Nonstick coatings on knives

[dcarch]

If you have two glass plates of 5" x 5" together with a drop of water in between, it will take about 350 lbs of force to overcome air pressure. However, according to the law of physics, it will take no force to work perpenicular against another force, therefore to get the glass plates apart, you just slide the glass plates away from each other. Water is a good lubricant. The glass plates act almost the same as suction cups in principle.

As a matter of fact, if you use two optical flat glass plates that are absolutely clean, you don't even need water in between.

dcarch

Air pressure experiement

[rotuts]

your excellent youtube demo does a good job of demonstrating air pressure.

however, two pieces of glass with water (or without water if 'perfectly flat') between then will still be very hard to separate in the vacuum of space.

they are easy to slide with water as a lubricant between them. Cant say how easy they will be to slide without that water, but Id guess it would be much more difficult.

[gfweb]

So there's 350lbs of atmospheric pressure? Doesn't sound right.

[dcarch]

So there's 350lbs of atmospheric pressure? Doesn't sound right.

I rounded it off. Atmospheric pressure (sea level) is 14.696 psi, less if you are on high altitude.

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however, two pieces of glass plates with water (or without water if 'perfectly flat') between then will still be very hard to separate in the vacuum of space.

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That will be a function of water's tensile strength, which I don't know; how much force is required to stretch and break water. The fact is you need no power to separate the glass in vaccum. Water boils and expand very quickly in vacuum.

dcarch

Edited March 28, 2012 by dcarch (log)

[rotuts]

wonder how the 'perfectly smooth' panes with no water would separate in a vacuum.

good point about the vapor pressure of water in a vacuum.

[dcarch]

wonder how the 'perfectly smooth' panes with no water would separate in a vacuum.

good point about the vapor pressure of water in a vacuum.

Haha! you are trying to trick me? :-)

All matter has gravitational force. Therfore the force required to pull two glass plates apart in vaccum depends on their masses.

dcarch

[rotuts]

no 'cohesion', 'adhesion', small force, electrical charge etc?

after all there is the 'sticky-ness' which is what this thead is about?

[gfweb]

The gravitation between two panes of glass has to be trivial compared to the above mentioned factors.

[Toliver]

I'd need to eat a lot of watermelon to want a dedicated watermelon knife.

It so happens we do have a dedicated watermelon knife! We also eat an abnormal amount of watermelon. As watermelon season will soon be upon us, I'll be sure to report on the efficacy of this product.

Is there any reason why they didn't make the serrated edge go along the entire blade length? It stops. That's odd.

[Dexter]

FatGuy,

You don't sharpen the flat side, obviously, but the coating does go all the way down to the beveled edge that is sharpened. When some of that metal is ground away, it grinds off a bit of the PTFE as well, essentially creating a scratched / damaged ridge along the side of the material that sees the most abrasive activity. From there, every slice made peels up a little more of the coating.

[rotuts]

I can't say if this is true by personal experience, but many 'Knife Connoisseur's' here and elsewhere suggest that serrated knives with one side flat and the serrations on only the other side are fine to sharpen.

just keep the flat side flat and only sharpen the serrated side.

"Here It Comes "

'better' serrated knives only put the serrations on one side.

[sparrowgrass]

I bought a set of the Kuhn Rikon knives on Woot. They were very inexpensive--$15 for a set of 4--in lovely red polka dots. They are very sharp, but I don't expect them to last forever. I have NOT noticed any advantage to the non-stick.

[Dakki]

I like Woot. I got a set of Shuns there really cheap.

Anyway, I buy a watermelon maybe twice a year so I might not be the person to ask, but it seems to me that any difficulty cutting it would be wedging on the rind rather than sticking (for whatever reason) in the flesh. Something long, thin, skinny and sharp, like your garden-variety carving knife or a sujihiki would be just the ticket.

[HowardLi]

I can't say if this is true by personal experience, but many 'Knife Connoisseur's' here and elsewhere suggest that serrated knives with one side flat and the serrations on only the other side are fine to sharpen.

just keep the flat side flat and only sharpen the serrated side.

"Here It Comes "

'better' serrated knives only put the serrations on one side.

Better to sharpen the flat side.

[Panaderia Canadiense]

I'll now be able to weigh in about PTFE-coated coloured knives. My supermarket just gave me a red non-stick Santoku (!) for buying $10 worth of shrimp....