Birds of a Feather? Three Knives Together.

Joe,

I appreciate your cogent response to my question.

I would really appreciate Tourist's Expert input on this. I 'll probably be spending a lot of money on good knives for the kitchen but before making a decision on them I need to learn about them.

This talk about angles and steels and polishing edges is very foreign to me and I don't think I'll ever get another opportunity to have an expert tutor me on this subject. This is a terrific place.

Not a problem at all I'll simply step out. Oh and I've spent close to $8K on knives and stones in 3 years for what that is worth.

Joe, I wasn't chasing you out, I just want to take advantage of Tourist's Expertise for all of us.

8K is a lot of money, I don't mind spending it if it's a wise purchase. Spending too little is as bad as spending too much in my eyes. Frugal means spending just what is needed.

You could spend as little as $150 for a couple of knives or as much as I've spent on 40 knives for just one knife. I have way more than I wanted but got interested and started buying knives by different makers in different steels. Needless to say I sharpened them, tested the edges and cutting of each and them I sold most of them. I've also spent a bundle on sharpening stones though I now have found what I consider to be the perfect set for the knives I now own and use.

I didn't think you was trying to chase me out of the tread at all and know that Chico is an expert sharpener however I'm sure I could match him on a knowledge of Japanese kitchen cutlery. As for sharpening all that I can't say since I've never seen Chico's work nor I have no opinion that is based in first hand knowledge but take his word for it. I'm just about getting your questions answer but have no problem if you have a particular person you want those answers from. Really I have no hard feeling at all nor did I take it the wrong way. I'm a pretty easy going guy and don't get my feathers ruffled easily at all.

Rhodemaster said:

I'm becoming rather confused and frustrated, maybe I just forgot how to read.
Okay, I'll try!

I have asked questions that aren't being answered, with each question there seems to be a different aspect of knives being brought into the conversation instead of an answer to the question.

From the reading you've suggested I have come to understand that knives aren't as simple as I thought, but I think the questions I have asked are valid and worthy of answers.

If the goal is to confuse, you're doing a very good job.

Here are the questions that haven't been answered:

Isn't it (the cheap knife you sharpened?) that sharp when I take it out of the package? You cut a strawberry, something I would think any knife should be able to do.

No, it isn't that sharp out of the package. It has what's called a utility edge, not a refined edge. The utility edge will cut, but the refined edge cuts far better and smoother

What's the difference between the knife when you started and what you ended up with? Aside from the edge looking very shiny, what did you accomplish. I recall you saying that it became dull when you cut a zucchini, again something I would think any knife could cut.

The difference is in the sharpness of the polished edge, and how clean of a cut you'll get. The polished, refined edge will last longer than
the utility edge, even on a cheap knife.

Locutus said that the cheap knife would become dull from cutting beef. Why would the knife become dull from cutting beef? What makes the knife get dull so quickly? I thought Beef or any meat for that matter was pretty easy to cut.*

Beef or pork, or etc is striated muscle tissue and is tough.

Tourist said that the edge bends which makes the knife seem dull. So. when I'm cutting meat, the edge is bending? How can that happen? Steel is very hard and meat is very soft, right?

I think that one was covered

JoeC said that European Knives use softer steel than the Japanese Knives. I did some of the reading that you recommended and I'm under the impression that knives are hard or soft because of heat treating. I have more questions about that as well but I'll ask them later because we haven't talked about that yet and I do have a question about the next thing JoeC said.

He said: “ Euro knives are also typically thicker, heavier and require a more obtuse angle on their blade or they will roll over if too thin. “

Is that rolling the same as the bending that Tourist was talking about?

Yes. Heat treating does indeed dertermine the hardness of a knife, but different steels are specifically made for certain "ranges" of hardness, and normally heat treated to that range. see the A.G. Russell steel guide I linked to.

