I have an ultra-freezer and I keep it at -70ºC. What is the most suitable concentration of glycerol? Anyone recommend porcelain beads? And a protocol for doing so, please.
"If you are going to store the bacteria in a special -80°C freezer, you should first snap-freeze the bacterial stock by dropping it in a container of liquid nitrogen. If you are storing the bacteria in a regular -20°C freezer, the bacterial stock can be placed there with no further treatment."