What happens to the blade at 473 °F (245 °C)

I'm reposting my question here because I need an authoritative answer and I don't think my original message got read by the craftsmen.

I need to autoclave my razors (because I want to give traditional straight shaves, i.e., not with a disposable blade, in a barber shop). Although wet autoclaves operate at a lower temperature, they are expensive. I can get a cheaper dry-heat autoclave but it operates at 473 °F. Since this is close to tempering temperature I'm concerned that it will damage the blade. Is that true?

PS: The handle will always be steel, like a Wapi.

That is right up there with the temperatures that will soften steel.

It probably depends on the type of steel and the accuracy/precision of the autoclave. I have tempered a few of my razors at ~475-500 deg. F for 2 cycles at 1.5 hours each and the result is still very hard steel (for .9% to 1% carbon steel). So, initially, I'll say it's possible that this will work for you, but repeated tempering cycles may continue to soften the steel (slightly) even if the temperature does not increase.

If the steel is around .5% carbon but has been tempered initially at very low temperatures to retain an adequate amount of hardness, then the autoclave will likely soften it a noticeable amount. But if it's higher carbon, like .7% or more, it may be perfectly fine.

You may have to sacrifice a blade to know for sure. If you have a toaster oven or regular oven with a dedicated (and accurate) thermometer you could run a test to see what happens.

I won't claim to be the final word on the subject, but I can say that I've used those temps and had good results for my steel, others will surely add more detailed info for you. Anyone know the carbon % on a Wapi? :shrug:

Tempering steel will also release and stress in the metal. With the thin ,etal of concave razors and the amount or grinding in the product do not be surprised if the blade comes out warped. You can be sure the metal will move, the question is how much. +1 on what Russel said about the metal type and Amount of carbon. 'Tempering will cause the dissolved alloying elements to precipitate, or in the case of quenched steels, improve impact strength and ductile properties.' - Wilipedia.

Here's more from Wilipedia:
Tempering is a heat treatment technique for metals and alloys. In steels, tempering is done to "toughen" the metal by transforming brittle martensite into bainite or a combination of ferrite and cementite. Precipitation hardening alloys, like many grades of aluminum and superalloys, are tempered to precipitate intermetallic particles which strengthen the metal.
The brittle martensite becomes strong and ductile after it is tempered. Carbon atoms were trapped in the austenite when it was rapidly cooled, typically by oil or water quenching, forming the martensite. The martensite becomes strong after being tempered because when reheated, the microstructure can rearrange and the carbon atoms can diffuse out of the distorted BCT structure. After the carbon diffuses, the result is nearly pure ferrite.
In metallurgy, there is always a tradeoff between ductility and brittleness. This delicate balance highlights many of the subtleties inherent to the tempering process. Precise control of time and temperature during the tempering process are critical to achieve a metal with well balanced mechanical properties.

I don't know if it would meet inspection requirements but a pressure cooker works the same way as an autoclave. You can buy an electric pressure cooker for less than $100.

It's very likely that 473 degrees will ruin the temper on most razors. The tempering range for blades is usually in the 375 to 500 F range, with 400 to 425 being more common. Any time you go over 300 F you should start to worry...

Just my 2 cents,
Josh

I will go with Josh.

Since we don't know the exact steel (but my guest will be 12c27 or similar), we can't really predict the effect on the temper, but this temperature is on the edge from "no effect" to "screw with the temper".

I can't tell you for sure it will totally ruin it, but I can't tell you for sure it won't.

Don't take a chance.




EDIT: If it's 12c27 as I think, it won't do any good to the razor...

http://www.smt.sandvik.com/sandvik/0...ElemFormat=gif

I'm not really familiar with the HRC hardness of razors, but it must be close to knives (57-58)

Vintage razors go from 58 to 62, from what I've been told, so the temper on some would probably be affected at the low end of that range.

Josh

Here's an update for those who are interested:

I wrote to Mastro Livi and he replied that razors subjected to high heat (245 °C) will get softer and softer, losing their edge. I've continued searching and I found a dry heat autoclave that operates at 170 °C for 2 hours. I think this temperature will not be a problem. There is yet another option, which is a pressure cooker at 121 °C for 30 minutes. I think I'm going to go for the dry-heat autoclave because it is smaller and more professional than a pressure cooker, which would be out of place in a barber shop. I also don't want to be in the position of justifying a pressure cooker to the Modena health department. If I purchase 5 or 6 all-steel razors I should be good to go.