Euro knives are usually specifically designed and heat treated to a lower hardness than Japanese kitchen knives. That makes them much more economical to produce, but much less able to maintain their sharpness for long periods of use. Japanese knives are normally laminated with soft steel on the outside for "toughness" and a hard core for edge retention. Again, this adds to the cost of manufacture. The Euro knife needs to be thicker due to the use of softer steel. (This doesn't make Euro knives "bad" just differently designed.)

If it is and if the Japanese knives have different angles, do they do that to prevent the bending and if so, why wouldn't Tourist have done that to the cheap knife to prevent the problem?

I'll leave that for Tourist.

Tourist has mentioned different angles on razors and on axes, I'm thinking that knives are somewhere in between, but that is a pretty big between. Why are the angles so different between knives. I'll probably ask the same question related to steel if you'll permit me to continue asking questions.

Click to expand...

Okay,I'll go back to black type!

I can't give you the math for this one, but the angle at which a tool, (knife,axe,chisel etc.) is sharpened is determied by the useage and the steel. For example, a short, thick bevel is right for an axe for splitting wood. A longer, thinner bevel is right for a knife.

Now, within the knife world, hunting/camping knives usually have a thicker edge than a butcher knife or a scalpel. The knife designer needs to adjust the design of the bevel, and select the blade shape (geometry) and select the type of steel determined by what the knife is designed to be used for.

(My arthritis in my fingers is kicking in, and I think I'd better quit typing for now! )
I hope I've answered most of your questions!
But by all means, do ask whatever you want to know about this post, or steels or any other topic. If I know the answer I'll post it. If I don't, I'll leave it for someone who does.

Rhodemaster, let me give you a little background into the knives and timing of this post.

First off, Doc, Jim_Slagle and Sattie are trying to build a new, first-rate cooking forum. They're going to need many specialists in that pursuit. JoeC, Locutus and I are the "knife guys." I'm sure the "pots and pans" and "French cookiing" specialists will arrive shortly.

In that mix, some of us have been accused of trying to be gurus, of trying be too lofty in our skills and explanations. So I began this first little competition with the most commonly used knife--the 'chefs' knives or the Japanese gyutos.

But Rhodemaster, we are speaking in generalities here. You are touching upon nuances that are defined by many myriad reasons. For example, one six-inch chefs knives might have better edge retentention than a similar appearing six-inch knife right beside it. In fact, many companies build "knock offs."

If that were the case, we would have to discuss 'heat treatments.'

I chose common chefs knives as our first jumping off point because everyone has one, most people use them daily and recognize them at a glance.

If my little 8-dollar knock-off fails, that's because this entire genre' of these knives does fail--that's the point. The 'failure' is part of the treatise, which is why I want to introduce each knife as a singular individual specimen, and then compare and contrast each one.

Yes, knives are metal and food dulls them. Yes, cutting boards and counter tops roll edges. Yes, a steel should be used to correct every day glitches. No, a steel is not a sharpening device.

Yes, I sharpen cheap knives for clients. I want them to get the most out of their investments. But you have to give us a chance. I can name two dozen steel alloys just sitting here--and those are just the "super steels."

If you let us untangle the maze of knife attributes, you find find answers, but more to the point, you will find clarity.

Tourist...

I think we're coming from the same place, just that you have a big head start on me and I think on a lot of other people reading this.

“some of us have been accused of trying to be gurus, of trying be too lofty in our skills and explanations.”

I'm beginning to believe that there may be some truth to that as I think my questions are basic questions that would enhance my understanding of knives in the kitchen.

“But Rhodemaster, we are speaking in generalities here. You are touching upon nuances that are defined by many myriad reasons. “

I think my questions are very general in nature, just slightly behind the rest of you in the learning curve.

So I'm going to ask the questions again, maybe by rephrasing them you'll understand the question so you can answer them. I did the reading you referred to so I think I may have a better base on which to ask questions.

Here's the first question.

The knife you started with according to Locutus has something called a “utility edge”, he also refers to a “refined edge.” I'm assuming that what you do when you're sharpening a customer's knife is 'refining the edge, ” is that correct?

