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What does cooking have to do with shaving? A lot!

So I have been doing some research into coatings on razor blades and why they are there. Gillette discovered in 1958 (US2937976) that a Silicon Coating on the Blue Blade (Super Blue) yielded a "remarkable reduction in pull." However, they specifically said they did not understand why? They also patented (US3071856) in 1959 the Flurocarbon (PTFE) coating. Again, even with their understanding of the Silicon coating, the PTFE coating yielded yet again a "remarkable increase in shaving effectiveness." However, no explanation as to why!?

After, doing some research, I believe that there is a special "stickiness" that occurs between a whisker hair as it is being cut and the steel. The Keratin protein in the hair and the steel adhere to each other and this is experienced as a pulling at the follicle and discomfort etc. This adhesion occurs at the atomic level (or molecular level) and no amount of blade polishing will reduce the friction. I have yet to understand the chemistry behind these atomic bonds.

To understand this adhesion, I stumbled upon why metal pans are coated with PTFE. My research led me to cooking science. Apparently proteins are highly adhesive to fry pans. Who knew eggs stick - ha ha?! Even highly polished uncoated stainless steel ones stick. The solution to eliminate the "stickiness" is to put a barrier between the metal and the protein. So, if you want to understand why a modern PTFE coated razor blade is better than one of the old crappy Gillette Blue Blades, look to the pans man, look to the pans.

PS: Oh and cooking heat has nothing to do with it either. Cooking science says proteins stick to metal even without heat.
 
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Thank you for this. I always love to acquire a technical understanding of everything and how it works. I actually feel better for having read this. Nice work!

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From Wikipedia - Surface chemistry of cooking: "When meat cooks the proteins on the surface of the meat denature because of the heat. This means that many of the secondary bonds that give the proteins their shape are broken. The protein molecules want to reform those interactions to return to their most thermodynamically stable state. Two opportune locations for the surface proteins to bind are the oil and the surface of the pan. Meat sticking to the bottom of the pan is caused by the interactions between proteins on the surface of the meat binding with the molecules on the surface of the pan. Since the proteins and the surface of the pan, all have a significant polarity, the force of their interactions can be high.


So, my reading of this is that heat does have something to do with it. It denatures the protein causing it to want to bind to the surface of the pan to become thermodynamically stable. All this begs the question - does the cutting of hair break the secondary bonds that give the proteins their shape, thereby ALSO causing an adhesion effect (ie causing the hair to stick to the surface of the blade)?

To be continued...
 
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From Quora - What happens when you cut through matter? "Essentially, a knife is a tool for concentrating force into a very small area, creating a massive amount of pressure on a single line. Every molecular bond has a limit to how much stress it can take. If the force you apply is concentrated on few enough bonds that it exceeds their strength, then those bonds break. Most of the things that you'd cut with a knife are held together by covelant bonds, which connect long chains of organic molecules. When those bonds break, you have unstable molecules hanging off the end, which are very reactive. They will tend to very quickly react with whatever is at hand, including each other. The dangling ends very quickly resolve themselves, so if you remove the knife and put the pieces back together, they have no driving force to rejoin. Chemically, you've forced a single mass to convert into two separate masses."

So, my reading of this is the cut ends ARE VERY REACTIVE and as such will want to bind to the molecules on the surface of the blade - thereby causing the pulling or tugging at the follicle.

To be continued...
 
So why doesn't the sheared hair stick to a PTFE coated blade?

From explain that stuff - Nonstick Pans "PTFE is chemistry's equivalent of an introvert. It likes its own company, but it doesn't like other molecules all that much. Put a load of PTFE molecules together and they clump and stick together like spaghetti. In physics terms, we say there are strong cohesive forces between them. When you see a drop of rain sticking to a pane of glass, hanging in mid-air like a climber on a cliff, what you're seeing is cohesive forces in action. There are strong forces of attraction inside the water tugging its molecules inwards into the shape of a drop. But you're also seeing another kind of force too. There are adhesive forces holding the water molecules to the molecules in the glass. These are called van der Waals forces (pronounced: 'van dur varls') forces, named for the Dutch physicist Johannes Diderik van der Waals (1837–1923) who discovered them (and earned himself a Nobel Prize in the process). On the microscopic scale, van der Waals forces are what cause friction. Imagine a legion of invisibly tiny fingers helping the water molecules cling to the glass. That's what van der Waals forces are like.