Have you looked into getting a UV sterilizing oven? I will be the first to admit that I don't know much about this area, but I have seen some UV devices being used here in the US. They may also be used to sterilize scissors and combs.

Barbers a few decades ago were concerned about safety, too, and they may have had tools that would do the job without ruining their razors.

It's cool to hear that you're looking to offer traditional straight shaves. It's sad that the practice has largely died out.

Josh

Quote:

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Originally Posted by JoshEarl

Have you looked into getting a UV sterilizing oven? I will be the first to admit that I don't know much about this area, but I have seen some UV devices being used here in the US. They may also be used to sterilize scissors and combs.

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I'm not an expert on sterilization, but this might be ok from a material point of view.

BUT

UV have a bad effect on polymers and epoxies, so don't put micarta scales in a UV oven, I'm not sure about the celuloid, but I wouldn't take a chance.

Quote:

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Originally Posted by JoshEarl

Have you looked into getting a UV sterilizing oven? I will be the first to admit that I don't know much about this area, but I have seen some UV devices being used here in the US. They may also be used to sterilize scissors and combs.
Josh

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Hi,

I'm doing some periodical maintenance in Pliva pharmaceutical company (acquired by Barr recently), and they use UV sterilizators in microbiology lab, so I think that this kind of sterilization will be acceptable for barber shop also.
UV sterilization is also used in large air handling units to clean incoming air.

Zoltan

--
"Loza" is another type of rakija, made from grape, and hers main power is to "correct" peoples mind and give super powers to people who drink it.

I believe UV will do an efficient job of disinfecting air and glass because they are transparent. Or a surface in direct “line of sight” with the UV light source, however microbes in the shadows (such as the pivot area on a razor) may live to infect another day.

EDIT:
If I am not mistaken, boiling items in water at 100°C for a minimum of 20 minutes will kill all fungi, protozoa and viruses, and most bacteria.

There are two types of clean. free of dirt and free of microrganisms. To be truly clean all the crud must be removed then your razor must be sanitized. You don't need the full 20 minutes at 100C to sterilze. Check out your local bar, just a few seconds in the sanitizer usually ...Yuuuuck.

A sterilizer might be had on the cheap if you get one second hand from a dentist or such. You might try the auction site at LabX.com Laboratory Equipment New and Used

Quote:

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Originally Posted by CraigJ

There are two types of clean. free of dirt and free of microrganisms. To be truly clean all the crud must be removed then your razor must be sanitized. You don't need the full 20 minutes at 100C to sterilze. Check out your local bar, just a few seconds in the sanitizer usually ...Yuuuuck.

A sterilizer might be had on the cheap if you get one second hand from a dentist or such. You might try the auction site at LabX.com Laboratory Equipment New and Used

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I am sure that you are correct from a scientific point of view but I also have to conform to the regulations issued by the local health department which specify 120° for 20 minutes. I just bought a small, economical steam autoclave from a web site that supplies tatoo parlors. After we cover shaving at the hairdresser school, I'm going to start talking to barbers to find one that will let me work in his shop.

If you are going to be autoclaving your razors, you are going to have problems with rust unless you take appropriate measures. I don't know what will be most convenient for you in Italy or what will meet your inspectors' criteria, but you will need to lubricate the razors prior to autoclaving. I used to use a product called Instrument Milk for my surgical tools. You just soak the instruments in the lubricant to coat them with it prior to autoclaving. It is not greasy and of course is non-toxic. You will find several options if you google "surgical instrument lubricant."

Thank you very much for the heads-up. When I ordered the autoclave, I browsed the list of accessories and also took a bottle of Metrilube from a company called Metrex in Michigan, which does exactly what you say. Since you have experience autoclaving instruments, I have another question. As I mentioned, the autoclave I purchased is relatively inexpensive (ha-ha) and one of the features that it doesn't have is a drying cycle. I'm going to be individually bagging each razor to maintain sterility until use and I was thinking that the packages should really be dried, too. I was thinking about putting them in the oven at a low temperature to dry. Any suggestions?

