UV LEDs – Koraks tinkers

Wavy gravy – UV wavelengths for carbon DAS revisited

About this whole highlight business with DAS carbon transfer – it just never ends, does it? The last installment on this story had a loose end that I need to stitch up here. It’s about the nature of the light. Let’s have a look at how UV wavelength affects the curve, and highlight performance in particular.

Shine a little light – A brief note on UV output degradation in LED floodlights

I’ve been using cheap & cheerful UV floodlights to expose my alternative process prints for a little over a year now. Since then, a few people have remarked that there’s a problem with these LED flood lights: their power output reduces as the unit operates due to the LEDs heating up. How bad is the problem, really, and what to do about it?

Aching, flaking – A persistent problem with carbon DAS highlights

The problem that just won’t go away: disappearing highlights on DAS carbon prints. Twice so far I’ve declared this problem solved on my blog, only to have to revoke my ‘eureka’ shortly afterwards. Over the past few weeks, I’ve been systematically testing the process to find a cure. So far, to very little avail, I’m afraid. But perhaps that this writeup will (1) help me re-think the problem and (2) it’ll give some hints to anyone else struggling with DAS carbon problems by listing factors that can/should be evaluated.

Collimated vs. diffuse light – a cyanotype example

On a forum, someone asked how to get their cyanotypes made with 3D objects instead of a negative crisper. The fundamental issue at work here is how collimated or diffuse the light source is. Here’s a quick example of the difference between both.

Kind of blue – A test with UV LEDs for DAS carbon transfer

So the 400nm LEDs I had been using since October or so worked really nice for dichromate carbon transfer, but I ran into trouble with DAS carbon with them. Some further testing with my bank of trusted Philips BL tubes and a little theoretical exercise suggested that at least some 365nm exposure is needed to get DAS carbon to harden reliably especially in the highlights. So I’ve been testing a bit with 365nm LED options – two in particular that seemed attractive. This is a small report on these tests.

DAS right! – Solving the teething problems of DAS carbon transfer

Previously I wrote about trouble I was running into with DAS-incorporated carbon tissue. I just couldn’t get those tissues to transfer properly. Well, looks like I figured out why. In the process, I received some useful advice to boot, and perhaps there are some myths being established as well. Are you starting out with DAS and running into issues? Maybe some of the info in this blog can be of help.

Beam me down, Scotty: a new ultra-simple UV light source

It’s been a while since I wrote a somewhat acrid blog about the 300W UV floodlight unit I bought from AliExpress. The tone was acrid, because 300W in reality turns out to be about 75W. The conclusion was somewhat counter-intuitive, as I also mentioned that I found the unit so abysmal, I planned to buy some more of them. The reason is simple: while the unit doesn’t live up to its specifications, it still gives a lot of bang for your buck, and most importantly, it’s super easy to implement. Well, you be the judge of that!

UV tube vs led: a quick comparison

I already announced in my previous journal entry, but it arrived even quicker than I anticipated: the 300W UV led source I ordered from China. Although it was also laundry-and-house-cleaning day, I couldn’t resist giving it a go. And in particular, seeing how it would pitch against the bank of UV tubes I’ve had around for years. Here are my expectations when I ordered it: (1) higher total luminous flux, so shorter exposures, (2) better collimation, so less bleed and better detail rendering. How does it pan out, you think?