Fjodor Posted July 19, 2015 Report Share Posted July 19, 2015 Some years ago I asked about UV leds for curing varnish. I.e. making a drying box with leds instead of light bulbs. The opinion at the time was that they were not up to the task yet. Some days ago I stumbled upon a blog by Andrew Carruthers who has built an drying box with UV LEDS. http://www.andrewcarruthers.com/led-light-box/ He lists some PROS and CONS with his LED setup: LED Pros - low energy use and consequently… - temperature and humidity very close to ambient. This means less neck movement and popping seams - low running and maintenance cost. Longer bulb life without deteriorating performance over time. - Health: UVA spectrum is less damaging for eyes and skin, than the UVB spectrum fluorescent bulbs usually prefered by violin makers. Apart from taking the photo below (while wearing shades) I still treat the lights, which are very bright, as harmful, switching off before opening the cabin. - low profile, more robust bulbs give more working space – or smaller cabinet - low voltage feels safer LED Cons - Higher set up cost - UVA cures varnish less aggressively than UVB (This is off set by the greater light intensity from LEDs) and may not work with all varnishes - My UVA LED light box doesn’t tan wood as aggressively as the old UVB fluorescent light box. I ordered a set of cheaper UV LEDS from ebay for testing purposes. 5 meter 300 LED strip 5050 395-400nm spectra with a 12v 6A power source (ca 30 euro) and intend to test if it can dry oil varnish. I will report back. Does any one else has experience with UV LEDS? Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 19, 2015 Report Share Posted July 19, 2015 Does any one else has experience with UV LEDS? I do. Quote Link to comment Share on other sites More sharing options...
Dwight Brown Posted July 19, 2015 Report Share Posted July 19, 2015 http://www.intl-lighttech.com/products/light-sources/leds/uv-leds I found this. dlb Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 19, 2015 Author Report Share Posted July 19, 2015 Thanks for the link.By the way this is the set I orderedhttp://www.ebay.com/itm/5M-UV-Ultraviolet-395nm-5050-SMD-300-LD-Flex-Strip-Light-12V-Power-supply-/231575074039?pt=LH_DefaultDomain_0&var=&hash=item35eaf334f7 If it does nothing at least I have some cool christmas tree decorations Quote Link to comment Share on other sites More sharing options...
Dwight Brown Posted July 19, 2015 Report Share Posted July 19, 2015 I had never even thought of UV LEDs. There seems to be lots of them in UVA,UVB,and UVC. If you were here in with me in South Texas today I think you would be able to sun tan an instrument but you might have a hard time keeping it from bursting into flames!! We are well into real Del Rio Summer weather. Probably won't stop until November or so! dlb Quote Link to comment Share on other sites More sharing options...
Dwight Brown Posted July 19, 2015 Report Share Posted July 19, 2015 https://en.wikipedia.org/wiki/Ultraviolet#Subtypes This is a kinda good article and includes some stuff about leds dlb Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 19, 2015 Report Share Posted July 19, 2015 I had never even thought of UV LEDs. There seems to be lots of them in UVA,UVB,and UVC. They're used quite a bit, mostly for nail polish curing, dental stuff , glass repair resin curing etc. I use them for curing small varnish samples and they work nicely. They get HOT though. Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 19, 2015 Author Report Share Posted July 19, 2015 ThanksIf I understood correctly LEDs can only be produced with a narrow emitting spectra. 395nm would be at the end of the UVA spectra. Interestingly the leds Carruthers linked to were listed as around 440nm.Carl, what variety do you have? Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 19, 2015 Report Share Posted July 19, 2015 Thanks If I understood correctly LEDs can only be produced with a narrow emitting spectra. 395nm would be at the end of the UVA spectra. Interestingly the leds Carruthers linked to were listed as around 440nm. Carl, what variety do you have? I'll have to check - I know I got them from Mouser.... LZ1 Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 20, 2015 Report Share Posted July 20, 2015 We need some testing. I like the concept, but do they dry varnish? Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 20, 2015 Author Report Share Posted July 20, 2015 Yes, I intend to test it on some different varnishes. BTW the link in the first post was not working but should be fixed now. Quote Link to comment Share on other sites More sharing options...