Yes, that will be fine. When an autoclave exhausts its steam, the subsequent drying cycle is just dry heat so your oven will perfectly replicate that. If your autoclave does not have a drying cycle, it also might not have an automatic exhaust either. That means that when the cycle is complete, you will need to manually exhaust the steam immediately rather than allowing the steam in the pressure chamber to gradually come down in temperature. By doing this, your razors will come out of the autoclave much drier.

Are the bags specifically for autoclaves? They might be an unnecessary expense. An cheaper alternative would be to wrap the razors in aluminum foil. That is adequate to maintain sterility. Alternatively, you wouldn't necessarily need to maintain their sterility at all. Regular razors are not sterile. You are just autoclaving them to kill anything on the razor from the previous customer. Just a thought.

The autoclave does, in fact, have an automatic exhaust of the steam. The problem is that it is really just a glorified pressure cooker. There is a steel chamber with a heating element and temperature probe near the bottom. The bottom is filled with water to cover the element and probe. There is a basket whose bottom actually sits in the water. Then the water is heated and creates steam under pressure but after the steam is exhausted the instruments are still sitting in a little water and are not dry.

The bags are autoclave envelopes with a sterilization indicator spot. I agree with your point that the razors do not need to be sterile for use but rather to kill anything they may have picked up from the previous customer. However, I still need to be able to demonstrate to the health inspector that the razor was, in fact, sterilized. So, my thought is to write the date and the customer's name on the envelope when I open it and then file it. This way there is a paper trail. It would also be helpful in the case that someone wanted to come back later and claim that they caught something from the razor, if they were cut.

Perhaps you can elevate the basket or modify it by attaching a web of wires in it to make a new elevated bottom for the basket. :shrug:
There should be some easy way to keep them out of the residual water. Also, there should be very little water left in there if the autoclave is automatically exhausting.

Is the autoclave shown online anywhere? I'm curious to see it if possible.

Quote:

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Originally Posted by Utopian

Perhaps you can elevate the basket or modify it by attaching a web of wires in it to make a new elevated bottom for the basket. :shrug:
There should be some easy way to keep them out of the residual water. Also, there should be very little water left in there if the autoclave is automatically exhausting.

Is the autoclave shown online anywhere? I'm curious to see it if possible.

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Raising the bottom is an excellent idea and it would be relatively easy to do. Here is the product data sheet (9-liter model, H 100). Unfortunately, I wasn't able to find anything in English.

Here it is in english.

Prestige Medical Classic 2100 Autoclave

He bought the H100 but thanks anyway.

The only other advice I can think of is to be sure to take the bagged razors out of the autoclave and into the oven fairly soon after pressure equilibrates and the autoclave door allows you to open it. By doing so, the residual heat on the razors will help to drive moisture off of the razors and will require less time in the oven. You will want to use some kind of tongs to handle them when hot.

Lastly, be very careful of steam when you open the autoclave. Even after the pressure lock releases, there is always residual steam inside and it can burn you severely. It seems obvious, but I've seen a lot of bad burns on people who forgot about it and passed their arm over the door as they were opening it.

I solved the problem of the razors sitting in the water by dropping one of those steel baskets for steaming vegetables that opens like a flower into the basket of the autoclave. Then I sterilized two Wapis and, when they were done, I released the steam and put them right into a ventilated oven at 60 °C for 15 minutes. They were mostly dry, so I think 20 minutes will do it for sure. The only problem is some discoloration on the handle and blade, which I think might be the lubricant since some of the discoloration rubbed off. In the next tests, I will try wiping the lubricant off better and also do a test without it. Tomorrow morning I'll shave with one of the razors. I don't anticipate any problem because they first razor I sterilized when the autoclave arrived was fine to shave with.

The scales are stainless steel, so if it is discoloured you can be pretty sure it won't be corrosion or something else nasty.

Quote:

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Originally Posted by darrensandford

The scales are stainless steel, so if it is discoloured you can be pretty sure it won't be corrosion or something else nasty.

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Actually, I'm thinking it's soap and almond oil residue (I add extra for a super-lather). Before I sterilize the next razors, I will soak them in detergent and rinse them really well.