Place a pot containing about 2 inches of water on a hot plate and start heating.
Add tubes or bottles as soon as the heat is turned on, while the temperature is safe for placement of agar tubes or bottles.
Prop up the tubes or bottles so that they do not slide or slip sideways.
Loosen the caps slightly on the media tubes or bottles. Use gloves or tongs, if needed.
Boil for 10-15 minutes and until all the agar is melted.
Shut off the heat.
Allow the agar to cool to about 50 degrees C. Agar solidifies around 43 to 44 degrees C so you cannot let it get too much below 50.
Remove the cap from the agar tube or bottle carefully, wearing gloves to insulate your fingers.
Do not touch the mouth of the bottle or tube with your fingers.
Lift the upper lid of each Petri dish, one at a time, and gently pour the medium to cover the bottom. Add enough to cover the bottom of the dish and then just a little more.
Let each plate cool to solidify the agar. It takes 15 to 20 minutes.
Invert each plate carefully and label the bottom with the permanent marker. Label each Petri dish with the date and type of medium for reference. When plates are inoculated (e.g. streaked with microbes) other identifying characteristics are noted as required, e.g. dust sample, water sample, etc.
Store plates inverted (top lid facing downward) for up a week or more. It is best to use the medium within two weeks or less.