Let’s be honest, we all have been unsure about autoclavable materials at some stage, and wondered “Can I autoclave this?”
Autoclaving ensures our lab equipment, media, and other articles are contamination-free.
However, not everything is autoclave-safe.
Some materials cannot take the high temperature and pressure conditions of autoclaving, thus it is important to have a thorough knowledge of autoclave-safe materials and avoid the mistake of putting the wrong article under the heat.
In this article, we will break down the different lab items that are autoclave-safe and those that aren’t, and explain why some items should never be placed in the autoclave.
Why Autoclave Over Other Sterilization Techniques?
Most of us know how autoclaves (Figure 1) work. Saturated steam under high pressure, typically from 121°C to 134°C, does the sterilizing.
This combination of pressure and high heat allows the killing of microorganisms like bacteria, viruses, fungi, and even the very pliant spores. It is more effective than dry heat, allowing it to kill microbes more efficiently.

It also has the advantage of being able to sterilize both solids and liquids and funny-shaped lab objects.
For a deeper comparison of lab sterilization techniques, check out our other guide.
Workflows That Use Autoclaves
Some of the most common workflows in the lab that require autoclaving include:
- Media preparation for microorganisms, cell culture, and plant tissue culture;
- Preparation of sterile solutions to be used in a variety of molecular biology techniques;
- Sterilization of tools and equipment like pipette tips, to be used in experiments;
- Sterilization of lab waste before disposal.
However, not every material and container is compatible with autoclaving.
Some materials can lose their viability, structural integrity, and shape, and may degrade under autoclave conditions. So, what materials can be autoclaved?
What Can Go in the Autoclave?
The following materials can safely go in the autoclave and can even be re-autoclaved:
- Plasticware: Polypropylene (PP) or Polypropylene copolymers are safe to be repeatedly autoclaved. They can withstand the heat.
Generally, pipette tips, bottles, beakers, centrifuge tubes (MCTs), and Buchner flasks are safe to be autoclaved.
Pro tip: Always check for the label ‘Autoclavable’ or material quality to be Polypropylene to ensure the plasticware is autoclave safe. - Glassware: Borosilicate glassware is completely safe to be autoclaved as it can withstand heat shock.
Test tubes, beakers, conical flasks, glass pipettes, and petriplates are a few examples of glassware that can be autoclaved.
Pro tip: Check for the Borosilicate label before putting glassware in the autoclave. - Metal Instruments: Stainless steel and heat-resistant alloys are autoclave-safe.
Surgical tools, forceps, spatulas, and scalpels are commonly sterilized by autoclaving. - Media: Most types of culture media can be autoclaved in plastic or borosilicate glassware. However, precautions must be taken to ensure the components that are not autoclavable are sterilized separately.
Let’s expand on which types of media and broths are safe under the heat.
Autoclaving Media: Which Types are Safe Under the Heat
Most culture media that are commonly used in the lab require an initial sterilization step in the autoclave, to ensure they are contamination-free.
- Liquid broth culture media like LB are safe to autoclave;
- Solid culture media containing agar are autoclaved first and poured into petriplates;
- Plant tissue culture media are autoclaved before use;
- Cell culture media are also autoclaved first to ensure the media is free of microbes.
The most common media and solutions include:
- Nutrient broths and agar:
Nutrient agar, Luria-Bertani broth and agar, tryptic soy broth and agar, MacConkey agar, SS agar, EMB agar, MSA agar, and almost all types of selective and differential media can be safely autoclaved.
The components of each of these specialized media can withstand high heat and pressure. - Solutions and buffers:
Buffers like PBS (Phosphate-buffered saline), tris buffer, sodium acetate buffer, NaCl solutions, and water (Millipore, MilliQ, Distilled) can be autoclaved.
Pro tip: Always use heat-resistant glass bottles or containers when autoclaving liquid media. Loosely cap the containers to avoid dangerous pressure buildup inside the bottle.
Now let’s talk about what should not go into the autoclave.
Non-autoclavables: What Materials Should You Avoid?
When put under high heat, some lab items can harm the individual (you) and the instrument. Ultimately, if the autoclave fails to work it will delay everyone’s work.
Plus, not all materials can withstand autoclaving conditions, and autoclaving will cause them to degrade, leading to experimental failure.
Some of the important articles that should be avoided include:
Plasticware: Polyethylene (PE), polystyrene (PS), and most common plastics cannot be autoclaved due to their relatively low melting points and softness.
