We tested taking long exposure pictures with the Thermal Fishing Bob using Glow Doodle and a paddling pool. We first filled the paddling pool with cool water. And moved the thermal fishing bob around which painted the pool with green light. The first two pictures show the results of that test.
We then added one bucket of water at temperature of 97.6. The fishing bob changed to a light yellow color. See picture below.
To create a stronger effect we added two more buckets of 97.6 degree water changing the fishing bob bright red.