Assuming that is the case, I can understand how the polished edge is going to cut more cleanly. Where you lose me is in how the knife can became dull so quickly.

The questions I asked were:

“Locutus said that the cheap knife would become dull from cutting beef. Why would the knife become dull from cutting beef?

What makes the knife get dull so quickly?

Tourist said that the edge bends which makes the knife seem dull. So. when I'm cutting meat, the edge is bending? How can that happen? Steel is very hard and meat is very soft, right?”

These questions are VERY much general questions about how and why knives dull. I think this is a component part of the “maze of knife attributes” as you called it.

I am trying to focus on this ONE PART of the “maze,” before moving on to other parts so I can understand when you are sharing your expertise. I believe clarity comes from focus.

Rhodemaster, be patient. You will get the info you need.

But I believe we should approach this more as a tutorial. This is now akin to teaching someone how to drive, and before the car is even moving or the parking brake released, the student wants info on ABS.

In a nutshell, knives dull quickly because the alloy is "soft" due to its heat treatment, or the composition of the steel does not contain the more superior (read: 'expensive') elements of things like vanadium, molybendum or manganese, or the cutler deliberately buys this steel to avoid wear to his stamping machines.

Softer steels wear quicker, and have poor edge retention--and bend easier from handling. And banging them on a poor cutting board, clanging them together in a sink or drawer and dishwashing them will bend them. (A dishwasher has a revolving jet spray which bounces the contents.)

As for the "polish" of an edge, that's an entire debate on its own. Some people simply prefer a rougher or more "toothy" edge. They like the way it 'grabs' when cutting. Some people prefer a mirror edge. Some alloys do not receive a benefit in a mirror finish, not can they keep it. Some alloys perform better and better as the edge attains increasing levels of refinement.

But as I stated, the reason for beginning with a cheap knife was to actually apply these techniques. Consider them a "before" picture in a weight-loss ad. That knock-off had all of the poor attributes of a failure waiting to happen. It had little, if any additional elements other than chromium, which makes it "stainless." The blade blank was stamped. To be 'stamped,' it needed to be soft. And when sharpened, it could not hold an edge.

In other words, I demonstrated a baseline, simply that.

If you haven't yet, please watch SEE THE VIDEO at:

http://www.altonbrown.com/shun/shun_edge.html

Tourist...

I'm asking for clarification on things you have already said, you cannot build a house on an unstable foundation and moving on with less than a basic understanding of what we have covered seems to be leaving out essential blocks of knowledge.

I think learning about alloying steel at this point would be, as you so correctly put it, discussing the functional aspects of ABS when we're talking about learning to drive. That would definitely confuse the issue. I also think discussing “toothy” and mirror edges are a bit beyond the point of this discussion as well and so I'll try not to become sidetracked with such discussions.

As I understand what you said, knives dull quickly because they are of a softer material.

You've also explained that the edge will bend or roll from improper handling and “banging them on a poor cutting board.”

Here's a point where I am again becoming confused by the information here.

JoeC said that European Knives use softer steel than the Japanese Knives; he also said “ Euro knives are also typically thicker, heavier and require a more obtuse angle on their blade or they will roll over if too thin. “

SO.... European knives are made of steel that will dull more quickly but are designed so that they can better withstand mishandling. Do I have this correct?

You still haven't answered the question I asked about what makes the knife go dull?

Locutus said that a cheap knife will become dull from cutting meat and I assumed (incorrectly?) that the edge was somehow bending but now you're telling me that the edge is bending because if improper handling.

You talked about how the cheap knife went dull after your wife cut zucchini with it. You said:

“The tip and the edge about an inch back still seemed crisp. The portion from the ricasso forward about two inches felt the same. However, that "middle area" already had the sensation of being worn. There were a few pieces of zuchini in the sink, and made some slices.

