say 2,500 grit, that stuff is much finer and can definitely go airborne so one ought to be careful to not kick up a cloud of dust when pouring or scooping it out and be sure to use water when using it for flattening and conditioning the stone.

A respirator will not be needed at the 80 grit size, especially when using water, so no need to worry there.

Let us know how it worked for you!

 

[Barmaley]

Thank you very much for the informative answer! In the mean time I used WD-40. It made my stone look like new but did not change a bit in its performance. It is still feels like gliding a glass in the middle of the stone but if still feels abrasive at the edges. I wonder what did happened to the surface of it? Did I do something wrong or is it a normal and unavoidable side effect of sharpening? I always used a generous amount of mineral oil which I bought at a pharmacy. Should I do something different? When I just bought the stone it was cutting really fast and not it seems doing its work 10 times slower!

 

[The Knife Life]

You're very welcome.

If you've used the stone a lot, then this is definitely normal as the abrasives will wear down over time. It's unavoidable behavior. Even diamond stones will wear down given enough time.

This is especially true for the center of the stone which typically sees the most use as opposed to the edge which see the least and this is exactly what you're observing.

Using the coarse grit silicon carbide powder will wear away any high spots on the stone which haven't been used much then, as it flattens out, you'll get to this smooth spot on your stone and you'll dress those smoothed out abrasives away revealing fresh, new, sharp abrasives and it will cut much better for you then.

 

[FortyTwoBlades]

It sounds like you've experienced glazing, which is a failure of the stone to shed grit once the surface grains have blunted, causing the stone to burnish instead of cut. This is often the result of insufficient pressure having been used to cause the stone to shed. Oil stones are often quite hard, and intended to be used with hard pressure as a result. The use of oil, being more lubricating than water, is intended to extend the life of the cutting edges of the abrasive to make up for this somewhat, but it does mean that if too light of pressure is used you end up with a glazed stone after a while. Once refreshed, try using it with a little more weight behind your strokes than you did before and it may help prevent it from reoccurring.

 

[Robert Ptacek]

Sorry for hi-jacking this thread but does Barkeepers Friend and a scotchbrite pad do a good job of cleaning discoloration on a stone?

 

[Obsessed with Edges]

Sorry for hi-jacking this thread but does Barkeepers Friend and a scotchbrite pad do a good job of cleaning discoloration on a stone?

To some degree, it can. I'd likely use a stiff brush instead, rather than a Scotch-Brite (they break down with scrubbing and leave a lot of their own debris behind). Bar Keepers works best when it's applied to the surface and allowed to soak for awhile (maybe 15 minutes or longer), as a paste mixed with a little bit of water. Then scrub & rinse.

If the stone is pretty porous, it probably won't clean up completely, as some of the deposited swarf will remain embedded. Even so, the discoloration shouldn't significantly affect the working performance of the stone, so I wouldn't worry too much about that.

Ceramic hones can be cleaned up with a much longer soak in the BKF/water paste. I've cleaned ceramic rods this way, putting them in a Zip-Loc bag with the BKF paste and letting them soak for 3+ DAYS. That was with some Lansky 'Crock Stick' rods that were very heavily loaded with swarf. The soak did almost all the work - basically just rinsed them off afterward.

 

[Robert Ptacek]

To some degree, it can. I'd likely use a stiff brush instead, rather than a Scotch-Brite (they break down with scrubbing and leave a lot of their own debris behind). Bar Keepers works best when it's applied to the surface and allowed to soak for awhile (maybe 15 minutes or longer0, as a paste mixed with a little bit of water. Then scrub & rinse.

If the stone is pretty porous, it probably won't clean up completely, as some of the deposited swarf will remain embedded. Even so, the discoloration shouldn't significantly affect the working performance of the stone, so I wouldn't worry too much about that.

Ceramic hones can be cleaned up with a much longer soak in the BKF/water paste. I've cleaned ceramic rods this way, putting them in a Zip-Loc bag with the BKF paste and letting them soak for 3+ DAYS. That was with some Lansky rods that were very heavily loaded with swarf. The soak did almost all the work - basically just rinsed them off afterward.

Thanks for your tip.I am storing up this tip for future reference.I've worked in a meat packing plant for 20 years and used oilstones for as long at home.I never had a stone clog at home or at work but I see people posting here frequently and began to wonder.

 

[Obsessed with Edges]

Thanks for your tip.I am storing up this tip for future reference.I've worked in a meat packing plant for 20 years and used oilstones for as long at home.I never had a stone clog at home or at work but I see people posting here frequently and began to wonder.

