Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "John Craddock" <John.Craddock@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, September 26, 2006 4:07 AM
Subject: RE: [Homebrew_PCBs] Re: UV Light Sources


>
>
>> -----Original Message-----
>> From: derekhawkins [mailto:eldata@...]
>> Sent: 26 September 2006 10:05
>> To: Homebrew_PCBs@yahoogroups.com
>> Subject: [Homebrew_PCBs] Re: UV Light Sources
>>
>>
>> >FYI in the English language we spell "vapor" as vapour, so a search
>> >missed it
>>
>> Missed what? Searching on >mercury vapour< gives another set of hits
>> including this;
>>
>> >>DO NOT break the outer glass shell of a mercury vapour lamp! It
>> >>will radiate a lot of short wave UV (UV-A) which is dangerous for
>> >>eyes and skin, and it generates lot of ozone (O3). Good results
>> >>could be obtained without breaking the outer glass shell.
> That was precisely the reason for my question (see the first post on this
> thread). I understand from my web searching that UV-A is the radiation
> band that actively polymerises the UV resist. I further understand that
> the more intense the UV-A radiation is the quicker the polymerisation. I
> have also read that the quicker the exposure, the better is the definition
> achievable. Seeing as the exposure unit would be fully enclosed, I don't
> see a problem with the eyes and skin bit. Anyway, from the research that I
> have done, it seems that the dangerous radiation bands are UV-B and UV-C;
> so your quotation is quite incorrect on that point but the UV-B and UV-C
> also is unblocked by breaking the glass filter. So the recommendation in
> that excerpt is appropriate for some purposes. However it is out of
> context so I cannot tell. The so-called solariums (facial tanners) rely on
> UV-A as their active radiation ingredient so it cannot be too harmful.
> Ozone has got me a bit worried though.

Several people remove the outer envelope, it has to be done with sodium
vapour lamps anyway. I think that the Hg lamps will emit a lot of UV as it
is. I used to get a lot of ozone from EPROM eraser tubes (germicidal tubes),
so I'm used to it. It gets converted to O2 quite quickly, and the main
effect is as an irritant. We will only have it on for a few minutes at a
time, so I can't see it being a problem.

They used to pump O3 throught the London Underground system at night, to
kill germs. Perhaps they still do. I think a carbon filter will remove O3,
they are used on photocopiers, which used to emit lots of ozone. At any
rate, the old Xerox ones did - I used to work for Rank-Xerox (UK). It was
produced by the corotron which charged the photoreceptor.

Leon
--
Leon Heller, G1HSM
Suzuki SV1000S motorcycle
leon.heller@...
http://www.geocities.com/leon_heller