In PTFE, the cohesive forces are strong, but there are virtually no adhesive, van der Waals forces between the PTFE polymer molecules and anything that comes into contact with them. Try putting a single drop of water on a nonstick pan. Now turn the pan vertically so the drop has to cling like a climber on a cliff. How long does it stay there? No time at all: it cannot stick to the surface because the weight of the water is many times greater than the frictional, van der Waals forces—so the drop screeches immediately to the bottom of the pan. And notice that it doesn't smear like a raindrop falling down glass. The frictional forces are so low that it stays as a drop as it falls. It's still a drop when it gets to the bottom."

QED
 
Awe... you're just saying that! Well it was to me at least. I couldn't find any good explanation as to why razor blades are coated with Teflon (PTFE) - but now I know! :001_302:
 
Hi,

When thinking on this, remember that heat is always present. Room temperature is very high heat compared to Zero heat. As in Absolute Zero, when all molecular activity comes to a halt. Yes, the reaction of molecules to heat is that they oscillate; buzzing as it were. We tend to think of room temp as No Heat, and above it as Heat and below it as Cold. Molecules think room temp is pretty darned warm. ;)

Oh, and when relative motion is involved there are two resulting forces: Friction and Stick. We engineers actually have a term for everything (of course we do), and when we have both Stick and Friction together in fairly even amounts we call it Stiction.

Stainless Steel will exhibit more Stiction than plain Carbon Steel due to the Chromium present. Silicon, which is really a pure glass, has far less, but the heat required to apply it will anneal the steel, making it easier to deform under load. And, that blade edge is under a lot of load from those whiskers. PTFE requires lower heat to apply, and also greatly reduces Stiction. I always figured that this is why they use it.

As far as using other metals in the alloy, they Cost a lot. They have to be in the entire piece of material, but only need be at the edges. So much greater Cost until someone figures out how to alloy only the working edge. Machine tools are made this way, but a DE or SE blade doesn't really allow for bonding a cutting edge to a carrier like that. This is why Personna gave up on the P74, I think. It was good to woo users of other brands, but then once they had they found profits were too low in the long run.

There is one other steel alloy which makes for a great blade: Cobalt. I have a Straight made from what once was a rather large lathe bit. The problem here is that it must be honed while red hot. That leaves most SR users out. I can see one now, trying to hone on a costly JNat, only to have the razor cut up the stone and not wind up honing the edge at all! :p

Of course, once one gets a cobalt steel SR honed, one really doesn't have to do it again. Whiskers are no match for it.

Stan
 
So, any chemists in the house? Let's advance the state of the art! [10] Why at a molecular and atomic level does the protein [11] in the hair stick to the razor blade?

In the food industry it is a problem called "protein adsorbtion" and the mechanism is not well understood [8]. Also, Gillette understood coating a razor blade will decrease adhesion to the hair but didn't know why or how [9].

Apparently, among other things both heat and high pressure (think cutting force of an edge[0]) will denature protein [1]. This is why the cooking of and cutting of protein are related (also why pans and razor blades are both Teflon coated to reduce sticking.) Proteins are amino acids bound by peptide chains and these are strong bonds [2]. However, the hydrogen bonds in proteins are weak can be disrupted though modest stresses via denaturing [3]. The denaturing of protein exposes carbon atoms in its structure as the hydrogen bonds break. The carbon wants to form a covalent bond with other atoms of a similar electronegativity [4]. The steel of the razor blade has a carbon content to increase its hardness [5]. Because the steel and protein both have unattached carbon atoms these will bond covalently as the electronegativity is identical (2.55); and the iron content is steel is also high which has a close electronegativity (1.83) to carbon. Therefore, the covalent carbon bonds are a contributing factor to why denatured protein "sticks" or adheres to steel (an unsourced conclusion by me.)

However, covalent bonds are normally thought of as bonding two non-metallic atoms [7]. And, the steel is definitely metallic!

Denaturing also involves non-covalent dipole-dipole interaction disruption and induced dipole (Van der Waals) interaction disruption [6]. But, how that relates or contributes to denatured protein's adhesion to steel escapes me at this time.

