Science Buddies: "Ask an Expert"

I am doing the project "measuring luminescence in glow - in the dark objects. In the materials list it says phosphorescent paint or paper (at least 2 different types). By type do you mean color or water based vs solvent based? I am having a hard time figuring out my independent variable. Also, any suggestions on how to measure brightness objectively

Hello and welcome to the forums

I looked into phosphorescent papers and paints, and it appears that they are made with different materials. I would think that this experiment would be best with different pigments in the paint or paper. I found a vendor that sells the pigment by type of material, with "glow in the dark" time ranging from 20 minutes to many hours. These different materials are what I would test.

I'm not sure what you mean by "measuring brightness objectively". The experiment has you make a brightness meter. It measures brightness on a relative scale - are you asking about getting an absolute measurement? You can buy a commercial light meter for around $100 that measures lumens.

Let us know if you have other questions.
Keith