Firefly Flint Glow Safety Kit Marker Information

COOL Science Information Page

Firefly Flint Glows

We suggest you read all the information here before purchasing Firefly Flint Glows.
We are more than happy to answer any other questions you may have before you purchase - please use the Contact Us form on our website.

What are they?

The Firefly Flint Glow safety marker/survival tool has a ferrocerium flint rod which when struck with a steel blade will produce a shower of sparks for quick and reliable fire-lighting. It can also be used as an aid to identifying items in dimly lit situations, such as camping/fishing/orienteering kit marking, and a thousand other things we’ll leave up to you to think of! At the heart of every safety marker is a Swiss Trigalight™ GTLS, which is a completely self-contained power source - so they do NOT require batteries, neither do they need charging from sunlight or any other light source. The Firefly Flint Glow has a clear, polycarbonate outer case on one of which side is the flint rod; inside the case is the Trigalight™ which is a laser sealed borosilicate GLASS tube.

How does a Trigalight™ work?

The Trigalight™ is a Gas Tritium Light Source or GTLS composed of a laser sealed borosilicate glass tube which has a special phosphor coating on its inner surface and has been filled with a small amount of Tritium gas. As the Tritium decays the beta particles emitted by its nuclei strike the tube’s phosphor coating causing it to emit visible light. By varying the type and combination of phosphors used it is possible to create tubes which emit different colours.

The excitation of phosphors by electrons (beta particles) used in the GTLS is the same principle used to create the television picture in the old cathode ray tube televisions, only in the case of the GTLS the electrons are provided in the form of beta rays by the disintegration of the Tritium nuclei.

Tritium has a half-life of a little over 12 years so, as long as the glass core is not damaged the Firefly Flint Glow will emit light for many years.
Please note that descriptions you may have seen on other websites DO NOT apply here, there are NO manufacturers guarantees for the life-span of a Trigalight™ inspite of what other websites may claim!

How safe is a Trigalight™?

As the electrons produced by the gaseous Tritium are so low in energy, they are unable to breach a sheet of paper or to penetrate human skin.

 Safety Markers are NOT toys and are NOT suitable for children

Can a Firefly Flint Glow be damaged or stop glowing?

Although quite tough the Firefly Flint Glow is NOT indestructible, the GLASS Trigalight™ inside can be broken if the Flint Glow is dropped onto a hard surface or receives a hard blow; the outer case may not show signs of damage even though the Flint Glow has received a blow hard enough to cause damage to the GLASS Trigalight™ inside.
Breakage of the GLASS Trigalight™ is the only thing that will cause it to suddenly stop glowing and this is NOT covered by the manufacturers warranty - so please understand that if you break the tube we will NOT give you a refund or a replacement.

What colours are there and how bright are they?

This is a list of the colours we can supply (subject to availability) and an explanation of the perceived brightness:
Green, Yellow, White, Orange, Ice Blue, Red, Pink, Purple, Deep Blue

Do all of the colours appear to be the same brightness?

The simple answer is NO they do not, and the biggest reason for that is the human eye! It does not have a linear response to colours and this is why we perceive some colours to be brighter than others. The light coming from a green laser will appear to us to be very much brighter than the light coming from a red laser with the same output power; so with the Flint Glows there is quite a big difference between how you will perceive the colours to which the eye is most sensitive and to which the eye is least sensitive.

So; which Firefly Flint Glow will look the brightest, and which the dimmest?

By far the brightest looking Flint Glow is the Green and the dimmest the Deep Blue; this is because Green is roughly centre of the human eyes visible spectrum, as you approach the upper and lower limits sensitivity falls off sharply. If you consider the Green as the brightest perceived then Deep Blue will only appear to be about 15% as bright as the Green, Yellow is close to Green and is seen as about 80% as bright as the Green.

The list of colours shown above was compiled by us when looking at the Flint Glows in the dark as what we perceived the order of brightness to be, from brightest (left)  to dimmest (right); and although there is a large difference between the brightest and the dimmest, between some of the colours it was difficult to agree on exactly the order they should be arranged in, if you do some searching on the Internet you can find numerous lists of perceived brightness, some agree with ours and some differ slightly.

The important thing is: if the brightness IS important then you should select Green or Yellow - if it’s not then pick a colour you like but expect it to NOT appear as bright.

What kind of brightness can actually be expected?

As stated above, Firefly Flint Glow safety markers are designed as an aid to finding items in dimly lit situations - they are NOT torches so they will NOT light up the room, or give you something to sit and read by.

How bright they will actually appear to you will also depend on how well dark-adjusted your eyes have become, for example: if you go from a brightly lit situation into the dark and look at your Flint Glow it won’t appear anywhere near as bright as it would if you’d been sitting in the dark for say 10 minutes and then looked at it, it takes time for your eyes to adjust to a darkened room.

To summarise, the brightness and colour contrast of the Flint Glows can seem very different depending on ambient lighting conditions and of course a person’s perception of colour is very subjective.

How much should I rely on the colours and apparent brightness of the images I can see on the website?

This question highlights a problem you will always come across when trying to buy something from the Internet based on how it looks; in this case the colour and how bright it appears.

If you look at the apparent brightness of the different colours on the website they all probably look about the same brightness, why is this? Firstly, when taking the photographs the camera was set to a bulb (or timed exposure) setting so as to obtain an image that was bright enough to be useful. Secondly, cameras, whether film or digital based have a different response to colour sensitivity than the human eye; it is impossible to show how bright these will actually appear by showing you a photograph on a computer screen.

As for the colour it is impossible to give you an accurate representation of how you will actually see the colour, a full explanation of why would be very long but is basically as a result of the colour gamut’s of the different technologies used in bringing you the colours over the internet versus the human eye; so use the colours shown in the images as a rough guide only.

Some of the colours actually look quite similar to each other in real life, the Deep Blue is supposed to be a rough approximation of the colour of an old black-light lamp (blue with a hint of purple) and looks quite similar when compared to the Purple Flint Glow which may not be apparent on the images, where it appears more blue. So as we said, please use the images as a rough guide only.

For a brief peek at this fascinating subject see Colour Perception in the COOL Science Blog.


  • The Firefly Flint Glow:
    • Length: approximately 44 mm
    • Width: approximately 10.5 mm
    • Depth: approximately 14 mm
  • The internal Trigalight™:
    • Length: approximately 22.5 mm
    • Diameter: approximately 3 mm
  • Stainless steel split ring:
    • Outer diameter: approximately 22.5 mm

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