UV Source - Reflection Between Gaps

[eumenius]

Ah, that's what I thought about - low transmission of short UV rays through regular glasses, and 254 nm UV is indeed too dangerous (though cancer is too much for it, one gets faster burned to bones rather to contract cancer from mercury lamps). So the longer, softer UV is way much better for a regular darkroom, of course. I just remembered the UV tables with deep-violet UV filters in them, some are more than 18*24cm - each containing ~400W worth of 254 nm bulbs... we use it in our lab to visualize and cross-link DNA molecules. Ooops, that's the trouble with human beings

There are several reasons people do not use these type of tubes. UV radiation at the 254 nm range is extremely dangeous to human beings, and the risk is much greater than just skin and eye burns as it is known to be a cause of cancer.

And second, ordinary soda lime float glass, which most of us use in our contact printing frames, blocks a very high percentage of UV radiation below 350 nm, and virtually all of it below 300 nm, so not only is radiation at 254 nm very dangerous, it is also useless.

There are some speciality glasses, such as bososilicate, also known as fused silicate, and quartz, that transmit a very high percentage of light below 300 nm. But this glass tends to be very expensive and not easy to find.


Sandy

 

[Kirk Keyes]

There are some speciality glasses, such as bososilicate, also known as fused silicate, and quartz, that transmit a very high percentage of light below 300 nm. But this glass tends to be very expensive and not easy to find.

I think there is a bit of confusion here, just like at the start of the thread with the "anodized" aluminum...

I'm guessing that "fused silicate" should actually be called "fused silica", and it is not related to borosilicate glass. Fused silica is another term for quartz glass. It is composed of relatively pure silica, SiO2, which also found in the mineral quartz.

Borosilicate glass is the type of glass that is found in Pyrex and Kimax laboratory type glassware. Borosilicate glass conatins boron in addition to silica.

 

[sanking]

Yes, borosilicate and fused silica (quartz) are different animals. My apologies for the confusion.

But regardless there is little to be gained with speciality glasses of this type, and the risk to human beings of radiation below 300 nm is significant.


Sandy

I think there is a bit of confusion here, just like at the start of the thread with the "anodized" aluminum...

I'm guessing that "fused silicate" should actually be called "fused silica", and it is not related to borosilicate glass. Fused silica is another term for quartz glass. It is composed of relatively pure silica, SiO2, which also found in the mineral quartz.

Borosilicate glass is the type of glass that is found in Pyrex and Kimax laboratory type glassware. Borosilicate glass conatins boron in addition to silica.

 

[Mark G MacKenzie]

UV absorbing paint pigments

Hello. I am new to the forum and scanning for information related to building UV printing light sources. This thread is very interesting.

About painting the surface behind the bulbs. If you choose to do so you should expect a portion of the light to be re-emitted with a wavelength shift. This will be a varying amount of the light as much will pass through and be reflected by the metal (thus having a second pass and chance to be absorbed and re-emitted). Paints heavy with titanium dioxide are classic UV absorbers and re-emit within the visible spectrum.


You sometimes see this effect used to reduce reflected UV into exhibit cases housing sensitive museum/gallery artifacts.

Regards

 

[Neil Poulsen]

Just Finished Today

I just completed my uv source today. It works great. Again, thanks for all the input.

 

[photomc]

I just completed my uv source today. It works great. Again, thanks for all the input.

Congratulations Neil....hope you have a great time using it, Oh! And don't forget to post something for us to see