Self Luminous Exit Sign Comparison
Self luminous exit sign comparison
Before creation of the first self-luminous exit sign, scientists discovered that crystallization could cause luminescence. Once that phenomenon had been discovered, it motivated the creation of a new type of buoy. Each of the new self-luminous buoys was encircled by several rings made from a strong glass containing mercury.
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Mercury in exit signs
The mercury used had been made subject to a good deal of pressure. Therefore, as the ocean waters moved, it would hit the tubing and become electrified. That electrified mercury began to glow and helped to guide ships away from a rocky coast. Phosphorus was another material that could produce a glow. However, a second property linked to phosphorus lacked the appeal of a glowing object. It was the unpleasant smell produced by that element, one that resembled the odor normally associated with garlic.
Development of radioactive derivative
While conducting an experiment, the scientist Robert Boyle found a way to disguise the offensive odor without doing away with the element’s luminous property. He put bits of phosphorus into different solvents: cinnamon oil, clove oil, and alcohol. He then made a significant observation. He noted that by diluting one part of phosphorous in a million parts of solvent he did not destroy the element’s ability to keep glowing.
Yet the glowing phosphorous did not produce beams with a uniform intensity. Boyle himself indicated in his notes that each of them seemed to tremble. He also wrote that the glowing phosphorous would sometimes blaze out, emitting almost shocking flashes. Such observations indicated that a different luminous material would need to be used for consistant lighting applications.
Discovery of radiation
For a while, efforts focused on using zinc sulfide in exit signs that were to go at an entrance/exit. However, that compound produced a fairly weak afterglow. The discovery of radiation seemed to suggest the possibility of using radioisotopes. However, after the public learned more about the dangers inherent to prolonged exposure to radiation, that idea also had to be laid aside. Today the makers of self luminous exit signs make use of the accumulated knowledge regarding the chemistry of strontium oxide aluminates.
Afterglow of radioactive substances
Signs that utilize the chemistry of strontium oxide aluminates have an afterglow that is ten times brighter than that produced by zinc sulfide. Moreover, that chemistry can be used to make glowing objects with a higher level of luminescence. That improvement results from changes in the selected activation time. That period has now been lengthened.
The combination of developments and changes outlined above led to introduction of aluminum photo luminescent exit signs. That approach eliminated concerns about the hazardous nature of certain substances. At the same time, it allowed for improvements to the glowing objects placed atop various doorways. Each of them displayed a higher level of one particular property, something called light fastness.
Luminescent exit signs
In comparison with other known approaches, utilization of aluminum photo luminescent exit signs seems to use the most satisfactory product at the present time. Of course, manufacturers have not shut down their research and development departments. Experimentation conducted in such a department could lead to creation of an even better type of self luminous exit sign.