GLOW IN THE DARK PIGMENT WATERPROOF TYPE
1. Put both waterproof pigment and non-waterproof pigment into water for 10 minutes.
2. Test the PH value with PH test strips.
3. PH test strips in the left beaker shows test value about PH=14, which means the pigment was destroyed by water and the solution turns alkaline, and when we put it in dark place it does not glow any more.
4. PH test strips in the right beaker shows test value about PH=7, which means the pigment is not destroyed by water and it still glow when we put it in dark place.