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A vacuum mixer is equipment that allows the operator to mix compounds under vacuum to limit excess air and prevent bubble formation. These mixers are available from many companies for scientific research, food service, and medical uses. These companies also supply replacement components and kits to expand the functionality of their equipment, such as different styles of mixing paddles for different applications. It may be possible to rent a vacuum mixer for a specific application if purchasing one is not practical.
The vacuum mixer includes a central mixing drum with paddle insert, designed to be installed inside a casing to pump air and create vacuum conditions. The operator can adjust the level of vacuum and pressure for different applications. When in operation, the mixing paddles rotate around a central assembly, thoroughly agitating the contents of the mixer. It is possible to keep the materials under vacuum during the whole process, if necessary.
One of the uses of a vacuum mixer is the preparation of cements, amalgams and other materials for medical applications. These cements can fail if they contain air bubbles or if they are not fully mixed. Vacuum mixing prevents the formation of air bubbles and completely homogenizes components such as powders and alginates to create a smooth, even mix with a uniform texture. This will work better than a hand-mixed preparation, which can be prone to blisters and other inclusions.
Mixing paddles can work in a variety of ways. Many designs include an external squeegee to continually clean the sides of the mixer. This forces the material back into the mix to fully integrate and prevent sticking. As the blade rotates, the vacuum conditions prevent bubbles from forming. The device may also have a degassing function to release any gas that forms as a result of mixing reactions.
Many vacuum blenders adhere to strict standards for food and medical equipment because they are often used in the production of products that humans eat or come into intimate contact with. Devices can be completely disassembled and sterilized, and can come with components that can be replaced as needed to resolve contamination issues. Operators can also use test swabs to collect samples from inside so they can check for bacteria and other sources of contamination. In some settings, the vacuum mixer may also be subject to inspection by government officials responsible for setting and enforcing health codes.