UV LEDs for curing varnish?

[Michael Doran]

I was intrigued by the idea, so I called my UV lamp supplier. (Currently I'm using a mix of UVC and UVB fluorescent lights for tanning and UVB for drying varnish.)

He and I had a great conversation about LEDs in general as well as UV LEDs. The tests he's done showed that that the LEDs on the market today are not actually emitting very much UV, nor was he convinced that the proposed nanometer ranges are necessarily accurate.

He also told me that, in general, for a comparable amount of light emission (lumens) LED and fluorescent are about neck and neck in terms of energy efficiency. A particular LED or fluorescent tube could be slightly more efficient than the other, but he said it's mostly a wash. To be clear, both are drastically more efficient than incandescent. He thought the real draw to LED is the longevity, not the efficiency.

He said that to try and rig up a comparable set up to what I have in my light box with LED would be very expensive, about as efficient, and not emit nearly as much UV.

M

[pbelin]

Thank you!

[Fjodor]

I thought 10 cm would be a comparable distance to what would be the case with a violin in a small drying box.

Interesting, Michael. In the book linked to earlier, there were some discussion about LED intensity for different wavelengths. I understood that the technology is not there yet to produce equally intense LEDs within the shorter wavelengths (UVB , UVC)

[Fjodor]

BTW, my eBay account was suspended, out of the blue, a couple of days ago. I have no clue why and have not got a decent answer from eBay.

I have mostly ordered wood, tools, some chemicals, and most recently this UV strip. I read about another guy who had ordered some hunting gear and infrared binoculars, who was suspended appearantly without reason.

Maybe eBay has some overzealous algorithm that picks out "terrorists"

I don't know if this is the case but I thought I'd warn if some other are planning to order UV gear on eBay.

[Michael_Molnar]

I was intrigued by the idea, so I called my UV lamp supplier. (Currently I'm using a mix of UVC and UVB fluorescent lights for tanning and UVB for drying varnish.)

He and I had a great conversation about LEDs in general as well as UV LEDs. The tests he's done showed that that the LEDs on the market today are not actually emitting very much UV, nor was he convinced that the proposed nanometer ranges are necessarily accurate.

He also told me that, in general, for a comparable amount of light emission (lumens) LED and fluorescent are about neck and neck in terms of energy efficiency. A particular LED or fluorescent tube could be slightly more efficient than the other, but he said it's mostly a wash. To be clear, both are drastically more efficient than incandescent. He thought the real draw to LED is the longevity, not the efficiency.

He said that to try and rig up a comparable set up to what I have in my light box with LED would be very expensive, about as efficient, and not emit nearly as much UV.

M

Great information. Thanks.

[kwebb]

I was intrigued by the idea, so I called my UV lamp supplier. (Currently I'm using a mix of UVC and UVB fluorescent lights for tanning and UVB for drying varnish.)

He and I had a great conversation about LEDs in general as well as UV LEDs. The tests he's done showed that that the LEDs on the market today are not actually emitting very much UV, nor was he convinced that the proposed nanometer ranges are necessarily accurate.

He also told me that, in general, for a comparable amount of light emission (lumens) LED and fluorescent are about neck and neck in terms of energy efficiency. A particular LED or fluorescent tube could be slightly more efficient than the other, but he said it's mostly a wash. To be clear, both are drastically more efficient than incandescent. He thought the real draw to LED is the longevity, not the efficiency.

He said that to try and rig up a comparable set up to what I have in my light box with LED would be very expensive, about as efficient, and not emit nearly as much UV.

M

 

Michael, would you mind linking me to your supplier? I am having trouble finding the bulbs I need for a new light box. 

[Michael Doran]

Michael, would you mind linking me to your supplier? I am having trouble finding the bulbs I need for a new light box.

Sure! I'm happy to recommend them. The company is called Kelsun Distributors. Here's their website- www.kelsun.com

I'm fortunate that they are located nearby, but I'm sure they would ship to you if you're not local. They are familiar with violinmakers tanning wood and curing varnish with UV. The fluorescent lamps I buy are medical grade. The government requires that you sign a form saying that you're not going to use the UV lamps on people, and Kelsun got audited or something last year- so they've been more strict about getting that documentation recently.

M

[JohnCockburn]

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.

yep. photons less tired.

[Carl Stross]

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.

 

 

yep. photons less tired.

 

Nope. This time is the "inverse square law". 

[Fjodor]

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

 

A small addition to the test. I have done a similar test with a SMD2835 LED strip with a peak wavelength at 365nm. These

LED strips are more expensive than the 395nm variety.

There was no noticable drying speed improvement in comparison with the SMD5050 395nm strip, so I would not not necessarily recommend them.

I plan to build a small drying cabinet with the two strips (total 600 LEDS). They are not the fastest but seems to work OK.

[Jan Jozef]

On 8/31/2016 at 12:38 PM, Fjodor said:

 

A small addition to the test. I have done a similar test with a SMD2835 LED strip with a peak wavelength at 365nm. These

LED strips are more expensive than the 395nm variety.

There was no noticable drying speed improvement in comparison with the SMD5050 395nm strip, so I would not not necessarily recommend them.

I plan to build a small drying cabinet with the two strips (total 600 LEDS). They are not the fastest but seems to work OK.

Thanks, Fjodor.

Could You share with us about the impressions and Your conclusions?

I know it is old thread:)

Best regards,

Jan

[Fjodor]

Hi Jan,

Here is a link to my bench tread where you can see how I did with the drying "box". I used two 5m led strips. It is not so fast as the solariums i used before but I can leave it overnight without worries.

 

[David Burgess]

1 hour ago, Fjodor said:

Hi Jan,

Here is a link to my bench tread where you can see how I did with the drying "box". I used two 5m led strips. It is not so fast as the solariums i used before but I can leave it overnight without worries.

 

What are your worries with leaving it overnight using fluorescent bulbs?

[Fjodor]

40 minutes ago, David Burgess said:

What are your worries with leaving it overnight using fluorescent bulbs?

Well, not precisely worries, more of a convenience for me. The set up I had earlier was a pair of small facial tanning solariums with 1 hour timers, which required me running to the workshop every hour and start them over.

[Gino Yu]

I'm using LED  for my varnish. I was living in China, So I can get a good price. I have tried many of them. 

They are quite different from fluorescent bulbs and also from each other. 

1.  The wattage doesn't indicate as much as fluorescent bulbs. What kind of lamp bead are they using is the most important thing.   The wattage might be the same but the price and the technology can be completely different.
2. The beam angle is much narrow.  If we can say the fluorescent bulbs are 360°, Then the LED's might be  45-60°, again depends on lamp bead. In this point of view, the  fluorescent bulbs with Aluminium foil can be much more efficient.
3. I have a little talk with the supplier, the LED UV need to be placed as close as possible to the object, Its efficiency diminishes rapidly with distance.

For my opinion, the LED strips you have very low energy, they are made just for decoration. Might do the work, but same wattage, the fluorescent bulbs can do a better job.

In my picture, The big black spot LED light I'm using, It's my finial choice. 10 watts, for normal oil-varnish not too thick, It can dry it in 1-2 ores. But, they are not cheap at all. In China, it cost me about 60 US dollars each. 

 

Good luck.