Metering UV Exposures - Modern Actinometers?

holmburgers · Jun 1, 2011

This could be hare-brained, but I just stumbled upon some products that measure your exposure to UV radiation.

These are intended of course for beach goers avoiding sun burns, skin cancer, etc., but the potential for alternative printers is enticing!

Here are a number of products:

http://cgi.ebay.com/Oregon-Portable...130?pt=LH_DefaultDomain_0&hash=item2a0d4faa1a
- (http://www.oregonscientific.co.uk/ulimages/manuals2/EB612-UV888.pdf)
http://cgi.ebay.com/SUN-SMART-UV-EX...117?pt=LH_DefaultDomain_0&hash=item3a613515d5
http://www.google.com/products/cata...=X&ei=5p_mTfKfJ8rAgQekpaH2Cg&ved=0CGEQ8wIwBQ#
http://www.google.com/products/cata...=X&ei=5p_mTfKfJ8rAgQekpaH2Cg&ved=0CF0Q8wIwBA#

Even something as simple as this: http://www.amazon.com/HQRP-Keychain-Ultraviolet-Radiation-Indicator/dp/B004XMH9FU

The question is I guess, are they sensitive & accurate enough for reliable printing?

holmburgers · Jun 1, 2011

http://www.solarmeter.com/

These seem a bit more legit.

gmikol · Jun 1, 2011

Yeah...the ones in your first post all just seem to show UV Index, which is designed to predict skin damage from skin cancer. Not quite sure how it's computed or whether the 0-15 scale is log or linear or what.

The second post (Solartech)...that seems like a possibility. Seems like the Model 5.0 might be the ideal one for alt-printers. Not sure if the "HP" variant (up to 1999 mW/cm^2) would be necessary. Honestly, I have no idea what the power output of a BL tube or a Nuarc lamp is.

Thanks for the interesting links.

--Greg

nhemann · Jun 1, 2011

Interesting question so I did some reading (God save Wikipedia) BL tubes, which are mercury vapor lights, emit UV mostly (approx 90%) at 253.7 nm - which is below the measuring range for the 5.0. The Model 8.0 is just barely within range but it might not be so accurate that far to the left of the scale.

However, unless I am mistaken, these units read an instantaneous value - as opposed to a totalized reading so you would still have to measure your time value as opposed to exposing for "units" of light.

I couldn't find anything specific about a Nuarc but the seem to be just a different version of a Hg lamp so I assume a similar response.

gmikol · Jun 1, 2011

nhemann said:
Interesting question so I did some reading (God save Wikipedia) BL tubes, which are mercury vapor lights, emit UV mostly (approx 90%) at 253.7 nm...

I'm afraid Wikipedia may have led you astray on this one. UV-C (germicidal) bulbs emit in that range. Typical bulbs used for alt-process (BL, BLB, actinic/aquarium/reptile, grow-light, etc.), typically emit in the 320-450nm range(UV-B, UV-A and visible blue light), depending on the exact bulb type, as do most metal-halide and mercury vapor arc discharge lamps.

Glass absorbs much of the UV-B below 350nm...
Dichromate (carbon, gum) has peak sensitivity around 370nm, I think.
Platinum and Cyanotype have broader sensitivities, which can extend slightly above 400nm, I believe.

Hope this helps...

--Greg

Ian Leake · Jun 2, 2011

My vacuum frame came with a UV meter which was connected to a computer. The pair allowed the operator to dial in an unit-based exposure rather than a time-based one - the theory being that if your exposure is 500 'units' then this will allow for bulb warm-up and other variations of UV intensity. I don't actually use this because I replaced the original lamp with a more intense lightbox, but I'd like to explore these options at some stage.

nhemann · Jun 2, 2011

Greg,
Thats even more interesting - thanks for catching that and I stand humbly corrected - my confusion arose from the headings "black light" and "ultraviolet fluorescent lamps" (which I now understand to ba a tube with no phsophor coating at all) those interested can read the item here: http://en.wikipedia.org/wiki/Ultraviolet#.22Black_light.22 and here: http://en.wikipedia.org/wiki/File:Fluorescent_Black-Light_spectrum_with_peaks_labelled.gif

Getting smart was apparently a two step process today!

Greg, just out of curiosity, would the shorter wave length work or is it just out of the range to work in alt/plat processes? And again, thank you for correcting my error in research.

holmburgers · Jun 2, 2011

The 5.0 and 5.7 do look ideal, to my untrained eye. These are pretty expensive though, at about $169.

There are a number of $49 units too -> http://www.solarmeter.com/modelPUVM.html

They're in the form of watches and are intended for monitoring sun exposure. Again though, could the values be useful to alt printers? Hmmm... very enticing, this is.

gmikol · Jun 2, 2011

nhemann said:
...would the shorter wave length work or is it just out of the range to work in alt/plat processes?

I don't know if any of the common UV sensitive alt-processes (Pt/Pd, gum, carbon, cyano, kalli, etc.) have any sensitivity down deep in the UV-B or UV-C, because as a practical matter, it doesn't make a difference. Glass starts to absorb UV around 350nm (still in the UV-A region), and is essentially opaque to UV in the UV-B and UV-C regions. So unless you're going to get a contact printing frame that replaces the glass with fused quartz, it doesn't matter. UV-C is extremely dangerous to living tissue, and shouldn't be messed around with.

--Greg

holmburgers · Jun 2, 2011

This begs the question, where is the hard data on the sensitivity of these processes?

Does anybody have some fused quartz prisms to make some classic sensitivity curves?

I've emailed the comapny and briefly described the needs of an alt printer and what they would suggest.

Check this out... (there was a url link here which no longer exists) ...maybe someone should ask Nicholas about this, or perhaps he'll join the fray here and provide some insight.

Mustafa Umut Sarac · Jun 2, 2011

alt photo list is a good place to ask

gmikol · Jun 2, 2011

holmburgers said:
This begs the question, where is the hard data on the sensitivity of these processes?

The UV absorbance of dichromate is reasonably well documented. IIRC it is just a single strong absorbance peak around 370nm. Since there are so many different variations for Pt/Pd, I'm not sure if their sensitivities are all the same. Same for the difference between traditional and Ware cyanotype.

If someone had access to a UV-VIS spectrophotometer, it would be trivial to measure the various coating solutions...

--Greg

holmburgers · Jun 3, 2011

From Solar Tech:

Yes the 5.0 meter would be correct choice. The 5.7 is too sensitive and would go overrange in full sunlight. No the PUVMs don't pick up 370nm... only UVB sunburn rays. Best regards...

Anybody feel like dropping $170?

holmburgers · Dec 6, 2011

Looks like Solar Tech has added a new product to their lineup, the SunUVStation.

If a product like this could give you a reliable measure of the UV present at any given time, imagine the convenience of being able to make sun exposures with as much confidence as indoor exposures with UV-units.

The issue is whether the UV-Index is useful for determining alt-exposures. Here is a good description of the UV-index and how it is figured. You'll see that they are well below the useful UV peak of 370nm for printing, but, are these values consistently proportional to slightly longer wavelengths and thus able to predict alt-exposures?

Metering UV Exposures - Modern Actinometers?

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