Speaking of tomatoes

[Cliff Stamp]

Awhile ago on the forums someone made a comment that tomatoes were very hard on knife edges, dulling them very fast. It seemed to me at the time it had to be a corrosion issue, but I never had a lot of tomatoes on hand for extended cutting.

This weekend a friend dropped off a couple of dozen and I made a large stew. I was using a Spyderco catcherman and a Dozier K2. At the start both were extremely sharp, catch hair above the skin, and both sailed through the tomatoes efficiently, no slipping.

Midway through the dicing (soft plastic cutting board) the Dozier started to slip on the tomatoes and I finished with the Catcherman which was uneffected by the tomatoes. These steels have a huge difference in corrosion resistance.

The blades were not rinsed during the cutting which lasted for about half an hour because at the same time I was also cooking meat, and frying that and onions and garlic and such.

-Cliff

 

[DaveH]

Cliff, I need a frame of reference, would spyderco's kitchen parer of MBS-26 be as good or better then the catcherman?

Does that mean that a carbon no stainless knife would dull even quicker?

 

[Cliff Stamp]

Yeah it is the same steel. D2 has better light corrosion resistance than 1095 and most tool steels so you would assume they would fare worse in that regard.

Personally it isn't an issue because I rinse and dry blades a lot to prevent foods from melding together as there are times when you don't want the various of independent dishes flavors to mix.

Plus this is kind of artifical because I was cutting with one blade, letting it sit while I cut with another one, if you keep using the same blade rust sets in much slower because it keeps getting burnished off.

I have done chopping trials for example with the Wildlife hatchet while it was raining to see if corrosion had any effect and it didn't as long as I kept working. However if I let the axe sit wet then it would start to spot very quickly.

It is however one of the reasons why I prefer very corrosion resistant stainless steels as gifts for kitchen knives, plus those steels are usually very tough as well.

-Cliff

 

[R.W.Clark]

Just 72hrs ago in response to my statement that tomatos could be used to test

Edge geometry, sharpness, stain resistance and overall geometry.

Cliff argued by saying

they only examine sharpness

Now Cliff is running the very test he claimed tomatos could not be used to do.

Just like he is now saying overall geometry is making the Silver Trident unfit for kitchen use. Guess that does not apply to tomatos though.

What a differance a day or three makes.

 

[Preacher Man]

R.W.Clark,

Could you please post a link to the thread in which these comments were made?

 

[R.W.Clark]

Here ya go.

http://www.bladeforums.com/forums/showthread.php?t=344085

It is about differant testing media.

 

[Cliff Stamp]

Now Cliff is running the very test he claimed tomatos could not be used to do.

This is what I said :

"Cutting tomatoes would not allow any evaluation of geometry as they can't exert any wedging force on a blade, they only examine sharpness. A carrot would show the influence of geometry as it is stiff enough to exert wedging forces on a blade. "

ref :

http://www.bladeforums.com/forums/showpost.php?p=3037156&postcount=34

Note I didn't contend corrosive effects, though cutting tomatoes would not test this either, you would have to let them soak in the juices for an extended period of time while *not* cutting with them.

Just like he is now saying overall geometry is making the Silver Trident unfit for kitchen use. Guess that does not apply to tomatos though.

Right, as I noted, they are to soft to exert a wedging force on the blade. Geometry is however critical as noted for the stiffer vegetables, and other effects like paring which doesn't require a thin blade but a narrow one.

Plus lots of point uses like coring are also geometry dependent. There are lots of other issues, like the upper sharpened edge on the Trident reduce its versatility, the serrations are problematic, and so on.

-Cliff

 

[R.W.Clark]

Uh huh? What part of that "they only examine sharpness" does not apply to my whole statement. If he wanted to argue one point he could have. Instead he tried to discredit my entire statement and now it comes back haunt him a mere three days later.

Looks as if Cliff is having to back peddle a bit.

He also seems to have a problem understanding the differance between edge geometry and overall geometry.

 

[STR]

There is some proof in what Cliff said here that the acid content of certain fruits and veges can and do have an affect on sharpness.

Dishwashers have a more serious affect on high carbon knives also. Stainless is going to have the advantage in many situations where you need to avoid the corrosive nature of acids and detergents combined with water. I have to touch up my high carbon Russell Green River and Ontario knives I use in the kitchen after every dishwashing cycle because I notice a difference in the 'bite' they had versus what they have coming out of a cycle to clean them. When I can catch the wife before hand I prefer to wash these by hand. But she runs them anyway because she always forgets. What I really hate is finding out they have set wet inside there for over 24 hours because the dry cycle didn't quite get them dry all the way.

I don't see this happening in the stainless as much but it does happen. I know that running stainless instruments with an edge through an autoclave/steam sterilizer also has a negative effect on edges. That is primarily why your hygienists have to sharpen their scalers after the autoclave cycle and before they are used to clean teeth. It is also the primary reason most scalpels are made to accomodate sterile disposed of blades rather than ones that need sharpened from dulling in a sterilizer.

Anytime there is a chance for corrosive agents to cause rust on a blade there is a chance of the knife or whatever edged instrument used becoming contaminated with little bacterial spores of Clostridium tetani that love to live in rust, and can be found in dust and dirt as well. If enough of these little buggers become active on a blade and you cut yourself then you have a problem called tetanus or lock jaw to contend with should someone be prone to this infection from never being vaccinated, or not getting their ten year booster. 50 to 100 people still contract tetanus each year in the USA. World wide 3 out of every 10 that contract the disease die from it. Another reason not to use uncared for high carbon blades that look like hell in the kitchen. Stainless is much preferred if you are one that neglects your food prep. cutlery.