Yes, the knife still sliced. The rear portion of the blade did so quite easily. But those strokes had a familiar "drag" feeling I've come to know as a degradation of the edge. “

Maybe I'm not asking the question correctly. I'll try to use your expert terminology to make the question more clear in hope of receiving an answer.

What caused “ he sensation of being worn,” and “a familiar "drag" feeling I've come to know as a degradation of the edge”?

What adds to this confusion is your talk of angles on knives.

Are the angles only there to prevent the edge from bending when the knife is mishandled or misused? If I were very careful to only use and store my knives properly, couldn't I use the same angle as on a razor blade on my knives?

Rhodemaster said:

JoeC said that European Knives use softer steel than the Japanese Knives; he also said “ Euro knives are also typically thicker, heavier and require a more obtuse angle on their blade or they will roll over if too thin. “

SO.... European knives are made of steel that will dull more quickly but are designed so that they can better withstand mishandling. Do I have this correct?

Click to expand...

That is basically what I meant, they won't stay sharp as long as a harder steel knife will nor can them take the acute angles when sharpening as the harder knife. The harder knife is easier to chip while the heavier Euro knives edges will roll. It is a toss up between the two as both have their advantages and disadvantages it really depends on what you want to cut.

Rhodemaster,

What is your "screen name" on KnifeForums?

Rhodemaster said:

Tourist...SO.... European knives are made of steel that will dull more quickly but are designed so that they can better withstand mishandling. Do I have this correct?

Click to expand...

Yes, that's the answer--for that segment of the debate. I wish you would view the Alton Brown video.

Locutus said:

Rhodemaster,

What is your "screen name" on KnifeForums?

Click to expand...

What? I don't understand your question.

Rhodemaster said:

What? I don't understand your question.

Click to expand...

Simple. People have many different names or handles depending on the forum. I've had four different names over the years. In fact, I have several different names in real life.--Chico

Never mind.

Why would I have a different name on Knifeforums? Is that supposed to be a joke, I don't get it.

Tourist...

Alton Brown's video is very entertaining but I need more clarification.

Alton “dulled” his knife by using an electric knife on a piece of foam, that was entertaining but I'm asking you to share some of your expertise in explaining how a knife becomes dull when cutting beef and zucchini.

He also showed the different angles on the edge but really didn't explain why each angle is selected.

I'm actually more confused than enlightened at this point.

Alton Brown's video is a promotion for his Shun Knives and he does a very good job of explaining why I should buy his knives but that's not answering my questions.

Can you answer them for me?

Rhodemaster, it is quite obvious, to me at least, that from your excellent command of the English language used in your posts that you are not having any trouble understanding the very simple, and straightforward answers to your questions.

I am happy to answer anyone's questions to the best of my limited ability, but when I am dealing with an obviously educated person, who feigns failure to comprehend the very language which he uses so well, I won't play anymore.

Locutus,

Frankly, I do understand English both the written and unwritten words.

I don't know what I did to cause you to want to start a fight with me but I will assure you that it was not my goal.

I came across this thread with Tourist talking about knives. He seems like an expert and I'm seeking knowledge. There is no one better to ask questions of than an expert in that field.

I continue to ask the same question because the question isn't being answered.

I don't understand why it's so difficult for me to receive a simple and straightforward answer to a question.

This would be simple to resolve, how about we let Tourist share his expertise by answering these questions. He is a professional in the industry so he must have the knowledge.

These are the questions I'm still asking, I would appreciate, as Locutus put it, simple straight forward answers to them. I'll simplify the questions and make them as general as possible so we're not becoming overly specific.

First:

How does a knife become dull cutting things such as meat and soft vegetables (like zuchinni)?

Second:

JoeC finally explained the purpose behind different angles on edges. They are chosen for the task the knife is made for. That makes sense. What is confusing is the references to hard and soft steel and how that relates to angles. So here's the question:

Why wouldn't you have chosen a more obtuse angle for the knife used to cut zucchini and more specifically, how is the angle chosen?

And last:

How does the angle on an edge effect the ability to remain sharp? This is assuming that dull is different from bent.