Peter K-G Posted July 20, 2015 Report Share Posted July 20, 2015 Interesting! Let us know how it works, if you also could put some wood wedges in the box and weigh them before and after to see if it also dries wood. Quote Link to comment Share on other sites More sharing options...
pbelin Posted July 20, 2015 Report Share Posted July 20, 2015 I thought about trying them but I didn't have time for that yet, and my tubes are still ok. I wonder if it's a good idea to have one single frequency, I would think that a broader spectrum is better. Unless one knows exactly what frequency one needs for a particular varnish. And tanning the wood might require a different frequency... Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 20, 2015 Report Share Posted July 20, 2015 There is a threshold frequency (or wavelength) where tanning and varnish drying kick in. This is related to the "photoelectric effect". You can have all the light you want, but if the frequency does not have the right energy, nothing happens. Beyond this threshold the reactions take place. Albert Einstein received the Nobel Prize for his theory of the photoelectric effect - not for relativity theory. Quote Link to comment Share on other sites More sharing options...
Michael.N. Posted July 20, 2015 Report Share Posted July 20, 2015 I thought about trying them but I didn't have time for that yet, and my tubes are still ok. I wonder if it's a good idea to have one single frequency, I would think that a broader spectrum is better. Unless one knows exactly what frequency one needs for a particular varnish. And tanning the wood might require a different frequency... I've tried many different types of varnishes in my BL 350 UV box. It's dried them all. I have a Pine resin varnish that I made (burnt it!) that is touch dry in 4 to 5 hours. Very fast but that's probably because it was super heated. Typically a Pine resin varnish will take 7 to 8 hours to touch dry. It also tans wood. Perhaps not as fast as other wavelengths but then I wouldn't really know. I've just used the BL 350's. Quote Link to comment Share on other sites More sharing options...
Dwight Brown Posted July 20, 2015 Report Share Posted July 20, 2015 There is a threshold frequency (or wavelength) where tanning and varnish drying kick in. This is related to the "photoelectric effect". You can have all the light you want, but if the frequency does not have the right energy, nothing happens. Beyond this threshold the reactions take place. Albert Einstein received the Nobel Prize for his theory of the photoelectric effect - not for relativity theory. Michael, you are a man after my own heart! Not many people know about Einstein and the photoelectric effect. 1905 was a hell of a year! When ever anyone gets to big for their britches all you have to do is think of the myrical year papers, pretty good for a patent office clerk. I saw a video a while back that showed a glass plate from the Lick Observatory that was used to prove relativity, imagine the the real plate! I got to see the Zeiss blink comparator at the old Lowel observatory in Flagstaff that was used to find Pluto. I love that stuff. dlb Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 20, 2015 Report Share Posted July 20, 2015 Dwight, I shook hands with Clyde Tombaugh. Does that top you? Nevertheless, you visited Lowell. Wow! I did not. Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 20, 2015 Author Report Share Posted July 20, 2015 Interesting! Let us know how it works, if you also could put some wood wedges in the box and weigh them before and after to see if it also dries wood. Yep, I thought I try them on a small sample first before I build a box. If it works for curing I will make a box and try to leave some wood in for a longer time to see if it is any good for tanning, I could do some drying tests at the same time. Quote Link to comment Share on other sites More sharing options...
Dwight Brown Posted July 20, 2015 Report Share Posted July 20, 2015 Dwight, I shook hands with Clyde Tombaugh. Does that top you? Nevertheless, you visited Lowell. Wow! I did not. Yes, it sure does! Our 'Cello teacher at Interlochen was an amateur telescope maker. he gave me my appreciation for technology and fine mechanical things. He owned a 1703 Gofriller 'cello when I knew him. You could look at it for months. DLB The Discovery channel folks have built them a new observatory further outside of town with a big new telescope. The original observatory has Lowells grave site, and the Clark Refractor is still functional. They use it more for education and public viewing. Quote Link to comment Share on other sites More sharing options...
yancypup Posted July 20, 2015 Report Share Posted July 20, 2015 If these work for drying varnish, I'm in. You could line a metal trash can with a couple of these strands and get great light distribution IF they will dry varnish. Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 21, 2015 Author Report Share Posted July 21, 2015 If these work for drying varnish, I'm in. You could line a metal trash can with a couple of these strands and get great light distribution IF they will dry varnish. This is what I had in mind. You could tape the strip in a spiral inside a trash can for an easy installation. For a cello something bigger is requried of course. Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 If these work for drying varnish, I'm in. You could line a metal trash can with a couple of these strands and get great light distribution IF they will dry varnish. If you're relying on multiple reflections you have to bear in mind the old inverse square law. Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 21, 2015 Report Share Posted July 21, 2015 If you're relying on multiple reflections you have to bear in mind the old inverse square law. I don't get it. Could you explain ? Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 I don't get it. Could you explain ? Explain what? Inverse square law? Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 21, 2015 Report Share Posted July 21, 2015 Explain what? Inverse square law? No. Only why do we have to bear it in mind. Quote Link to comment Share on other sites More sharing options...
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