JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 No. Only why do we have to bear it in mind. the reflected light will be a lot less intense by the time it reaches the violin. Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 21, 2015 Report Share Posted July 21, 2015 the reflected light will be a lot less intense by the time it reaches the violin. Why ? Does it get tired ? ( just pulling your leg ...) Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 Why ? Does it get tired ? ( just pulling your leg ...) absolutely knackered, mate. Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 21, 2015 Report Share Posted July 21, 2015 the reflected light will be a lot less intense by the time it reaches the violin. No. All the light produced is inside the ( reflecting ) trash can. It goes nowhere. The photons will bounce around until adsorbed by the varnish curing process. Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 No. All the light produced is inside the ( reflecting ) trash can. It goes nowhere. The photons will bounce around until adsorbed by the varnish curing process. So none of it absorbed by the bloody big thing hanging in the middle of the box then? Quote Link to comment Share on other sites More sharing options...
pbelin Posted July 21, 2015 Report Share Posted July 21, 2015 And if you take the violin out and turn the light off, they keep bouncing forever Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 And if you take the violin out and turn the light off, they keep bouncing forever No, only as long as you don't open the door to peek..... Quote Link to comment Share on other sites More sharing options...
dan_s 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. No. All the light produced is inside the ( reflecting ) trash can. It goes nowhere. The photons will bounce around until adsorbed by the varnish curing process. So none of it absorbed by the bloody big thing hanging in the middle of the box then? It's good to quit as long as you appear distracted and not incompetent. The inverse square law has nothing to do with the situation here. BECAUSE OF THE REFLECTIONS. Quote Link to comment Share on other sites More sharing options...
JohnCockburn Posted July 21, 2015 Report Share Posted July 21, 2015 I'm sure you're right. It was just a throwaway remark based on the (presumably) fairly spherically symmetric/point source nature of these little SMD LEDs. Quote Link to comment Share on other sites More sharing options...
yancypup Posted July 22, 2015 Report Share Posted July 22, 2015 I think Carl is mostly right. Some light will escape, some will be adsorbed into the aluminum coating, some by the violin (which is the whole purpose) but most is reflected. With that many point light sources and the reflections, the coverage would be great! Quote Link to comment Share on other sites More sharing options...
l33tplaya Posted July 22, 2015 Report Share Posted July 22, 2015 It's good to quit as long as you appear distracted and not incompetent. The inverse square law has nothing to do with the situation here. BECAUSE OF THE REFLECTIONS. Metal trashcans do not have perfectly reflective surfaces. As a matter of fact, such a surface doesn't exist. In any case, I would be surprised, if over all of the trashcan surface, averaged, you obtained more than 40% reflection of initial energy, and probably much less. Subsequent reflections, after the first time, would be 30% of that, and so on. No counting what hits the varnish first, which would have even less reflection. As I reflect on this project, it would be good to fit a safety interlock, so removing the trashcan cover turns off the lights. No peeking. Quote Link to comment Share on other sites More sharing options...
Violadamore Posted July 22, 2015 Report Share Posted July 22, 2015 No, only as long as you don't open the door to peek..... Yeah, and if you do, your cat might die. Mine's currently entangled (with a ball of yarn) and I'd hate to have to do the math. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 22, 2015 Report Share Posted July 22, 2015 Metal trashcans do not have perfectly reflective surfaces. As a matter of fact, such a surface doesn't exist. In any case, I would be surprised, if over all of the trashcan surface, averaged, you obtained more than 40% reflection of initial energy, and probably much less. Subsequent reflections, after the first time, would be 30% of that, and so on. No counting what hits the varnish first, which would have even less reflection. As I reflect on this project, it would be good to fit a safety interlock, so removing the trashcan cover turns off the lights. No peeking. The trash cans worked in Robson's varnish workshops. Not as efficient as aluminum foil lined cabinet. And I peeked wearing glasses. Here's a photo from 2013. The cans had 4 fluorescent lamps each. Can anyone identify the smiling guy? Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 22, 2015 Author Report Share Posted July 22, 2015 Well, I got the LED strip today. It lit up but I heard a crackling sound from the transformator and it began to smell burnt so I don't dare to use it. Seems like you get what you pay for... I think I will order a better transformator before I can do some testing. Quote Link to comment Share on other sites More sharing options...
