This shows that heat cannot readily flow in glass. Glass is a bad conductor of heat. Other bad conductors of heat are rubber, wood, cork, paper, bakelite, etc. You will notice that the handles on cooking pans are made of a plastic called bakelite. That is why you can hold a hot pan.
Water is also a bad conductor of heat.
Most of the metals are good conductors of heat. Most of the ionic compounds are relatively good conductors of heat. Most of the covalently bonded compounds are bad conductors of heat. In a beaker take a little water and start heating. Before the boiling point is reached, pour a drop of blue ink in the water.