 

[crossada]

i really like my kyocera ceramics no fuss

 

[Cliff Stamp]

Instead he tried to discredit my entire statement ...

No, I contended your arguement that you could use it to evaluate blade geometry as I noted in the above. Cutting the foods would be problematic however for corrosion resistance checks, because you have to let them soak, as if you actually keep cutting, you don't get corrosion.

Just like for example cutting wood isn't a good test of corrosion resistance, however letting blades sit uncleaned after cutting fresh woods does examine corrosion resistance as fresh woods contain a lot of water.

He also seems to have a problem understanding the differance between edge geometry and overall geometry.

They both influence cutting ability in the same way, mainly by influence on travel of the blade due to wedging forces, drag as well but to a much smaller extent and which can usually be ignored
[*].

Neither have anything to do with sharpness which is just a condition of edge alignment and grit choice, thus it is medium dependent, sharpness for push cutting and slicing requiring different grit finishes for optimal ratings for example.

...the acid content of certain fruits and veges can and do have an affect on sharpness.

I actually have a hard time accepting this, even after seeing it happen. You are looking at corrosion setting in extremely quickly on the edge to the point that it dulls, with no sign of it on the flats. But I don't see any other conclusion, there is no way it can be a deformation or wear issue because D2 is harder and more wear resistant than the Spyderco stainless.


[*] Main blade geometry also of course controls mass and balance, of which edge geometry is to small an effect in that regard. You don't significantly change the balance of a blade by altering the edge angle from 15/20 degrees, but could if you changed the primary from 5/10 for example.

-Cliff

 

[R.W.Clark]

No, I contended your arguement that you could use it to evaluate blade geometry as I noted in the above. Cutting the foods would be problematic however for corrosion resistance checks, because you have to let them soak, as if you actually keep cutting, you don't get corrosion

I don't see how anyone can deduce that arguement from the statement

"they only examine sharpness"

But keep explaining, it is very enlightening to the reader.

Quote:
He also seems to have a problem understanding the differance between edge geometry and overall geometry.

They both influence cutting ability in the same way, mainly by influence on travel of the blade due to wedging forces, drag as well but to a much smaller extent and which can usually be ignored[*].

Um, No. Overall geometry refers to the knife as a whole not just the blade. It relates to the blade handle relation as well as blade shape. In short the overall design of the knife.

 

[mtngunr]

i really like my kyocera ceramics no fuss

And I really like my discussion threads without people hounding one another from subject to subject, and no fuss....I haven't been here long and this stuff is totally ridiculous already...

 

[howiesatwork]

...
I actually have a hard time accepting this, even after seeing it happen. You are looking at corrosion setting in extremely quickly on the edge to the point that it dulls, with no sign of it on the flats. But I don't see any other conclusion, there is no way it can be a deformation or wear issue because D2 is harder and more wear resistant than the Spyderco stainless.
...-Cliff

Unless polished, the edge "grind" has much more surface area exposed to corrosion, per square area, than a polished flat. That's the reason you see corrosion on the edge first. More places to hold contaminants to set up reactions...
Hope that helps you.

 

[Cliff Stamp]

Unless polished, the edge "grind" has much more surface area exposed to corrosion, per square area, than a polished flat. That's the reason you see corrosion on the edge first.

Very true here as the edges are very rough, when I did salt soaks the edges would run black very quickly, but still in the above it is a very short time. If it had been L6, sure, you can actually see that rust while you are cutting up an apple and eating it. It might be interesting to see it if is enhanced by the finish, for example if the microbevel was set at medium on the Sharpmaker would be be less prone than with a 100 grit AO belt. Which finish would give better slicing edge retention on tomatoes with long partial soaks as in the above.

I don't see how anyone can deduce that arguement from the statement

"they only examine sharpness"

You can't, you actually need to read the rest of the sentance.

Overall geometry refers to the knife as a whole not just the blade. It relates to the blade handle relation as well as blade shape.

If you want to have geometry include the handle design, you can of course evaluate the geometry of the knife by just picking it up so you don't even need to cut the tomato at all. You are free of course to define the terms anyway you want, that isn't common usage though, read the FAQ's for example. Geometry is generally accepted to mean blade geometry, so primary and edge grind, even tip style usually gets a specific label to avoid confusion.

You don't read comments often like "The XXX has geometry issues because the handle texture is too rough." It is strictly true of course, but as noted simply not common convention, if you want to use this viewpoint you could even evaluate the geometry by simply weighing the knife.

Now if you want to make the arguement that you could examine the ergonomics of a knife by using it for cutting tomatoes, well yes to an extent, but in general you want stiffer media for that as well because in very light cutting you don't get a feel for hot spots and such.

Now if you were *carving* tomatoes, making flowerets and such you could examine handle ergonomics because this requires a lot of grip manipulation, but this again is a stretch of the word cutting, which most people would just assume is slicing or chunking them up. Most specific cutting gets its own specific terms.

In general, for pure simple cutting, you get a much better sense of ergonomics and security by cutting harder materials where you have to use more force and/or cutting very slippery materials which lubricate the handle and thus security becomes critical. Still I would not call any of that geometry evaluation for reasons as noted in the above.

If you actually wanted to nit pick the statement I made there is a much more sensible approach. For example really small blades can't cut tomatoes well and thus you could evaluate geometry in that sense because a one inch blade would not be very efficient. I don't think a lot of people would actually think I was contending that when I made the above statement of course, but I think it is a less extracted arguement than "I meant handle ergonomics and security when I said geometry."

-Cliff