Anyone take a chemistry class? Mine was 45 years ago - ha!

I have an email into the Royal Society of Chemistry and they are receptive, but I'm not holding my breath.
 
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ouch

Stjynnkii membörd dummpsjterd
He took her in his arms, looked deeply into her eyes and said, "Teflon is a registered trademark of the DuPont Corporation, and as such should only be used to describe its products or services. Please refer to it as polytetrafluoroethylene, or PTFE for short."

Excerpted from Ouch International's Guide to Bad Poetry
 
Hi,

When thinking on this, remember that heat is always present. Room temperature is very high heat compared to Zero heat. As in Absolute Zero, when all molecular activity comes to a halt. Yes, the reaction of molecules to heat is that they oscillate; buzzing as it were. We tend to think of room temp as No Heat, and above it as Heat and below it as Cold. Molecules think room temp is pretty darned warm. ;)

Oh, and when relative motion is involved there are two resulting forces: Friction and Stick. We engineers actually have a term for everything (of course we do), and when we have both Stick and Friction together in fairly even amounts we call it Stiction.

Stainless Steel will exhibit more Stiction than plain Carbon Steel due to the Chromium present. Silicon, which is really a pure glass, has far less, but the heat required to apply it will anneal the steel, making it easier to deform under load. And, that blade edge is under a lot of load from those whiskers. PTFE requires lower heat to apply, and also greatly reduces Stiction. I always figured that this is why they use it.

As far as using other metals in the alloy, they Cost a lot. They have to be in the entire piece of material, but only need be at the edges. So much greater Cost until someone figures out how to alloy only the working edge. Machine tools are made this way, but a DE or SE blade doesn't really allow for bonding a cutting edge to a carrier like that. This is why Personna gave up on the P74, I think. It was good to woo users of other brands, but then once they had they found profits were too low in the long run.

There is one other steel alloy which makes for a great blade: Cobalt. I have a Straight made from what once was a rather large lathe bit. The problem here is that it must be honed while red hot. That leaves most SR users out. I can see one now, trying to hone on a costly JNat, only to have the razor cut up the stone and not wind up honing the edge at all! :p

Of course, once one gets a cobalt steel SR honed, one really doesn't have to do it again. Whiskers are no match for it.

Stan

Hey Stan,

In the food industry I think they are focused on how heat provides energy in the denaturing of protein and the subsequent adhesion of protein to metal. If they were to think about the problem occurring without heat as is the case of high pressure denaturing via cutting force in shaving, it might be productive. This is why I am focusing on the easy to break bonds of hydrogen in the hair protein. How could this contribute to adsorption/adhesion? Maybe this is way to ambitious of a project for a mug like me! In the medical industry they want to solve the problem so stents don't get fouled up. So, the process occurs simply through contact of metal with protein - denaturing does not even need to take place. However, denatured protein certainly accelerates the problem (i.e. cause more adhesion.)

--Glenn
 
He took her in his arms, looked deeply into her eyes and said, "Teflon is a registered trademark of the DuPont Corporation, and as such should only be used to describe its products or services. Please refer to it as polytetrafluoroethylene, or PTFE for short."

Excerpted from Ouch International's Guide to Bad Poetry

Yes certainly Sir.. uh madam.. uh will do! Thank you.
 

Ad Astra

The Instigator
Well. Anyone who has applied black Sharpie to a knife edge while sharpening - to show removed metal, high and low spots - can tell you the Sharpie gets removed.

So. (1) If PTFE is actually on the actual edge, does not the act of cutting abrasively remove it from the very edge where it is needed?

So if PTFE helps ... it probably doesn't survive but a shave or two?

For that matter, (2) does an open comb design actually prevent you from using about 50% of the blade, by covering it? When it's worn, could the half-used blade then be used in a normal razor and be 50% sharp still?

These are troubling matters.


AA
 
Well. Anyone who has applied black Sharpie to a knife edge while sharpening - to show removed metal, high and low spots - can tell you the Sharpie gets removed.

So. (1) If PTFE is actually on the actual edge, does not the act of cutting abrasively remove it from the very edge where it is needed?

So if PTFE helps ... it probably doesn't survive but a shave or two?