With true oil stones, if they're actually used each time with oil, clogging issues are almost nil. I suspect a lot of the reports of clogging here are often the result of using them dry - they clog very quickly that way and it can happen in a few minutes of heavy grinding. They'll also eventually load up when used with just water, as the water doesn't suspend the metal swarf very well, to be wiped away easily, like oil can do. And if swarf settles a bit, a thin film of oil on the stone's grit also keeps swarf from tenaciously sticking to the grit, which makes them easier to scrub clean when they need it, with something like dish soap & water and a stiff brush.

I've tried them at length with all three methods (dry, watered, oiled) and I'm now firmly convinced of the above.

The few times I've used BKF to clean a clogged stone were after I'd been using the stone either dry, or with water for heavier grinding tasks. I've never needed to do that after using a well-oiled stone - it just doesn't need it.

 

[Barmaley]

It sounds like you've experienced glazing, which is a failure of the stone to shed grit once the surface grains have blunted, causing the stone to burnish instead of cut. This is often the result of insufficient pressure having been used to cause the stone to shed. Oil stones are often quite hard, and intended to be used with hard pressure as a result. The use of oil, being more lubricating than water, is intended to extend the life of the cutting edges of the abrasive to make up for this somewhat, but it does mean that if too light of pressure is used you end up with a glazed stone after a while. Once refreshed, try using it with a little more weight behind your strokes than you did before and it may help prevent it from reoccurring.

This is very interesting! It is true that I used very light pressure believing that this is the best method to preserve the stone. I thought that it is important to save a diamond stone which does not like pressure. My understanding was that Silicon Carbide is very hard but very brittle thus I should not use the pressure not to brake the picks of the abrasive.

Does somebody have a micro picture of the top of a stone after sharpening? I also read that ceramic stones do not get dull which I noted but it is very hard to believe . I got a Sharpal ceramic rod which I love and after 2 years of regular use it does not seems to get dull. I will I get a microscope to see the progress in the sharpening stones.

 

[FortyTwoBlades]

This is very interesting! It is true that I used very light pressure believing that this is the best method to preserve the stone. I thought that it is important to save a diamond stone which does not like pressure. My understanding was that Silicon Carbide is very hard but very brittle thus I should not use the pressure not to brake the picks of the abrasive.

Does somebody have a micro picture of the top of a stone after sharpening? I also read that ceramic stones do not get dull which I noted but it is very hard to believe . I got a Sharpal ceramic rod which I love and after 2 years of regular use it does not seems to get dull. I will I get a microscope to see the progress in the sharpening stones.

Sintered ceramic DOES blunt. The main reason you're probably seeing it continue to use is the burnishing acting like a steel. A lot of companies advertise ceramic hones as never wearing out but by that they mean they never shed grit on their own because the grains have been fused under enormous heat and pressure into a solid shape. Eventually those surface grains DO go dull and you have to recondition the surface to get it cutting again.

 

[Barmaley]

Sintered ceramic DOES blunt. The main reason you're probably seeing it continue to use is the burnishing acting like a steel. A lot of companies advertise ceramic hones as never wearing out but by that they mean they never shed grit on their own because the grains have been fused under enormous heat and pressure into a solid shape. Eventually those surface grains DO go dull and you have to recondition the surface to get it cutting again.

This make sense. I assume that to recondition the surface I need to rub SiC to it? Will it bring it to the factory condition or the baking process at the factory makes the surface better? Should I try to apply light pressure to preserve the stone of sintered ceramic abrasives? Will using water help during sharpening?

I am sure that my rod still is sharp since I can develop burr with it.

 

[FortyTwoBlades]

This make sense. I assume that to recondition the surface I need to rub SiC to it? Will it bring it to the factory condition or the baking process at the factory makes the surface better? Should I try to apply light pressure to preserve the stone of sintered ceramic abrasives? Will using water help during sharpening?

I am sure that my rod still is sharp since I can develop burr with it.

Much will depend on the rod that you have. If it's vitrified bond ceramic like a typical ceramic sharpening stone then that would work fine, though a very fine diamond plate would probably be easier, given its shape. However, if it's a sintered ceramic rod (like a Spyderco ceramic) then you'll NEED diamond, as the difference of hardness between SiC and aluminum oxide is only very slight. The reason why loose SiC works on a Crystolon stone without significantly blunting the abrasive grains on the surface is because the loose grit is acting as a pressure concentrator to break the bond between the grains rather than abrading the grains themselves. If you were to take two hard identical stones and rub them against one another you'd completely glaze the surfaces from the abrasives of equal hardness rubbing against one another.

