Blacklight for pringting?

ChristopherCoy

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On a whim, I googled DIY plans for a platinum UV box. I was surprised to see that this guy built it with run of the mill UV-A black light bulbs. I mean, are these the same black light's you can get at any Spencer gifts in the back of the store near the incense, sex toys, and lube? Right over there by the lava lamps?

For some reason I thought that alternative processes need UV lights like those of a tanning bed. The ones that make you smell crispy, but not over fried?

If this is the case, I'mma have to build me one of these sooner than I thought.
 

koraks

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Yeah, I use a bank of blb tubes. Works a treat, relatively easy to put together, parts were easy to get, cost effective.

Forget about the little screw in bulbs, cfl's or les bulbs though. Way too little power. You want a couple of hundred watts worth of power.
 

fgorga

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I just refitted my homemade exposure unit with blacklight LEDs.

My unit used to have six fluorescent tubes (the exact type eludes me)... they were old (probably 15 years) and balky (slow to turn on completely). I replaced the fluorescent fixtures with these: https://www.amazon.com/gp/product/B071NT6189/

I have only been using the LEDs for about two weeks and only for cyanotypes (thus far) but things are working well.

Exposure times are about 5 min... less than half what they were previously.

The unit (with no fan) runs much cooler than before.
 
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ChristopherCoy

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fgorga said:
I just refitted my homemade exposure unit with blacklight LEDs.
Click to expand...

I saw a video where a guy made his box with these. I believe he was in the UK. If these work, they would be my preferred light source.

But since I don't know much about it yet, I wonder if there would be "hot spots" on the final images.

ETA: I guess I should have looked at your link. In the video I'm referring to the guy used these.
https://www.ebay.com/itm/2PCS-UV-Li...905291?hash=item56d2ce080b:g:tGIAAOSwcB1eEyT6
 

Donald Qualls

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koraks said:
Forget about the little screw in bulbs
Click to expand...

Depends on what process and how large you're printing. I've printed salt prints and cyanotype with a single CFL spiral black light bulb in a clamp-on reflector lamp, around a foot from a 5x7 printing frame, and had good results. I wasn't in a hurry, was exposing by eye, and the alternative was to wait for sunny weather.
 

Vaughn

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If one is buying just the blacklight tubes...the BLs are cheaper and maybe even a little faster than the BLBs -- BLs do not have the internal filter for white light.
 

fgorga

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I haven't noticed any hot spots, but most of my testing since the refit has been with 4x5 negatives.

The inside of my box is painted white so that may help. I would switch to a crinkled aluminum foil lining if I find problems when I move to larger sizes.

When I had 24" fluorescent bulbs in the unit, I never had trouble with 11x14 negatives. I never tried larger than that.

I took a look at the article you linked to. I think that this information is a bit dated now that LEDs are common.
 

koraks

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Donald Qualls said:
Depends on what process and how large you're printing. I've printed salt prints and cyanotype with a single CFL spiral black light bulb in a clamp-on reflector lamp, around a foot from a 5x7 printing frame, and had good results.
Click to expand...
If one has ample time & patience, then yes. I'm always short on the latter. A single 50W BL CFL will probably take about 1-2 hours at the very least to properly expose a salt print. At roughly 1kW/m2 my light source takes between 10-15 minutes to do the job, depending on the negative. Then again, the major improvement in my salt prints was when I figured out that most of the examples I saw online and my earlier prints were all underexposed by 1-2 stops to accommodate way too thin negatives.
 

Vaughn

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There is something about a beefy negative and alt. processes that go together so nicely...gives the chemical action of light (as they use to say) time to do its thing (especially processes that have a partial printing-out image such as Platinum).
 

Donald Qualls

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Yep, you need enough density to preserve the highlights while you expose enough to bring up the shadows. And that, River City, means Contrast with a capital "C"!
 

Vaughn

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Donald Qualls said:
Yep, you need enough density to preserve the highlights while you expose enough to bring up the shadows. And that, River City, means Contrast with a capital "C"!
Click to expand...
You will have to pry the last 8x10 sheets of Kodak Copy Film from my dead hands -- even with the base fog!
But I did just get 100 sheets of 8x10 Tech Pan!!!!
 
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ChristopherCoy

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Vaughn said:
You will have to pry the last 8x10 sheets of Kodak Copy Film from my dead hands -- even with the base fog!
But I did just get 100 sheets of 8x10 Tech Pan!!!!
Click to expand...

Why don't you SHOOT it before we HAVE to pry them from your cold dead hands? You can't take them with you when you go!
 

Vaughn

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It is my specialty film for scenes of low SBR which allows me to produce negatives with excellent tonal qualities up to a DR of approaching 3.0. Otherwise I use FP4+. The Tech Pan will be used along with the Kodak Copy Film for the same purpose...boost contrast. I have used it in 4x5 in the redwoods before.

The below scene read on my Pentax Digital Spot meter a range of 9 to 12. Rating the film at ASA 25, I exposed at 10; F64 for 20 seconds. The film has no reciprocity failure as far as I can tell, but I was hoping for some but did not end up needing it. Exposure controls the contrast for this film, and my robust exposure plus ample development got me the contrast I need. Carbon print. There is actually a lot of glare off the print when I tried to photograph it, but you'll get the idea.

Edited to add -- For exposures, I use a self-ballsted 750W Merc Vapor bulb.
 

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