For that matter, (2) does an open comb design actually prevent you from using about 50% of the blade, by covering it? When it's worn, could the half-used blade then be used in a normal razor and be 50% sharp still?

These are troubling matters.


AA

"If PTFE is actually on the edge" - Why should you doubt this? Many manufacturers make this claim. Interesting.

"does not the act of cutting remove it" - most certainly. How many tug free shaves can you get from a blade? 3 or 5 or 10. For me after 3 or 4, it drops off considerably. I guess factors like hair genetics and prep time longevity will effect hair abrasiveness and therefore how many shaves you will get before the PTFE is gone.

"open comb head design" - Interesting point. They should definitely NOT have made the combs symmetrical on each side of the head. In that way, your observation could be used for benefit by "flipping" the blade when the 50% was used up on both sides. Catch my drift? Check that! Open comb or Solid bar makes no difference. By your logic a Solid bar would have 0% usage. Right and would last forever? Ha ha Funny guy!
 
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Ad Astra

The Instigator
:a21:

These are the important things in life; to keep one awake at night.

No, I do believe the blade starts out fully coated with the PTFE, but as soon as it shaves, the actual edge loses it.

The "Open Comb Paradox" warrants further study, but I like your line of reasoning.


AA
 
:a21:

These are the important things in life; to keep one awake at night.

No, I do believe the blade starts out fully coated with the PTFE, but as soon as it shaves, the actual edge loses it.

The "Open Comb Paradox" warrants further study, but I like your line of reasoning.


AA

As per US3682795, "It has also been proposed to apply a coating of a corrosion resistant metal such as gold, rhodium or chromium to the sharpened edge of a razor blade by evaporation or sputtering. However, noble metals have not been satisfactory as intermediate layers between the base metal and the polymeric coatings [Read PTFE] as they tend to break away from the shaving edges under the abrasion forces encountered in shaving. Such failure carries away the overlying polymeric shave facilitating coating and this tendency renders such blades commercially unsatisfactory."

But, as of 1969, they knew that the PTFE coated noble metals such as Platinum would break off carrying away the PTFE coating as you suggest.

However, "A more specific object of the present invention is to provide blades with a metal film having improved corrosion resisting properties which is firmly adherent to the blade edge surfaces and provides a sturdy base for polymeric coatings which are formed at elevated temperatures... In general, the above objects are achieved by providing blades having a thin metal film of an alloy of a noble metal (platinum, osmium, iridium, palladium, rhodium, ruthenium or gold) and a strengthening metal selected from the class consisting of chromium, titanium, manganese, niobium, molybdenum, tantalum, and tungsten on their cutting edges."

So, the edge is designed NOT to lose its PTFE coating because of the introduction of a "strengthening metal" such as chromium.

Comments?
 
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Ad Astra

The Instigator
...

But, as of 1969, they knew that the PTFE coated noble metals such as Platinum would break off carrying away the PTFE coating as you suggest.
...
Comments?

Well, 1969 WAS the year of the pinnacle of human achievement - Apollo 11 and "one small step."

Apollo 11 - Wikipedia

Gillette/shaving, too, was its pinnacle razor-wise, though soaps have continued to improve somewhat.

Perhaps the forumite with the electron microscope can chime in, but it seems possible the coating lasts long enough to do some good after all. As with the referenced spacecraft's ablation shield, in disintegration it achieves its designer's goal.

:cool2: It's still unclear, though, if a blade is still 50% good when an open-comb user tosses it.

The solid-bar user will have a brand-new blade after shaving, if the blade does not extend past the bar. Such users are known as "people with beards." :kyle1:


AA
 
:cool2: It's still unclear, though, if a blade is still 50% good when an open-comb user tosses it.

The solid-bar user will have a brand-new blade after shaving, if the blade does not extend past the bar. Such users are known as "people with beards." :kyle1:


AA

Yes, I would say that a blade is still good at least 50% good when an open-comb user tosses it. But, just not as a razor blade. A little trimming and it can be used as a shim. And, a smart fellow such as yourself could think up other uses too I bet. Put enough of them in a small container and you could have a nice paper weight! Among other things...

With a 4 or 5 day growth, the beard might be long enough to actually extend to the unexposed blade giving a young man quite the fashionable look. Maybe you are on to something? A solid bar razor with zero exposure!
 
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