Michael.N. Posted July 22, 2015 Report Share Posted July 22, 2015 Yes. Be careful with some of those cheap adapters. Some can get a little too hot. Quote Link to comment Share on other sites More sharing options...
yancypup Posted July 23, 2015 Report Share Posted July 23, 2015 I've been trying to do some research on the net about frequencies of uv required for drying to no avail. It seems the optimum frequency is dependent on the varnish you are using. They make special varnishs for a variety of things (even nail polish) and the lamps they sell are for that specific product. I did find, as you might expect, that led uv lights are very narrow in their frequency band when compared to other uv light sources. I'm surprised they aren't monochromatic. So I guess the only way to tell if these would work is to try them. I get a little worried that direct exposure to the sun at this time of year along with the high temperatures could cause the varnish to bubble. So far I've been lucky. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 23, 2015 Report Share Posted July 23, 2015 Yancy, Do a search here on MN where we had a discussion on this. I think we concluded to use UV-A or UV-B, but avoid UV-C because of harmful eye effects. You can google for the spectral ranges of these different lamps. Quote Link to comment Share on other sites More sharing options...
yancypup Posted July 23, 2015 Report Share Posted July 23, 2015 I did read that but those are bandwidths. I wanted to know of the specific wavelengths of those uv leds would work. They are in the UVA band but at the upper end of it. And VERY narrow. Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 23, 2015 Report Share Posted July 23, 2015 I've been trying to do some research on the net about frequencies of uv required for drying to no avail. Just a suggestion : try UV specs for printing varnishes. Basically any will do, the shorter wave lengths will be faster but with less penetration. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 23, 2015 Report Share Posted July 23, 2015 Contact the manufacturer, or just try googling "UV LED spectral response curves". You are going to have to sweat some equity here. My bet is that the UV LED's will dry varnish quite nicely. There is no compelling reason for me to switch because my uv cabinet works. Mike Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 23, 2015 Author Report Share Posted July 23, 2015 Found a nice e-book about UV LED technology and curing applications http://www.radtech.org/uvledbook/ Quote Link to comment Share on other sites More sharing options...
yancypup Posted July 24, 2015 Report Share Posted July 24, 2015 Thank you Michael for the excellent recommendation. And thank you Fjodor, I just downloaded the ebook and skimmed it briefly. It appears UV leds can be made to produce just about any wavelength. And one chapter talks about developing a broad bandwidth uv led in the future. I'll take you up on your bet that it will work Michael and order a strip as soon as finances permit. I don't see why leds couldn't be used in conjunction with my fluorescents to make my light box "more better". Quote Link to comment Share on other sites More sharing options...
Fjodor Posted July 28, 2015 Author Report Share Posted July 28, 2015 I got the new power adapter and have now done a quick test with the cheap Chinese LED strip. I put the varnish on a piece of rib ca 10 cm from the strip. There were several LEDs pointing directly at each sample. 1. Homemade mastic linseed oil varnish 2. Old Wood Brescia Brown varnish 3. Joe Robson Greek Pitch Brown varnish Conclusion after about 12 hours: It seems to dry all varnishes but rather slowly. (I left a comparison strip in a dark place) There was still some very slight tackiness on all samples. The homemade varnish was most tacky, but this was expected because it has been most slow to dry. The strip warmed up but did not get very hot. I would compare the results to what I get with about 2 hours exposure to the facial tanning solariums I normally use. So the LED strips might be useful if you are not in a hurry or on a budget. I think I would leave it at least 24 hours to dry per varnish coat. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted July 28, 2015 Report Share Posted July 28, 2015 Thanks, Fjodor. Quote Link to comment Share on other sites More sharing options...
Carl Stross Posted July 28, 2015 Report Share Posted July 28, 2015 I got the new power adapter and have now done a quick test with the cheap Chinese LED strip. I put the varnish on a piece of rib ca 10 cm from the strip. There were several LEDs pointing directly at each sample. 1. Homemade mastic linseed oil varnish 2. Old Wood Brescia Brown varnish 3. Joe Robson Greek Pitch Brown varnish Conclusion after about 12 hours: It seems to dry all varnishes but rather slowly. (I left a comparison strip in a dark place) There was still some very slight tackiness on all samples. The homemade varnish was most tacky, but this was expected because it has been most slow to dry. The strip warmed up but did not get very hot. I would compare the results to what I get with about 2 hours exposure to the facial tanning solariums I normally use. So the LED strips might be useful if you are not in a hurry or on a budget. I think I would leave it at least 24 hours to dry per varnish coat. IMG_20150727_211128~2.jpgIMG_20150727_213224.jpg IMG_20150727_213254.jpg Very neat ! I place my LED much closer to the varnish sample and it dries them within an hour or two. But my LED gets very hot. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.