I hope the frustration I'm sensing in Locutus' post isn't going to prevent me from receiving the answers to these questions. An expert should be able to explain the basics of his field to a layman, after all he was once a layman as well

Rhodemaster said:

First:

How does a knife become dull cutting things such as meat and soft vegetables (like zuchinni)?

Second:

JoeC finally explained the purpose behind different angles on edges. They are chosen for the task the knife is made for. That makes sense. What is confusing is the references to hard and soft steel and how that relates to angles. So here's the question:

Why wouldn't you have chosen a more obtuse angle for the knife used to cut zucchini and more specifically, how is the angle chosen?

And last:

How does the angle on an edge effect the ability to remain sharp? This is assuming that dull is different from bent.

Click to expand...

I will give it a try if you are OK with it other wise I will let Chico answer for himself if you prefer.

First all knives get dull regardless of what you cut with them. Every thing you will cut be it plastic rap on a package of meat or the meat inside will dull the edge a bit every time you use the knife. A knife over time will become dull even if not used just sitting in a block now that will take a lot of time but normal oxidation will cause that. There is no such thing as a blade that will stay sharp forever but if you find one I will be the second person in line to buy one.

Now as for meat and vegetables in particular in regards to this question, both have grit in some form or other in the case of a vegetable, microscopic particles of grit such as sand or acids in the cells themselves. Acids even mild ones will degrade an edge over time. An onion for example contains sulfuric acids that will degrade any steel over time. Meats also contain small amounts of corrosives elements such as alkaline, acids etc that can corrode an edge. Now with that said some steels sold in kitchen knives are not suited for the task period regardless of how shinny and neat they look.

A steels hardness are based on a scale which there are several of them by the way. The Rockwell scale is most used in regards to cutting tools. A Wusthof chef's knife will be about HRC 56 on that scale while a Hattori HD will be HRC 61. Now this scale without too much detail by itself doesn't mean much but there are big differences in hardness between HRC 56 and 57 as it is a scale on a curve. Man do I hope I didn't confuse you there but that is what is meant by soft steel and hard steels.

The harder the steel the thinner a blade can be made and the more acute the edge can be sharpened. Again there are trade offs for it all with advantages and disadvantages. Harder means more brittle while softer means easier to bend. A good example is a sword. You can't make one out of most kitchen cutlery steels as it would shatter. Swords as axes are softer steel than any functional knife but they are capable of remove limbs with little effort and not real obtuse edges.

So to sum this up the steel, level of hardness, knife geometry in relation to what the job at hand is will dictate the edge required to do the job. In a kitchen it really isn't that big a deal other than a good quality sharp knife will slice food and a poorly designed knife will not.

Joe, thanks for the response, that's why I didn't want to chase you out of the conversation.

The answers are pretty clear at this point with one fine point that came up from your answers.

I'd like Tourist to explain this to me....

Does the angle have anything to do with the knife staying sharp? I know it helps keep the edge from bending, but what about staying sharp?

and I guess I lied because there is another one.

How did you decide on the angle you sharpened the knife in question at? Could it be that a different angle would allow the "cheap" knife to perform better?

Alton Brown tried to simulate two edge conditions.

The first was a simple bend from rougher handling. The edge was still there, and it could be coaxed back into place.

The purpose of trimming the giant foam knife was to simulate a knife with no edge. It's a condition that happens over time. In fact, you can find it yourself. If you have a knife that is dull, find a lamp with a strong beam, like one of those reading lamps. Turn the knife upwards so the edge is pointed directly to you, and you will find light reflected up to you on the edge.

In other words, there's a flat spot. On a sharp knife, you will see no light. I use this technique to check the edge as I sharpen. I have a 'soft hand' in the jargon of the tinkers. I only remove the least amount of metal I can during a repair.

He compared and contrasted two distinct types of conditions on why a knife doesn't cut as it would in a pristine condition.

