Midmark Ritter M7 'Speedclave' sterilizer autoclave, $25.

Autoclaves are used in places like laboratories, dental offices, hospitals, tattoo parlors and wherever else items must be sterilized before use, or for reuse. Some brands of autoclaves sell much better than others, so it would pay you - literally - to familiarize yourself with these expensive little devices!

The autoclave is essentially a high-tech pressure cooker, because it uses high temperature, or superheated, steam at a precisely regulated pressure to do the sterilizing. As you may already know, the boiling point of water varies with atmospheric pressure. At sea level, where the atmospheric pressure is about 14.7 pounds per square inch ( or p.s.i.) the boiling point of water is 212º Fahrenheit (F.) You can turn up the heat under that pot of water on the stove all you want, but it won't get any hotter. All the added heat will only make the water boil more furiously, while staying at 212º.

Way up at 30,000 feet altitude, for example, where the atmospheric pressure is only about 4.3 p.s.i., water boils at only about 150º Fahrenheit! The message here is that if you want to increase water's boiling point, you must increase the atmospheric pressure, and that's just what an autoclave does.

To get the required temperatures needed for sterilization, the autoclave brings the pressure inside the sterilizing chamber to around 15 pounds per square inch, or about twice atmospheric pressure. At this pressure, water boils at 250º F, effectively sterilizing the contents of the autoclave.

The Ritter M7 autoclave is very popular among users of autoclaves, not only because of its handy self-contained water supply, but because it's fast, taking only about 12 minutes to go from cold to full sterilization of the contents.

If you do a little eBay research for autoclaves, you'll notice that for the most part, these units are found in two distinct profiles: the box with the (usually round) opening on the front, and the round aluminum 'pot' style, that looks much like a pressure cooker. As a matter of fact, some autoclaves actually are pressure cookers, because they lack their own heat source and are designed to be used on a stove top, exactly like a pressure cooker! They're more expensive than any pressure cooker you're ever going to find, though!

Finally, I'd like to go into the cleaning of this unit. This autoclave has trays that hold the items to me sterilized. These trays are subjected to cycle after cycle of sterilizing steam, and although the instructions say to use distilled water, few people do, and the chamber and trays accumulate layers of dirt and minerals over time. This dirty film leaves the unit looking brown and grungy, which is not what you want for an item you're posting for sale on eBay. In the last pic above, notice that I cleaned half of one of the trays to give you a 'before and after' look at what a little but of cleaning can do. Which looks better?

To clean off the trays for this autoclave and make it look like it's hardly been used, I use a product that I've used countless times over the years for all kinds of applications, called Sno Bol. Sno Bol, like it's friends Lime Away and CLR, uses the power of hydrochloric acid to remove mineral deposits and rust stains. You can take your pick, but I've had really good results on rust stains with Sno Bol. Whenever you work with any kind of acid, always remember that they really react with metals, especially the softer ones like aluminum, which we're thankfully not working with here. If left on too long, the cleaner will start eating away at the metal itself. And although stainless steel is pretty resistant to these cleaners, extended exposure isn't usually necessary. In the photo below, the entire cleaning process took place in about one minute, leaving the tray looking like new.

One way you can get an idea of how well a machine has been cared for and how much use it's seem is to look in the water tank, by removing the cap on top of the machine. Ideally, everything inside should be immaculately clean, but remember that these things are often left with water standing in them, where they accumulate scale, stains and all kinds of ugly crap. Although Sno Bol can help clean things up for you in such cases, you should still want to check this area before making a purchase.

The sticking point here is - you guessed it - checking the machine to see that it works. The ideal scenario would be for the seller to pour in some water and run the clave through a cycle for you. Unfortunately, though, that's too impractical and you're left taking the seller's word that the thing works as advertised. In cases like these, I strongly suggest that you don't risk too much of your capital unless you're the handyman type. There's not really a whole lot of complicated stuff going on inside this little Rutter Speedclave, and a competent repairman would probably be able to nail down a problem without much hassle.

This unit sold on eBay for $1003.

Photo of Ritter Speedclave M7 autoclave medical sterilizer