Posted on

The History of Photoluminescence

The History of Photoluminescence

American PERMALIGHT® is well known for our PERMALIGHT® Photoluminescent Egress Path Marking System, as well as our other photoluminescent life safety products. The phenomena of photoluminescence (or “glow-in-the-dark”) have been documented since the early 17th century and have since evolved into a source of reliable lighting and egress path markings in the modern-day Life Safety industry as well as other uses you’ve seen in day-to-day life.

Learn about photoluminescence, where it was first documented in history, and where we are now with this fascinating material.

Some Facts About Photoluminescence

  • Photoluminescence by definition is the emission of light from a molecule or atom that has absorbed electromagnetic energy.1
  • In simpler language, photoluminescence works by being activated by ambient or direct light and visibly releases light back when viewed in darkness.
  • Photoluminescence is also known under the terms “glow-in-the-dark,” “self-illuminating,” and “luminescence.”
  • Photoluminescence is not created by a chemical reaction, nor does it contain radioactive compounds. Photoluminescence works by exposure to light.
  • Photoluminescence is often abbreviated as PL.2

The Beginning of Photoluminescence

Photoluminescence was first officially observed and documented in 1603 by Vincenzo Cascariolo3 in the outskirts of Bologna, Italy in a naturally occurring stone called baryte (also spelled “barite”). This glowing stone, nicknamed the Bologna Stone (also Bolognian Stone), was witnessed to emit light after being treated by heat and being exposed to sunlight. This stone was prized and sought after to be studied for its mysterious glowing properties.

Baryte Mineral
Ivar Leidus, CC BY-SA 4.0, via Wikimedia Commons

It was discovered in 1669 by German physician Hennig Brand4 that the element phosphorous is what causes photoluminescence. The presence of phosphorous is the reason that the Bologna Stone glows under certain circumstances. All photoluminescent materials contain some kind of phosphor to create their signature glow.

Photoluminescence in Modern Times

Photoluminescence is now generally made from two of the main factory-produced phosphor compounds – Zinc Sulfide or Strontium Aluminate. Current photoluminescent products are made with these pigments to produce the variety of non-radioactive glow products that are available for purchase on both the consumer and commercial levels.

Glow comparison over time: Zinc Sulfide (left) next to Strontium Aluminate (right)
User:FK1954, CC0, via Wikimedia Commons

Zinc Sulfide5 is an early generation manufactured photoluminescent pigment. It is cheaper, has less efficient photoluminescent properties, and can be found in most consumer-level glow-in-the-dark products such as novelty stickers, toys, and more. It is also used in some commercial applications such as in cathode ray tubes. Zinc Sulfide can be activated with other materials (silver, manganese, or copper) to create different glow colors and intensities.

Strontium Aluminate6 is currently the latest and longest-lasting and brightest phosphor compound commercially available. It glows 10 times brighter and 10 times longer than copper-activated Zinc Sulfide. Strontium Aluminate phosphors produce green and other hues. Green Strontium Aluminate is used in applications that demand a high and consistent level of glow because the human eye can best perceive the greenish wavelength in the dark.

Sample of Strontium Aluminate
Splarka at English Wikipedia, Public domain, via Wikimedia Commons

Strontium Aluminate is considered non-toxic and biologically and chemically inert. Both Zinc Sulfide and Strontium Aluminate are non-radioactive.

PERMALIGHT® Photoluminescent Life Safety Products

PERMALIGHT® Photoluminescent Egress Path Marking System products and our other photoluminescent products are made in our factory in Germany from the highest-quality Strontium Aluminate in the right mixture and formulation. This ensures a long-lasting glow that has been lab-tested in an ISO 9001-environment and certified by Underwriters Laboratories, Inc. to meet building code standards.

Our PERMALIGHT® products are designed to glow for hours after proper activation to ensure safe exit to safety when properly activated and installed.

Trust PERMALIGHT® when it comes to photoluminescent egress path marking products for your Life Safety and Building Code-Compliant needs.

Shop Online at American PERMALIGHT®

American PERMALIGHT® | Guide & Protect | Since 1988