I don't know. So far, with the machine, I'm getting cyanotype prints in 5-7 min equivalent to what I was getting in 3-4 min in full sun (early afternoon, December, Northern California.)
Is the UV light in the tanning machine good enough for Pt/Pd too?
I only have a low-end 4-color inkjet and it doesn't put down a very dense coat of ink on transparencies. I've made some nice prints by printing two copies of the negative and taping them together for more density. The printer does pretty well on paper, so I may experiment with waxed paper negatives. I'd love any advice or guidance.
Adam
I've read somewhere that yellow ink is a strong UV blocker. You could increase contrast by adding yellow to the shadows (after inverting). To be clear, I'm suggesting a) start with a B/W image, b) change mode to RGB, c) invert the image to a negative, and d) add yellow to the SHADOWS (which are inverted highlights). This makes the denser parts of the negative even less permeable to UV light, increasing contrast. One easy way to do this in Photoshop is with Image > Adjustments > Color Balance:
Tom
Or you just buy a second hand facial tanning machine (don't know what these are called inn english??) for $10 and make a small wooden box to carry it - with the bulbs facing down. These machines come in several sizes.
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I picked up one of these for 15 Euro. Found it just in time as well as I priced all the components and was well over 100 Euro. I will try this out. -Doug
Hi, Adam:The facial tanning unit arrived, cosmetically challenged but working just fine. I did a couple of tests using a cardboard box and built the unit below out of a couple of wine boxes a colleague rescued from the sidewalk and some scraps from the garage. Some sawing, drilling, nailing, screwing, and gluing, and voila!
I did a few prints this morning. I'm getting times of 5:30 to 7 minutes at a distance of about six inches--very nice!. Coverage is pretty uniform so far.
Now I gotta nail down the negatives. I only have a low-end 4-color inkjet and it doesn't put down a very dense coat of ink on transparencies. I've made some nice prints by printing two copies of the negative and taping them together for more density. The printer does pretty well on paper, so I may experiment with waxed paper negatives. I'd love any advice or guidance.
Adam
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Hi, Adam:
Would you share the make/model of this tanning unit that you used to make your exposure box. I keep blowing these CFL lamps on my unit (may be my wiring is not upto par.) I am thinking of making an another one like yours rather than keep buying new bulbs. Also what the largest size you are able to do with this box.
Thanks.
P.S. For negatives, try using colorized ones to add to the opacity. Greenish inks are more opaque to UV light than black ink. The exact RGB combo should be based on experimenting with your particular set of variables (UV source, chemistry and the type of inks.) But you will be surprised to find that the densest color is far from the R/G/B of 0/0/0
Adam:Hi Niranjan,
The brand of the unit I bought is Bion. I got it used on eBay. It has 4 8w tubes. From pictures I've seen online, this unit is sold under many brand names (CalSun is a common one in the US, Phillips in Europe). I get good even coverage on 9x12 inch paper at a distance of about 6 inches (using negatives that are 81/2 x 11) in about 6 min. I could probably get even coverage with negs of 11x14 inch at a greater distance, but with (much?) longer exposure times. I paid US$75 and I'm happy with it so far.
As to the negatives, I'm getting pretty good results with my method of two negatives together using black ink. Other methods might be better, but I'm not eager to start the process of trial and error all over again.
Keep us posted on your progress,
Adam
I worried about the same before building mine (12x16 box with 18 bulbs) but from my tests on a 11x14 frame I found very little spatial variation. I have not used it for cyanotypes or for any of the other processes mentioned - so far only for Centennial POP and a little bit of salt prints. The typical exposures have been 20-25 minutes to achieve the Dmax. It does get hot like hell, probably putting that many bulbs in the small space was an overkill. Might need an exhaust fan if I ever want to do more than a couple exposures in a day. If I ever built a bigger one, I would look into building with LED's like this one that presumably should be cooler than CFL's:
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The biggest problem still is that strip LEDs don't emit the correct wavelength for cyanotype.Thanks for sharing this but a few things I would point out. UV LEDS do create heat and need adequate ventilation. The ones you get from ebay or amazon are not really good enough. The main difference I have learned is that good LED strips contain a lot more copper to help with dissipating heat and usually start at $100 per roll of 16 feet. The cheap one on ebay don't have much copper and change intensity over 6 months. I used to be able to do exposures in 6 minutes for platinum and now it takes 30 minutes. The other problem is the silicone waterproofing turns yellow over time so get it with no waterproofing. I will be updating that page to a new one with better parts and ventilation.
Greg Brophy
Thanks for sharing this but a few things I would point out. UV LEDS do create heat and need adequate ventilation. The ones you get from ebay or amazon are not really good enough. The main difference I have learned is that good LED strips contain a lot more copper to help with dissipating heat and usually start at $100 per roll of 16 feet. The cheap one on ebay don't have much copper and change intensity over 6 months. I used to be able to do exposures in 6 minutes for platinum and now it takes 30 minutes. The other problem is the silicone waterproofing turns yellow over time so get it with no waterproofing. I will be updating that page to a new one with better parts and ventilation.
Greg Brophy
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