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Need UV source
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PostPosted: Thu Jun 27, 2013 5:48 pm    Post subject: Need UV source Reply with quote

I'm about through with my fungus removal efforts on my Aero Ektar. It's time to attack the thorium yellowing of the rear element.

I had a plan: Expose rear element to the sun

A problem has arisen: We are receiving very little direct sunshine here where I live, and little is in the forecast

I live in the Northern Hemisphere. We are getting a LOT of daylight; just not much sunshine. It's cloudy.

I have struggled to think of a good UV emitter, an artificial source, I might already own. I've paged through my entire mental file but am coming up short.

I considered my carbon arc lamp and rejected long term use of that as impractical and, frankly, messy. Carbon arcs need ongoing gap readjustment and, besides, they emit a lot of RFI and visible light along with UV.

I thought of a heat lamp . . . but that's infrared, not UV.

I have my old photoflood reversal lamps from color film and print developing. They are incredibly bright and might emit a useful amount of UV. But they have very limited life and run circa 500 watts; probably not a good solution.

Some years back I owned a nice florescent UV tube. It was like a common florescent lamp, but without the phosphors. It glowed sort of purple and was dangerous to view with the naked eye. Sadly, I sold that unit to a fellow who wanted to use it to sterilize food. That sale was a mistake and I regret it.

So I need a cheap source of UV and I'm out of ideas. What easy options am I overlooking? With a lot of the fungus now removed, this lens element is looking more yellow than before. I need the strongest UV source I can afford. If I have to wait for sunshine, the way things are going, I might not be able to reassemble my lens for a year or two. Sad


PostPosted: Mon Jul 01, 2013 12:14 am    Post subject: Reply with quote

I am thinking along the same line. I don't know, but one of those false bills detector lamps (fraud detector lamp, says the box) might do the job, they are cheap and easily available (at least where I live).

Anyone with experience in the matter?


PostPosted: Mon Jul 01, 2013 8:51 am    Post subject: Reply with quote

You could try find an old solarium lamp?


PostPosted: Mon Jul 01, 2013 1:27 pm    Post subject: Reply with quote

All too weak. An old sun tanning quarz burner (HANOVIA for instance, see Click here to see on Ebay or Click here to see on Ebay ) would be best, as those emit tons of UV light, but are dangerous and need to be handled with care!!

Last edited by kds315* on Mon Jul 01, 2013 6:48 pm; edited 1 time in total


PostPosted: Mon Jul 01, 2013 2:30 pm    Post subject: Reply with quote

I'm grateful for all the thoughts and suggestions. Thanks.

Don't really have this solved, yet. The lens just sits. It's raining out.

Things will get better because (regarding this project) they cannot become much worse. I hope. Rolling Eyes


PostPosted: Mon Jul 01, 2013 2:38 pm    Post subject: Reply with quote

I have de-yellowed a couple of 1.4/50 and 2/35 takumar lenses with a 1000W UV lamp for tanning that my mother bought like 10 years ago and hasn't been used since a long time.
It is the most effective solution among the ones I tried - obviously except direct sunlight in summer.

Some white leds emit a certain quantity of UV light - the "famous" jansjo lamp from ikea appeared in a couple of articles on the web some years ago as a solution for yellowed lenses - but I found it to be extremely slow (if effective at all) in this process.


PostPosted: Thu Dec 19, 2013 6:20 pm    Post subject: Reply with quote

How about the water sterilizers used in fish aquariums? I have one for killing fungus in lenses that I'm going to try next week, might work for your yellowing condition too. Mine is a large 36 watt UV-C unit, and even if it takes longer than the Sun, it works when you want it to be on unlike the Sun for me at this time of year. CHeck ebay for replacement lamps and ballasts, or buy a complete water sterilizer unit and take the tubing part off and discard it.


PostPosted: Thu Dec 19, 2013 8:30 pm    Post subject: Reply with quote

UV lights are easy enough to find, there are bulbs that fit standard light sockets easily available. They are commonly used for aquariams, mainly with reptiles, and are very popular as disco lights. The next time you're hitting the dance floor just steal some blue bulbs. Laughing
In the UK Maplins usually stock them.

http://www.maplin.co.uk/c/gadgets-toys-and-hobbies/professional-light/uv-lighting



..


PostPosted: Sat Dec 21, 2013 3:42 am    Post subject: Reply with quote

The effects "black light" style produce very little of the UV that we need to kill off fungus or energize the yellow coatings, easy to get but a poor choice for the work at hand.


PostPosted: Sat Dec 21, 2013 8:37 am    Post subject: Reply with quote

Water sterilizers (low pressure Mercury tube) work at the 253.7nm Mercury line, which is the strongest emission line, but it is very dangerous, as it is pure UV-C.


UV-A sources, often based on high pressure mercury tubes, and blacklight tubes (that use a special UV-A emitting phosphor coating inside) etc are quite safe,
but indeed may have lesser impact.



Eye protection by spcialized UV suppressing glasses (>420nm) is a MUST! I burned my eyes myself working just with a UV power LED (365nm)!! Or even better,
put all into a light tight cabinet any only switch on when all is inside and safely locked!!


But if even a white LED lamp will cure (see OP above), then an UV-A source will do even better!


PostPosted: Mon Mar 06, 2017 8:23 pm    Post subject: Reply with quote

See my post here:

http://forum.mflenses.com/fast-lens-de-yellowing-without-a-uv-lamp-t68896.html


PostPosted: Tue Mar 07, 2017 12:28 am    Post subject: Re: Need UV source Reply with quote

guardian wrote:

Some years back I owned a nice florescent UV tube. It was like a common florescent lamp, but without the phosphors. It glowed sort of purple and was dangerous to view with the naked eye. Sadly, I sold that unit to a fellow who wanted to use it to sterilize food. That sale was a mistake and I regret it.

So I need a cheap source of UV and I'm out of ideas. What easy options am I overlooking? With a lot of the fungus now removed, this lens element is looking more yellow than before. I need the strongest UV source I can afford. If I have to wait for sunshine, the way things are going, I might not be able to reassemble my lens for a year or two. Sad

Any UV source that will harm fungus will be dangerous to the naked eye. There are 'black light' lamps readily available. (I brought an Edison screw type one for around £5 IIRC) They give out both UV & violet light, but I'm not sure if they are actually energetic enough to do much to fungus. More energetic sources such as mercury lamps & deuterium lamps are considerably more hazardous to use ( and far more expensive!)