Glassware: Non-borosilicate and soda lime glassware are a no-no in the autoclave. They can crack or explode.
For plasticware and glassware, it is generally easy to distinguish what not to put in the autoclave as they normally come with labels. However, it is important to take extra precautions for media, chemicals, and solvents (see below).
Solvents: This one’s simple. Don’t autoclave organic solvents. These are things like acetone, phenol, and isopropyl alcohol. Similarly, don’t autoclave volatile compounds, especially if they produce toxic or harmful fumes.
Radioactive compounds: Some biology lab workflows require radioactive compounds. Their use is strictly controlled and they should never be autoclaved as that poses an extreme dispersal risk should the container leak in the autoclave.
Bleach and hypochlorite solutions: These solutions will be sterile and shouldn’t need sterilizing anyway (See the general rule below). Moreover, heating them will generate corrosive fumes, exposure to which will harm your lungs and generally be bad for you.
Media: Certain solutions and media can potentially lose viability under autoclave temperature. A list of such common items is provided below:
- Sugar and carbohydrate solution:
Although lower concentrations of sugar are generally autoclavable, high concentrations of glucose, sucrose, lactose, and maltose are not advised to be autoclaved due to the ability of sugar to caramelize down and lose its property. - Antibiotics and media containing antibiotics:
Almost all types of antibiotics like Ampicillin, Chloramphenicol, Tetracycline, and Kanamycin are heat sensitive and cannot be autoclaved. Media containing antibiotics also cannot undergo autoclaving. Generally, antibiotics are added aseptically later on to autoclaved media or after cooling agar down to 50°C. - Serum and media containing serum:
FBS, horse serum, etc., cannot be autoclaved as they contain protein which can denature at such high temperatures. - Vitamins, amino acids, nucleotides, lipids, enzymes, hormones:
These bioactive substances lose their viability and can break down into by-products leading to their loss of function. Any media containing these shouldn’t be autoclaved. - Acids and organic solvents:
Acids like Acetone, Ethanol, and Chloroform are highly flammable and possess a high risk of explosion or fire.
For easy reference, we’ve created a quick guide to autoclavables vs non-autoclavables in the table below. Why not stick a photo of it in the back of your lab book?
Table 1. A summary of autoclavable and non-autoclavable lab materials.
Autoclavable | Non-autoclavable |
Pipette tips and tip boxes PP-based plasticware Centrifuge tubes Surgical instruments Borosilicate bottles Water Growth media Salt solutions and buffers Stainless steel lab items such as spatulas and spoons | PS- and PE-based plasticware |
A General Rule: Is it Sterile Anyway?
The whole point of autoclaving something is to kill microbial growth to prevent it from interfering with your experiments.
Most of the non-autoclavables listed above are naturally sterile and used to kill microbes (alcohols, bleach, etc.)
Therefore, they will never need to be autoclaved!
Before putting solutions in the autoclave, always think:
Can anything grow in it?
Does it kill microbes anyway?
If the answers are “no” and “yes,” respectively—don’t autoclave it.
What Should You Do if You Autoclave Something Bad?
Mistakes happen in labs. If something non-autoclavable is put under high heat and pressure, it can lead to degradation or contamination risk. Mistakes during autoclaving are manageable if prompt actions are taken to ensure the safety of equipment and individuals.
Some actions that can be taken during such situations include:
- First, don’t panic. If you have put something non-autoclavable, don’t immediately open the autoclave without checking the pressure and temperature conditions. Switch the autoclave off, let it cool, let the pressure release to zero, and ensure you do not open it at high pressure as it can cause significant burns. Always remember, your safety comes first;
- If the temperature and pressure are near ambient, put on some gloves, open the autoclave, and remove the articles safely;
- Check for the nature of the item that was unsuitable for autoclaving. I.e., if it was media, chemical, or plasticware. Take guided actions with the help of a safety officer;
- Check for suspicious fumes and odors and report anything you’re not satisfied with to your safety officer;
- Ensure the autoclave chamber is clean to prevent further damage or accidental re-autoclaving of incompatible materials.
Your Guide to Autoclavable Materials Summarized
It is important to know the basic properties of materials and solutions before putting them in the autoclave to be safe from any risk of damage and always avoid articles that are heat sensitive.
By following the right protocols, we can ensure effective sterilization of your lab equipment using the autoclave.
Further Reading:
- Easy ways to wreck your autoclave.
- The chemistry of the autoclave.