 

[Robert Ptacek]

With true oil stones, if they're actually used each time with oil, clogging issues are almost nil. I suspect a lot of the reports of clogging here are often the result of using them dry - they clog very quickly that way and it can happen in a few minutes of heavy grinding. They'll also eventually load up when used with just water, as the water doesn't suspend the metal swarf very well, to be wiped away easily, like oil can do. And if swarf settles a bit, a thin film of oil on the stone's grit also keeps swarf from tenaciously sticking to the grit, which makes them easier to scrub clean when they need it, with something like dish soap & water and a stiff brush.

I've tried them at length with all three methods (dry, watered, oiled) and I'm now firmly convinced of the above.

The few times I've used BKF to clean a clogged stone were after I'd been using the stone either dry, or with water for heavier grinding tasks. I've never needed to do that after using a well-oiled stone - it just doesn't need it.

Yes,all this talk about glazing just gave me something else to think about.I even go over my India stone with a magnifying glass to check for clogging after sharpening.I can still clearly see the pores of the stone are still open.I am scrupulous about oiling before and after a sharpening session to float out swarf.Thanks all for input this place is a warehouse of information.A special tip of the hat to Obsessed with Edges for his answers.

 

[Barmaley]

I was trying to envision the process of clogging of SiC stones like JB-8 Norton Crystolon. I assume that the only material which can clog the stone is the metal coming from knives shavings. If this is correct than is should be possible to clean it with Bar Keeper's Friend or similar product. Then it seems that applying light pressure on the stone may prolong its life before resurfacing is needed provided regular cleaning with BKF. Am I wrong here? It is still will be very interesting to learn what happens to a stone top during sharpening: do grains brake away if they chip away making grit change to finer numbers? If we are talking about "glaze" - what actually is it - chipping of grains?

Much will depend on the rod that you have. If it's vitrified bond ceramic like a typical ceramic sharpening stone then that would work fine, though a very fine diamond plate would probably be easier, given its shape.

About the ceramic rods: I did noy get the point of a diamond plate been easier to use. The rod is round and I can not see how a flat plate can help. I thought that I need to get a cloth with SiC grit on it and rub it around it. I assume that for sintered ceramic I would need to get some diamond powder (if such product exist?).

 

[The Knife Life]

About the ceramic rods: I did noy get the point of a diamond plate been easier to use. The rod is round and I can not see how a flat plate can help. I thought that I need to get a cloth with SiC grit on it and rub it around it. I assume that for sintered ceramic I would need to get some diamond powder (if such product exist?).

You can still use a flat diamond plate to refresh the round ceramic rod, just scrub it up and down the length of the ceramic rod and slowly rotate the ceramic every several strokes up and down.

Silicon carbide sandpaper would not be as beneficial here as FortyTwoBlades pointed out. It's not hard enough to do significant refreshing on sintered ceramic abrasives.

Loose diamond powder would be a pain if not impossible, but you can get diamond lapping films and foils readily online.

3M makes an assortment of grit ranges in diamond films (essentially diamond sandpaper) you can find and there are also diamond foils as well which aren't as flexible as the films but still flexible. The films act like regular sandpaper whereas the foils are just that, thick foil, with diamond particles electroplated to them just like a DMT plated diamond stone. They're stiff but they do bend so you could wrap it around the ceramic rod and try it out, but I'd suggest the diamond films first as they're much more flexible.

 

[Barmaley]

It sounds like you've experienced glazing, which is a failure of the stone to shed grit once the surface grains have blunted, causing the stone to burnish instead of cut. This is often the result of insufficient pressure having been used to cause the stone to shed. Oil stones are often quite hard, and intended to be used with hard pressure as a result. The use of oil, being more lubricating than water, is intended to extend the life of the cutting edges of the abrasive to make up for this somewhat, but it does mean that if too light of pressure is used you end up with a glazed stone after a while. Once refreshed, try using it with a little more weight behind your strokes than you did before and it may help prevent it from reoccurring.

Special thanks to FortyTwoBlades for the pressure advice! I started applying serious pressure and the stone kind of improved itself! I got 60/80 SiC grit but I am not sure if I need to lap it since the stone cuts really fast and does not feel like glass but give me a good rasping feeling.