As for hardness, a higher Rockwell rating is a singular component of overall edge retention. There are several factors--that's why Alton Brown explained the numerous elements added to an alloy. If you have a brittle alloy--but a higher Rc, the knife can chip its edge.

Most of the knife guys here use a knife to slice. When you're slicing you are using a more tender touch, as opposed to chopping. A cleaver does have a more obtuse angle.

This is why most gyutos (chefs knives) are sharpened at a wider angle than a nakiri, which is used just for vegetables.

And compromises are a necessary problem. There is a Japanese knife called a "santuko." I've heard it really means 'three men in a boat,' but the important thing is that 'san' is Japanese for three. The santuko does three things.

The first third near the tip slices, the mid part is a like a gyuto, and the back third is for "heel chopping." (The tip is pressed into the board, and the knife chops by raising and lowering the rear of the blade.)

Three distinct jobs with one edge. I try to keep that kind of a knife around 12 to 15 degrees--and I admit I have some jackknives that a finer edge. But most real-deal Japanese santukos are at about Rc 62, and lead trouble free lives.

And a good cutting board is part of this equation.

Rhodemaster said:

Joe, thanks for the response, that's why I didn't want to chase you out of the conversation.

The answers are pretty clear at this point with one fine point that came up from your answers.

I'd like Tourist to explain this to me....

Does the angle have anything to do with the knife staying sharp? I know it helps keep the edge from bending, but what about staying sharp?

and I guess I lied because there is another one.

How did you decide on the angle you sharpened the knife in question at? Could it be that a different angle would allow the "cheap" knife to perform better?

Click to expand...

I'll leave the first part to Chico about the edge angle and staying sharp.

Now here is how I decide the angle to sharpen at. I follow what the manufacture put on the knife to start and keep that for awhile. As I get used to the steel in the blade, its profile etc when it comes time to thin it I will then experiment with the edge angle a bit usually by making it a bit more acute or leaving it at the angle I thinned at. You can tell when a knife needs thinning when what it used to fall through starts to bind a bit or you apply more pressure to get through it. Now if it chips or rolls it needs a more obtuse angle at which point simply change it a bit if it doesn't cut better than it did when first received I give it a more acute edge.

Now over time I've learned the knives I own and what it takes to keep them in laser sharp shape. One other note as every knife I get regardless of who makes it I sharpen it before using it. Now I don't take it to my course stones but do start about about a 1K grit and work up. Most knife makers rarely sharpen a new knife higher than about 700x grit with few exceptions. I like my kitchen knives taken for the most part a lot higher and will get into the reasons at your request just don't want to add more to this tread that hasn't been asked yet though I'm sure you will eventually.

I'm beginnng to think that perhaps we should have started with santukos.

"Rachael Ray vs The Tourist."

Moderator: When does a German made knife constructed of Chinese steel become Japanese?

Moderator: Chico, we'll have you begin. When does this knife become Japanese...

The Tourist: When you have your own TV show...

Tourist,

Thanks for the response.... I'm beginning to “get it.” I may not be the fastest student in the class, but I certainly show up every day and pay attention.

Between Joe and you, I think I understand that the edge “wears” over time from corrosion and such. A while back Locutus said that cutting up 3 or 4 pounds of meat would dull a knife. The acids in beef are that strong as to eat away steel in that short a time?

Maybe I'll become a vegetarian, except that the zucchini your wife cut up must have been even more acidic because it only took one of them to dull the knife. Can you live on water alone?

Now I know that you're an expert at sharpening kitchen knives so this may be outside your realm but I'll ask anyway.

What about cutting paper? I don't think there are acids in paper that will eat the steel, so how does cutting paper make a knife dull?

Thanks for being understanding, I really want to come to understand this

Rhodemaster said:

Tourist,

Thanks for the response.... I'm beginning to “get it.” I may not be the fastest student in the class, but I certainly show up every day and pay attention.

