Re: Wavelength for all Alt. Processes ?

Terry Glass

Should be 385-400nm!

All the Best,
Terry Glass

On Sep 7, 2021, at 6:23 PM, Terry Glass via <terrygla@...> wrote:

Would these units work for UV exposure? They are rated 390-400nm

All the Best,
Terry Glass

On Sep 7, 2021, at 4:01 AM, Scott Davis via <Scotttdavis@...> wrote:

I went with blacklight LEDs in my revamped exposure unit. They’re in the 380-390 range. I went a little overkill but I wanted to ensure even coverage for the largest possible prints I could make- I can go up to 16x20. So I have 16 strips of 22” length. My exposure times are 2 minutes now, down from 12+ with fluorescent bulbs, and more consistent. I’m printing palladium mostly at this point, with the odd cyanotype thrown in. Will be doing gum over pt/pd in the near future. 

On Sep 6, 2021, at 9:13 AM, Frank Gorga <fgorga@...> wrote:

My experience...

Processes that use the photo reduction of iron(III) to iron(II) are broadly sensitive to light at around 390 nm. Thus they work just fine with inexpensive BLB bulbs/LEDs. These sources also seem to work well for salted-paper. 

Photopolymer gravure does not work with the BLB sources, as it requires the shorter wavelengths of the more expensive 360 nm sources. I have no information on how the 360 nm sources work with the iron based processes, but they do seem to work for salted-paper. 

These days I use a simple plywood box with four strips of inexpensive,  pre-wired BLB LED strips which gives me 10 or 15 min exposure times for cyanotype and salted-paper. 

The nice thing about BLB LEDs is you don't need to really worry about managing the waste heat. My box has a few vent holes leftover from when it had fluorescent bulbs but no fan. It barely gets above ambient temperature by 15 min.

--- Frank 

On Sun, Sep 5, 2021, 3:13 PM Michael <pixelwaster@...> wrote:
I used to have a nice list of what range of light worked with what process.  I suspect it is on the drive that died.

I am looking to make a new one because I've seen youtubers use everything from 360nm (monochromatic)  to white light from a 500 watt tungsten spot. they all have short (<15 min) exposure times. I just would like to make an exposure box with the right light to start with.

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