How do you safely heat a test tube?
Hold the test tube at an angle. Point the test tube away from yourself and all other people. Heat the test tube gently from the top of the substance being heated, and always wear safety googles.
If you heat the test tube from the bottom, any liquid can turn into a gas. The gas will rapidly expand shooting heated liquid out of the test tube like a cannon. The heated liquid can cause great damage especially if the liquid heat another person in the eyes.
Heating the test tube at the top allows any gases formed to escape without forcing liquids on top of the gas out of the tube.
Heating the tube at an angle reduces the pressure on the heated substances again allowing the gases to escape harmless into the air.
Accidents happen even heating the test tube gently at an angle can result in heating liquid being shot out of the test tube. This is why the test tube must be pointed away from any other person and why the experimenter must always wear safety glasses.
PS also be sure that an emergency eye wash station is available.
Remember Accidents will happen.