> It is UV RADIATION! The part of the spectrum one can see is referred
>to *light*. What cannot be seen is *radiation*.
A point I often make to my students is that light is the part of the spectrum
of electo magnetic radiation that one can see.
The international standard definition of light is'the aspect of radiant of which
a human observer is aware through the visual sensations which arrive from the
visual stimulation of the retina of the eye'.
Or, as that excellent Kodak book 'Photographic Materials and Processes' has it
', light is that energy that permits us to see'.
It goes on to say 'Thus it is proper to speak of ultraviolet radiation and
infrared radiation but not ultraviolet light and infrared light. The popular use
of such phrasesas black light and invisible light to describe such radiaition
make it impossible to determine what type of energy is being described, and they
should be avoided.
I used to take the line that it was better to go OTT in terms of safety with
students to avoid accidents but now I think that it is far better if one
understands the principles and can take appropriate precautions. I am not sure,
for example, that small leaks of reflected UV from a lightbox are going to have
any deleterious effects at all espcially when one takes the inverse square law
into account.
Another point is that as different alternative processes react to radiation at
different wavelenghts, some of which we can see, an ultraviolet tube is perhaps
not the ideal.
It might be an idea if we were to establish a table showing the output of
various light sources in nanometres and energy compared with the sensitivity to
the different wavelengths of the sensitisers with which we are working, and the
effects of those wavelengths in terms of health.
If there were such a table in the archives we could refer people to it or keep
it in our files so that we can send it to anyone who asks.
We might do the same with toxicity and by so doing still some of the irrational
fears that inhibit some peoples' enjoyment of alternative processes. I have no
such convenient reference on my bookshelves. And I realise from some of Dick
Sullivan's comments that some of my fears have been irrational and that comments
from ex cabinet making apprentices have entirely changed my attitude to oxalic
acid.
Terry King