Between Joe and you, I think I understand that the edge “wears” over time from corrosion and such. A while back Locutus said that cutting up 3 or 4 pounds of meat would dull a knife. The acids in beef are that strong as to eat away steel in that short a time?

Maybe I'll become a vegetarian, except that the zucchini your wife cut up must have been even more acidic because it only took one of them to dull the knife. Can you live on water alone?

Now I know that you're an expert at sharpening kitchen knives so this may be outside your realm but I'll ask anyway.

What about cutting paper? I don't think there are acids in paper that will eat the steel, so how does cutting paper make a knife dull?

Thanks for being understanding, I really want to come to understand this

Click to expand...

I wouldn't worry much about the acids and alkaline in the food we eat for the most part unless your stomach is steel lined. Sorry I just couldn't resist that come back. You want to have some fun take a piece of raw liver and drop it into a glass of coke and watch it dissolve.

Rhodemaster said:

Tourist, The acids in beef are that strong as to eat away steel in that short a time?

Click to expand...

When we say "wear," we mean by abrasion, not by acid. And yes, a metal knife can wear itself dull within one job. In fact, I know of a great many hunters who hold a sharpening stone in their left hand as they field dress or bone a deer with a knife in their right hand.

Now I know that you're an expert at sharpening kitchen knives

Click to expand...

At the very least! Actually I am a zen guru in the disciplines of romance, V-twin engines from 1936 forward, 100% blue agave tequila, ethnic familial negotitions with anyone other than my Aunt Clara, and the fine art of absconding with any ruminat sheep belonging to hobbyist forum moderators.

What about cutting paper?

Click to expand...

Paper in America usually has fine white powder (made from stone) impregnated into the construction to enhance the snow white color. Cutting paper is tantamount to rubbing the edge of a knife on a rock. Cardboard can actually be worse.

Now we're talking about abrasion dulling a knife instead of acids...

That raises a question.

You said:

"The purpose of trimming the giant foam knife was to simulate a knife with no edge. It's a condition that happens over time. In fact, you can find it yourself. If you have a knife that is dull, find a lamp with a strong beam, like one of those reading lamps. Turn the knife upwards so the edge is pointed directly to you, and you will find light reflected up to you on the edge.

In other words, there's a flat spot. On a sharp knife, you will see no light."

So a dull knife is flat on the edge, caused by abrasion.

Since the edge is formed by the intersection of the two angles you talk about, why would the edge change to flat?

Mountains don't become plateaus over time, they become more gentle mountains.

I'm also confused about the abrasiveness of meat. How can meat be so abrasive that it dulls knives to the degree you mention?

"In fact, I know of a great many hunters who hold a sharpening stone in their left hand as they field dress or bone a deer with a knife in their right hand."

I would think that something that abrasive wouldn't feel as smooth to the touch. Is that for real? Why don't they make hunting knives out of something stronger?

Actually, it's amazing that knife edges don't wear away faster. Obviously, they are very thin--minor fractions of an inch thick. In the case of black obsidian knives I've heard that the edge is actually only "molecules wide."

The edge is a wedge. The area directly behind the edge is wider, and then wider still as edge wears. This wider area is what reflects light. It is quite blunt and flat, and easily reflects light. And yes, it wears by cutting food, even "softer" foods like beef.

(Take a knife of your own, examine it in the light. Out of box it was sharp, now it reflects light. Your own knife has "worn away" while in your own hand, and you only cut soft things.)

Yes, a knife can go dead flat within a day. That's a combination of poor quality soft steel and handling. But a good knife, properly sharpened with good care can go several months. In the case of Mr. Brown's collection, with many knives he spreads out the work load.

For him, a year can be a correct period of time.

BTW, the real answer here is never to let a knife go dead flat. I'm always checking my personal knives. Caught in time, a knife with any form of degradation can be "brought back" with steels or strops.

If a knife is pushed beyond a prudent condition, you have to remove metal with a stone.

"The area directly behind the edge is wider, and then wider still as edge wears."

The area behind the edge being the angles we were talking about?