Sharpening on bottom of mug

H

HoB

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May 12, 2004
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Well, on Sunday night I just felt like experimenting a bit and I took a ceramic mug, with a decently fine finish on the ring on which it stands at the bottom of it and proceeded to sharpen two simple Zwillings kitchen knives. To my surprise, they came out shaving sharp :eek: . I thought it would work, just not that well. Who would have though? Definitely the cheapskates way to sharpen a knife.:thumbup:

Btw. I don't take credit for the idea. Sal Glesser meantions this in the Sharpmaker video. I had just never given it a try.
 
I've used this method in a pinch, while on vacation with no other options around. I found that a white ceramic mug bottom works pretty well, you just need to check for imperfections that can catch on the edge before you start.
 
My grandmother use to keep a small crock filled with clean sand to hold her kitchen knives. She'd caredully wash and dry them. Then she'd give them a quick couple of swipes against the top of the crock and plunge into the sand to store. I don't remember her ever sharpening them any other way. They always stayed scarey sharp. :eek:

Sandstone rocks will work too. You can also use your car window to hone your knife in a pinch. Just unwind the window abour half way and use the top edge. I have also occasionally done a sharpening demo using a fluorescent light bulb as a sharpening hone.

Pretty much anything with a fine grit will work, but obviously somethings work better than others. ;)
 
Mugs work pretty well. Any smooth ceramic surface will remove steel. The edge left may or may not be very good, but you can use your coffee cup if you have to... or if you want to impress people at parties.
 
HoB said:
I thought it would work, just not that well.
Click to expand...

I have been using two round ceramic rods to put a fine finish on a knife blade for over 20 years now. From what I have heard, ceramic goes back to Egypt thousands of years ago. They rediscovered it in the last 100 years because it can handle high heat and does not conduct electricity, so it is a good insulator. I think ceramic is different from pottery, in that there is more sand in it.
 
One of my standard sharpening tools for a fine edge are the glass/ceramic rods that are used as filaments in sodium vapor lights.
They always work well for putting on a finish edge.
 
Porcelain like ceramics are made of kaolinite Al2Si2O5(OH)4. After baking they form aluminum silicates aluminum oxide and silica. The Chinese perfected this. Other ceramics ranging from bricks to earthenware are made from various clays, feldspars and quartz. Technically, any inorganic material made via the action of heat is a ceramic, and if mixed with a metal, it is called a cermet-used in electronics, high frequency transformers, ferrite magnets and in military armor (i.e. saturating a cake of boron carbide with molten aluminum would form a rather tough cermet armor plate as listed here http://davidwoolsey.com/asmrb/examples/darpa_armor.html ).

Most of our white pottery ceramics contain aluminum oxide or magnesium oxide (hardness 5.5 or about that of an arkansas stone) so you could consider unglazed porcelain to be a random grit sharpening stone.

Ceramic is such a nebulous term since it applies to hundreds of different things, if not thousands. Almost all abrasives are ceramics... green chrome dioxide, aluminum oxide or ruby stones, silicon carbide, boron nitride, the titanium carbide used to coat the tips of drill bits... all are ceramics. Zirconium dioxide is often mixed with aluminum oxide for grinding wheels that stay cooler and zirconia is used in making ceramic knife blades and crock sticks. Boron nitride has two crystal structures, one resembling graphite and is used as a lubricant, the other is cubic like diamond and is used in place of diamond for grinding iron and steel alloys.

As far as sharpening stones go, ceramic seems to be a blanket term for any stone containing aluminum, zirconium or chromium oxides that don't requre soaking in oil or water... Even Shapton stones are called ceramic, though they are bonded with a plastic substance resembling epoxy.
 
That is just a great idea. Simple and logical. It's one of those tidbits that you say "Why didn't I think of that?" To me, that's the kind of good info that make websites like this so enjoyable to visit. Thank you for passing it along. As long as there is a coffee mug at hunting/fishing camp, I'll be able to touch up a knife.

Good stuff.
 
I just finished sharpening a few of my knives on the bottom of my coffee cup before I hopped onto BF and saw this thread. I can get them to cut paper after my mug sharpening so it can't be horrible. I'll let you know how the edges hold up.
 
do you have to worry about proper angle on the bottom of the mug? or is this just stroking the edge across for honeing?
 
ALWAYS worry about proper angles!

Sharpening knives on the bottom of plates and coffee mugs is an old trick that's been around for years - it's always a hoot to see the looks you get - both when you're sharpening (no one believes it!), and then when they discover how sharp the knife is when they fillet a fish or dress an animal.

I hadn't heard of using the top edge of a car windo before - I'll have to try it! Thanks!
 
When you talk about the bottom of the mug, are you referring to the unglazed ring on the bottom? I'm assuming the glazing wouldn't sharpen very good.
 
I've heard of these two options but never tried them. Very interesting to read about all your experiences. I'm going to have to give it a go.
 
Yes, I was referring to the unglazed ring. It is really not so surprising that it works, the arguments were already given, but that it worked so well, did surprise me. I guess I got somewhat lucky in the cup that I picked as ceramics is not exactly a unified term as Yazuha pointed out. The cup/mug that I picket is a simple $3 model from Bed-Bath and Beyond. One day while doing the dishes, I though that the unglazed portion did feel somewhat similar so something in between the gray and white sharpmaker rods. Of course you still have to worry about the angle. You are using it just like a benchstone. I used maybe 20 light strokes. The angle you can hear. Start with a low angle and increase the angle till the sound changes. Chances are that you are using an angle a little bit too steep, but essentially you are only applying a microbevel.

But bottom line is that it easily shaved armhair and was able to cut figures into paper afterwards. I should mention though that the knives that I sharpened were kitchen knives with a pretty decent geometry and a relatively soft steel, so I didn't have to do much. But for touchups it definitely works. You can clean the mug just like the sharpmaker rods with a scotch brite pad.
 
It is a good idea to remember to clean the steel off the bottom of the mug when you're done, especially if your married (my wife introduced me to coasters long ago) or if you intend to stick it in the microwave to warm up a beverage, the steel acts just like metal...
 
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