Fluroescent colours

[matty2670]

How are fluroescent or 'DayGlo' colours produced? What is added that makes them much brighter than ordinary inks or paints? (Sorry if fluroescent is spelt wrong, I couldn't be bothered to go and get the dictionary...)

[Clanad]

From The Akron Section of the American Chemical Society:
Fluorescent dyes that exhibit daylight fluorescence are well known; in fact some of these dyes were discovered in the late nineteenth century. It was a fascination with the fluorescence phenomenon that led Bob and Joe Switzer, the founders of Day-Glo Color Corporation to experiment with ways of combining certain dyes and resins to produce colors far brighter than normal. Initially, these new colors and effects found their way into magic shows, stage shows, movie promotion posters and bright signal panels used by the army. The early preparations created bright �eye popping� color effects but lacked sufficient lightfastness to have substantial commercial usage. In the 1950�s, Day-Glo chemists discovered favorable polymer/dye interactions. A major breakthrough was the discovery of polymers of melamine, formaldehyde and toluene sulfonamide, or aminoplast resins. By dissolving the fluorescent dye in a molten aminoplast, cooling, and mechanically grinding; a fluorescent pigment is formed. The fluorescent pigment has a twofold advantage over a dye. One advantage is that the fluorescent dyes are now protected from the environment by a �polymer shield.� The second advantage is that colorant applications that were once forbidden due to solubility, migration, or lightfastness properties of the dyes are now accessible due to the superior physical properties of the pigment. This polymer technology later evolved to including polyester-amide based fluorescent pigments. Polyester-amides are useful as fluorescent dye-carriers into polyolefins...

[mycats]

so, that clears that up then rofl (sorry Clanad)

[Hippy]

The fluorescence works because like other coloured surfaces the Dayglo reflects visible light. in the normal way but the4 special dyes also absorb ultraviolet light, invisible to the unaided human eye, and then converts it to a lower wavelength and then emits photons in the visible spectrum. This means that the Dayglo stuff looks a lot brighter than it should because of more than the expected reflected light coming off.

There are some clever stage effects (dancing skeletons in the dark etc.) created by fluorescent paint and ultraviolet light in an otherwise dark theatre.

Some of the commoner colorants used are based on Fluorite (fluorspar), a calcium based mineral, after which the phenomenon is named. See http://en.wikipedia.org/wiki/Fluorite for more.

[matty2670]

Blimey!!! Much obliged to you