Application Note – Microbiology N.2 – The best use of micro-wave oven to melt microbiological media
The microwave oven is recommended for saving time during microbiological culture media preparation when it is necessary to have available melted media in a few minutes.
The microwaves cross, without heating, air, paper, wood, earth, china, glass, plastic material and are absorbed by the media and other organic and inorganic substances.
General recommendations
The microwaves are reflected from metal objects like steel, iron , aluminum , etc.; do not use metal containers o metal caps.
The door and air vents can become quite hot. Take care not to touch these areas.
To avoid damaging your oven, never operate it when empty.
If you leave the media in the oven too long, it will dry and burn.
Make sure that the container is suitable for use with a microwave oven. Do not use metal containers.
Installation
Position the oven on a flat , horizontal surface. Keep it clear of any source of heat or steam.
Check that air can flow freely around it. Leave sufficient space between the oven and the wall: 5 cm at the sides and at least 10 cm at the back.
Never lay anything on the oven which could block the ventilation orifices at its back.
Cleaning
A damp soapy sponge should be used to clean the inside and outside of the oven.
The periphery of the door and oven must always be clean.
It is not recommended to use abrasive products, alcohol or thinners which could damage the oven.
Hot vinegar is suitable for wall wiping.
Melting of agar media
a. Use glass Erlenmeyer flask o Pyrex bottle with plastic screw cap. Never use metal cap.
b. The cap must never be hermetically closed. It must be always unscrewed. An hermetic closed container could explode.
c. When the medium starts to liquify , open the oven door and mix the content of the glass container to obtain an uniform temperature inside the media.
d. When using small containers ( 25, 50, 100 ml ) include them in a bigger larger vessel containing water to obtain a more regular and progressive heating.
e. When using test tubes, include them in a Pyrex beaker containing water. Be sure the test tube caps are not made of metal ( plastic caps or cellulose plugs should be used ).
f. The heating time should be selected by experience using different amount of media.
