| 1 | The red colours are manufactured using strontium. | |
| 2 | Others decay more slowly, like some cesium, iodine, strontium, and argon. | |
| 3 | Lee-Thorp and her colleagues measured the levels of two isotopes of strontium, an element found in soil. | |
| 4 | The teal stars are made of a barium nitrate mixture and the red stars are a blend of strontium salts. | |
| 5 | Strontium was introduced at this time as well, which serves to strengthen teeth and reduce sensitivity. |