>(Re. Klaus: I scanned a glass cuvette, it starts blocking Uv at 260 nm, a
>bit curious since I thought that Crawford of The Keepers..claims glass
>starts blocking at 360 nm, maybe different qualties block differently,
>I'll look into that)
>
In my younger days I used to work for an electro optics firm (Spectrolab). We made solar simulators using mostly Osram Xenon Arc lamps. The bulbs, the smallest of which were 2500 watts, were made of Supersil quartz glass. This was so they would transmit the short wavelength UV. They were under pressure, something like 20 atmospheres, if I remember correctly, and the real danger with these bulbs was that if one exploded, and penetrated your body, the glass could not be seen on x-ray. X-ray bulbs are made of quartz glass as well. Glass can have varying degrees of quartz and silca mixed, it can also have lead in it which I imagine would not be good for making x-ray bulbs.
Dick
>Date: Fri, 28 Feb 1997 11:08:19 +0100 (MET)
>From: Cor Breukel <<cor@ruly46.medfac.leidenuniv.nl>
>Subject: Re: UV transparency/attempt to explain a spectrophotometer (fwd)
>X-Sender: cor@ruly46
>To: Judy Seigel <<jseigel@panix.com>
>Cc: ALT-PHOTO-PROCESS-L@skyway.usask.ca
>Comments: "alt-photo-process mailing list"
>
>On Fri, 28 Feb 1997, Judy Seigel wrote:
>
>>
>>
>> On Thu, 27 Feb 1997, Cor Breukel wrote:
>>
>> > Finally I'am able to contribute some hard data myself..;-).. I did some
>> > testing last week with different (clear) film base.
>Sniperdesnip
>
>> Cor, do I understand correctly that you have a machine by which you can
>> DIAL IN the wavelength, like dialing a radio????.... Would you like to
>> have the next "Meeting of the List" at your laboratory?
>
>..Oh oh, got myself in trouble now..but that's wat happens if you want to
>play with the big boys and girls..;-)..
>
>Ok, let me first try to explain a spectrofotometer as clear as possible:
>(had to dig up the manual again to refresh my memory..feels like all those
>experienced contibutors when they say..back in the sixties..12 years ago
>when I started..or when I heard my (grand)son say..:-) )
>
>A spectrophotometer is a maschine which uses 2 lamps (a Qaurtz-Halogen for
>visible and a Deuterium lamp for the UV spectrum). Via a series of
>inginieus mirrors, filterwheels etc. this maschine is capable of producing
>a ray of light with a single wavelenght (+ or - 0.5 nm I thought). This
>"ray" is send through a little "chamber" called cuvette (about 10*5*40 mm)
>made of quartz (doesn't block UV) or glass: blocks UV
>
>(Re. Klaus: I scanned a glass cuvette, it starts blocking Uv at 260 nm, a
>bit curious since I thought that Crawford of The Keepers..claims glass
>starts blocking at 360 nm, maybe different qualties block differently,
>I'll look into that)
>
>So this "single wavelength ray" hits the cuvette and what's in it (usualy
>a solution, in this case a piece of clear film), and "behind' the cuvette
>a sensor measures the loss so to speak, it gives a read out in either
>Transmission (the energy that got through) or Absorbance (the energy that
>was left behind, got blocked) which (I think) is equal to Density.
>You can use this maschine either to read the Ab. of a single wavelength,
>or a continous spectrum, which I did for this filmbase test. I have no
>idea if one could test the specific wavelengths of different processes (I
>imagine I could make tiny pieces of say cyanotype paper, "read' a
>wavelength, thus exposing this tiny bit of cyanotype paper with this
>particulair wavelength)
>
>Hope this makes it a bit clear, but bear in mind that I am no specialist
>in this field
>
>
>>
>> It isn't clear to me, however, whether that 20-30 min. for cyanotype is
>> the reduced printing time, or the 312nm printing time. Our school
>> printing time averages around 10 minutes for regular blacklight bulbs,
>> mine at home is usually less, so that sounds long -- though maybe there
>> are other structural factors.
>
>..I didn't express myself clear enough: The Xray film I use has a blue
>base, blocking UV light from 360 nm down. The UV box I use has a Quartz
>"tablet", 4 special UV tubes beneath, resulting in a (peak)wavelength of
>312nm, well into the "blocked" area of the clear blue base of my film,
>thus longer exposurer than needed (I'am in the process of building a
>"normal" UV light box)
>
> >
>> But that's not why I'm writing -- have you described your procedure in
>> enlarging to the Xray film, and I just missed it? If not, would you fill
>> in some details about which kind of film (just had a chest X-ray, film
>> as big as the New York Times, mammograms only as big as Readers Digest),
>
>My procedure: I enlarge 6*6 negs onto Konica A2 20*40cm Xray film (yes
>freeby outdated), develop in D19 (increasing contrast), contactprint this
>positive, and develop in D19 again. Have to check the Dmax still though,
>but I obtain good VDB and cyanotype prints (at least I think that they are
>good, I'll see in Bath..;-) ). Also used dig,. 35 mm negs, but tht's
>another story..
>
>Btw this film is quite fast, when I use it in my Pinhole camera, I rate it
>at 800-1600 ASA
>
>
>>
>> And here's an afterthought -- is there any way this ingenious device
>> can be persuaded to read the sensitivity points of emulsions?
>
>..see above
>
>>
>> Thanks again,
>>
>> Judy
>>
>>
>
>Cor Breukel
>http://ruly70.medfac.leidenuniv.nl/~cor/cor.html
>"The Infrared Gallery"
>http://ruly70.medfac.leidenuniv.nl/~cor/ir-gallery.html
>
>
>
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