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UltravioletPhotography

Blocking Infrared Light with Copper Sulphate Solution.


colinbm

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One of the banes of the UV photographer is the all too present IR light.

First, I need to thank Reed F Curry for his help, encouragement & interest in this project, without his instigation this wouldn't have happened.

 

I have a number of Mercury vapour lamps, some are HID lamps, some are CFL lamps, some are of the UV Party lamp type.

My most powerful UV lamp is a 400 watt HID Party lamp, with a Wood's Glass outer globe, & others down to an 4 watt Fluoro UV Black light.These all output around 365-400nm of LW UV, BUT also some IR, which is difficult to attenuate completely. Glass filters are useful, but to attenuate the IR at the lamp is difficult because some produce a fair amount of heat, but usually under 80 deg C.

 

Reed suggested to use a filter cell with a solution of 12.5% (1/8) Copper Sulphate in water.

This is made by mixing small quantities of Copper Sulphate powder in water, until it will dissolve no more & the powder falls to the bottom of the mix. The mix is then filtered, then cut three times with equal amounts of water. That is, if you have 1 litre of saturated copper sulphate solution, add 1 litre of water to make a 50% solution. You can then cut this 2 litre mix with another 2 litres of water to give a 25% solution. Lastly, you can cut this mix with 4 litres of water to give an 8 litre solution of 12.5% (1/8) Copper Sulphate solution.

 

So I went about building a 40mm thick cell, first to fit a 24 watt Mercury HID lamp. I used Perspex for the windows & PVC tube for the wall. It has a filler hole & plug.

This has worked out fine, thanks Reed.

 

So I can present, The Lamp, The Cell, The Spectra.

The Lamp, 24 watt Mercury HID Flashlight.

The Cell, is 40mm thick & made to fit the head of the lamp, approx 70mm dia.

The Spectra, was taken with an Amici Prism Spectroscope. The spectrum is logarithmic, not linear, the UV end is more spread out than the IR end which is compressed. That is why I like to use this spectroscope for UV work. The first line on the left is 365nm to about 610nm, for this lamp. This will be now very useful for the 400 watt HID as it only passes UV & IR, no Visible, so it will be a true Short Wave UV lamp.

 

The Lamp, 24 watt HID, behind on the right is the 400 watt HID.

post-31-0-15025200-1413965217.jpg

 

The Cell, 40mm thick cell of 12.5% (1/8) Copper Sulphate solution.

post-31-0-95267500-1413965250.jpg

 

The Spectra, the spectrum of the 24 watt HID flashlight, with the 40mm tank of copper sulphate.

365nm to approx 610nm.

post-31-0-99253600-1413965267.jpg

 

The Spectrum of the full HID, no filters. 365nm to over 850nm.

post-31-0-41971000-1413965283.jpg

 

This has been a successful & interesting project & I will now go ahead & make another larger (300mm x 300mm x 50mm) tank for 400 Watt UV Party Lamp :D

 

Cheers

Col

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Yes, thanks John, I will do some more testing before I finally make the tank.

The lamp wouldn't be on for a long time, only on for long enough to get a few shots or so, 5 to 10 minutes.

There will be approximately 4.5 litres of water in the tank, so the rise in temperature should be slow. It takes 100 degrees C to deform Perspex, I am not sure that any surface will get that hot ?? I am more worried that a glass tank will not take the rise in temperature & will crack or shatter ??

Cheers

Col

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Ah, I see in your photo you have an HID Blacklight.

The black glass envelope of that lamp already filters out a great deal of the Vis/NIR.

 

I have measured several of the larger HID's but not that one.

Here is a crude emission spectrum from a supplier website:

 

post-24-0-16344300-1414006482.jpg

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Thanks very much John, I haven't seen this chart before.

I have taken an Amici Prism Spectrograph of the 400 watt HID UV Party lamp.

This is how my full spectrum Sigma DP2 camera sees it.

 

Amici Prism Spectrograph of the 400 watt HID UV Party lamp.

post-31-0-57224900-1414019525.jpg

 

Cheers

Col

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Fantastic Idea with the "liquid filter" Colin!

 

I took some Pics with the Sigma SD10. I removed the hotmirror filter and noticed there was much ir in the light of my HID Party lamp.

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  • 1 month later...

Just an update on how / where this is all going.........

I have purchased a Chinese 75watt Mercury HID lamp & integral ballast on eBay.... http://www.ebay.com....984.m1497.l2649

I can use this lamp with the head & reflector of the 24w HID lamp above & other metal reflectors I have.

These lamps can be powered by a 12v gel battery, with the leads soldered to the terminals.

I was hoping to use this 75w HID lamp with a Blak-Ray's lamp filter, but the one I purchased, cheap & the self-ballasted one, seems to be an older model & the filter leaks heaps of IR & not much / any 365nm UV.

Long story - short.....

I tried the Schott UG11, with the 75w HID & killed the UG11 !!

It passed out trying to absorb all the IR & fractured into shards after a couple of minutes :)

It burnt my fingers too.........

Still on the long story - short......

I have been testing an idea of putting the UG11 inside the copper sulphate cell............

While I wait for a replacement UG11 to arrive, I have placed another similar filter (which I have also fractured some of these before, from too much absorbed heat, in front of the 24w HID lamp) inside the copper sulphate cell, & for the five to ten minutes I had it in front of the 75w HID, it has survived, with no noticeable rise in temperature of the copper sulphate solution :P

So I will wait for the battery to recharge & run it all again & test the copper sulphate solutions temperature & see how things progress.

Cheers

Col

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That test went marvelously well. I ran the 75w HID lamp with the copper sulphate solution cell, with the 'woods glass' filter inside it, for 30 minutes with no damage.

The cell only warmed up to about 10 degrees above ambient. The lamp head was too hot to touch & the ballast was not much cooler.

Cheers

Col

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