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Autoclaving is arguably the best way to sterilize equipment in any lab setting. The combination of heat, steam, and pressure is suited to combat even the most resilient microbes and spores.

However, those very elements that make autoclaves so powerful can also be hard on the articles you’re sterilizing. This is particularly true of precision instruments, certain plastics, or items sensitive to heat or moisture.

But just because certain items are delicate doesn’t necessarily mean they can’t be autoclaved; they may just need special attention. This article will give you tips for sterilizing some of the most common delicate instruments and materials.

Materials To Watch For

It’s good to have a general idea of what may make something more or less prone to breakage within the autoclave. Otherwise, you may find out the hard way that the kind of glass you filled the autoclave with tends to explode when heated.

Some specific articles to keep an eye out for are anything:

  • Made of plastic
  • Heat or moisture-sensitive
  • Metallic

Depending on the exact composition, these may or may not need special treatment or may not be suitable for autoclaving altogether. The first time you autoclave anything in these categories, you’ll need to determine which category it falls into.

Do not autoclave

Certain articles should never be autoclaved, either for safety’s sake or the article’s sake. These include:

  • Combustible items or liquids
  • Electronics
  • Plastics like polyethylene and polystyrene (unless they’re intended for disposal)
  • Devices with optical components
  • Anything glued together
  • Articles with lubricated components
  • Metals like aluminum, carbon steel, galvanized steel, or anything else with a low melting point

And finally, if you aren’t sure about a specific article, contact your manufacturer to ensure it won’t be damaged.

Handle with care

This is a list of delicate articles that require special attention:

  • Soda-lime glass
  • Paper
  • Rubber and silicone items
  • Textiles, especially synthetics like nylon
  • Metals like stainless steel, silver, titanium, or anything chromium-plated
  • Precision tools
  • Pipette tips

While these can all be autoclaved, there are some recommended methods for sterilizing them without risking decreasing their lifespan.

Best Practices for Autoclaving Delicate Articles

Once you’ve established that what you’re autoclaving needs delicate treatment, there are a few best practices to follow when autoclaving.

Prepare accordingly

First, follow the universal best practices for autoclaving, such as removing any residual materials before sterilization.

Next, add a layer of protection by placing delicate articles in a sterile bag that will allow steam to penetrate but still provide a layer of security. Items like pipettes, test tubes, and textiles, especially ones prone to melting, do well in these bags.

Make sure these bags are only filled to 75% capacity. If your articles are too large to fit in these, invest in larger bags to ensure proper sterilization.

While you can use biohazard/bio-waste bags to dispose of plastic Petri dishes, we advise running them in a typical cycle that allows them to melt and combine for easier disposal. Additionally, it is important to ensure all plastics you use in your autoclave are autoclave safe.

Load your autoclave strategically

Many delicate items are made of complex shapes, adding complexity to the autoclave loading process. You’ll want to ensure the articles are distributed evenly, with enough space around them for the steam to circulate freely.

Add extra space around glass items that may expand slightly with the heat to keep them from knocking into each other. This will also add some wiggle room when removing the trays from the autoclave.

You should also ensure that any caps, stoppers, or lids have been loosened or separated from the glass. If they aren’t, the glass articles can build pressure and shatter.

Choose quality water

When autoclaving metal, heat and pressure are only two parts of the equation. Many of the minerals in tap water can negatively affect the lifespan and finish of metal articles.

If you’re using a TOMY autoclave, you can control the exact kind of water in your machine since you manually add the water instead of using a hose or faucet. We recommend using deionized (DI) water with a cup full of tap water to activate the sensor. This will keep your metal articles from tarnishing or corroding.

Adjust the heating and drying times

Delicate items tend to be more sensitive to abrupt temperature changes. This is especially true of glass, which can shatter when subjected to abrupt changes in temperature. The best way to counteract this is to lengthen the periods for heating and drying.

Before removing liquids from the autoclave after the cycle, ensure they’ve reached room temperature naturally.

Metals should be completely dry before they are replaced since moisture can lead to rust or other issues.

What not to do

You may be tempted to reduce the temperature to avoid issues with delicate articles, but this is a dangerous game. As a general rule, proper sterilization requires the temperature to remain at 121°C for around 15 minutes. That’s just a general rule, however, and some items, especially ones in bags, may even require longer periods of sterilization.

Research the exact parameters that the article you’re sterilizing requires, but don’t try to get away with lower temperatures, or you may risk contamination.

Don’t Let Delicate Scare You

Autoclaving delicate articles isn’t rocket science. It just requires you to follow some rules. First, look for anything made of a potentially breakable material. Then, make sure you’ve sorted which materials are delicate, which are good to go, and which shouldn’t be autoclaved at all. After that, it’s only a matter of taking proper precautions with loading and packing and programming a more gradual heating and drying.

If you’re in the market for an autoclave, we can help. TOMY autoclaves are top-of-the-line, offering convenience and ease of use. Contact us today to learn more about our autoclaves.

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