Graeme wrote:
>
> Fred Nieman <[email protected]> wrote in
> news:[email protected]:
>
> > Graeme, I respectfully differ on both points you make.
> >
>
> Fair enough (sorry to dredge up this old thread, I've not been online for a...
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> We had at one point been
> discussing the "fluoro" glow from watches etc. (i.e. glows once the
> stimulating light source is removed) and this may have been the type of
> colouring/dye that is difficult/impossible to produce in a commercially
> viable weaving process.
1) Agreed. I think the distinction here is between
- fluorescence, ("Day-Glo") where electrons in the active compounds in
the pigments absorb UV light and jump to a higher energy state, and
visible light is emitted when those electrons jump down to a lower
energy state and emit a light of their own);
and,
- phosphorescence ("glow in the dark") where electrons in the pigments
in effect soak up the energy of the light falling on them and then
re-emit the stored energy later as a glow.
(refs: year 12 physics, plus inter alia (to check the terminology)
http://mineral.galleries.com/minerals/property/fluoresc.htm,
http://mineral.galleries.com/minerals/property/pleochro.htm)
2) Actually, I guess in lay terms, there are two kinds of
"phosphorescence"
- the "glow in the dark" effect, and then
- stuff that glows without a prior external energy source (like
radioisotopes, or freshly shaved anglo-celtic male legs).
Phosphorescent fabrics? Well, there were those t-shirts around that
changed colour depending on the heat of the bit of you they were
touching, and I for a long time had blue shoelaces in my field hockey
shoes that incorporated micro-balls of blueberry smelling stuff. I'm
sure that since there's the kind of technology around today to perform
feats that even 20 years ago might have just seemed like science fiction
(nanotechnology, quantum computers, George W Bush as POTUS), "glow in
the dark" phosphorescent fabrics, but there's just no demand for the
supply. (I guess this goes a whole lot than just double for
lycra-with-radioisotope-microthingies... but who knows whether the big
hit of the next Summer Collections from Milan will be the new "ionising
radiation chic"...)
> I take your point about "day-glo" (or whatever) clothing being brighter
> than normal clothing, but the percentage of the original light given off
> again by the clothing is *very* low. On a dark night, if you are outwith
> the beam of a car headlights the clothing will be still be fairly
> unnoticable compared to even a cheapy LED light. You are far better off
> with some sort of reflective material, e.g Scotchlite. That also relies on
> being in the beam of another light source but it will make you more visible
> for a given amount of light.
3) Again, 100% agreed. Why can't I buy a (for example) Netti
water-resistant jacket that,
* instead of being (daytime very visible) with about 0.5 cm$B%$(B token
Scotchlite (nighttime, looks like a dull grey, and I'd be better off
wearing a plain white jacket)
* is either;
- made of a fabric with fluoro yellow and Scotchlite alternating
stripes,
or;
- made of a fabric that is Scotchlite-like reflective, but dyed a fluoro
yellow pigment?
<curses, and shakes fist, at market forces>
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> Fair enough (sorry to dredge up this old thread, I've not been online for a
> while). I think any problem with my previous statements probably stems from
> the fact that the original conversation I mentioned covered about 6
> different topics (all the best ones do).
Umm, I was only going to mention 3 vaguely on-topic topics in this
reply, but I'd like to make it one of the "best ones"... so here goes:
4) why are "Bianchi" bikes traditionally a pastel blue-green (roughly R:
129, G: 255, B: 215) when "bianchi" in Italian means "(the) white
ones"?
5) Philip Ruddock appears to be an intelligent and compassionate person,
so how does he manage to sleep at night?
6) If pneumatic tyres and the modern bicycle chain had been invented 100
years earlier, would we all be riding bicycles instead of driving cars,
or would we be riding motorcycles instead of driving cars?
>
> Cheers,
>
> Graeme
xx
p
