UV Source - Reflection Between Gaps

[Neil Poulsen]

This may be a nit, but I thought that I would ask.

I'm just finishing up my UV source for pt/pd printing. I've spent a lot of time on this thing, and if I do say so myself, it's a particle board masterpiece, one of my best.

I saw in a thread on this forum the advisability of installing sheet metal just above the UV lights. According to the thread, this helps to get the lights going, etc. I've done this. To my question, I'm wondering if I should paint this surface white? This surface is galvanized aluminum, and it's clear that there's a strong blue component to it's color. Being metal and reflective, especially of blue, I would think I'd be better off leaving it unpainted. It would seem this would do a better job reflecting UV light than white paint.

What do you think?

[Alex Hawley]

WOW Neil, you're the third person today that I've heard say is building a UV box. Add myself to the list. I haven't started building yet but have done a little research. My research indicates it does not make a difference. There is an article by Sandy King on Unblinking Eye that talks about UV light sources.

[David A. Goldfarb]

You can count me as number 4. Why now? Well, I want to print albumen, and I'm noticing that I have fewer hours of sun this time of year. I think we're all being driven by the seasons. In about six months, you'll see a bunch of folks from the southern hemisphere building UV boxes, and we'll be able to help them out, or maybe there are some people from the southern hemisphere who went through this six months ago and can give us some advice.

[Alex Hawley]

I think we're all being driven by the seasons. In about six months, you'll see a bunch of folks from the southern hemisphere building UV boxes, and we'll be able to help them out, or maybe there are some people from the southern hemisphere who went through this six months ago and can give us some advice.

Its not the seasons driving me David. It was Devil Kodak and the abrupt termination of the Azo supply. I thought I would be able to buy a thousand sheets of Azo this coming January but that's not going to happen now. So, I'm shifting to pt/pd.

[Kirk Keyes]

This surface is galvanized aluminum, and it's clear that there's a strong blue component to it's color. Being metal and reflective, especially of blue, I would think I'd be better off leaving it unpainted. It would seem this would do a better job reflecting UV light than white paint.

HI Neil - long time...

First - galvanized aluminum? I thought galvanizing was only done on ferrous metals. Are you sure you don't mean anodized aluminum?

Anyway - I'm not sure your question is one that can be answered without doing some testing as you would not want to paint your metal surface and then find out your paint absorbed a bunch of UV. Does your Gretag Spectrolineo go down far enough that you could test some paints and your sheet metal for reflectance?

If not, how about painting some posterboard and inserting it temporarily into your light box and then making a test print?

[sanking]

I was also confused by the concept of galvanized aluminium. Perhaps you meant galvanized steel?

If so, I am fairly certain that you would gain nothiong by painting the metal white. Even if you could paint it with something that would reflect a slightly higher percentage of the light the fact remains that 99% or more of the light that will reach the print will come from the tubes themselves, not from reflected light two or so inches above the tubes.

Several years ago we had a rather long discussion of this subject on the alt--photo list, which prompted me to actually tested various configurations with my bank of UV tubes, including painting the metal white, leaving it bare, and actually filling in the spaces between the tubes with crinkled aluminium foil. I was unable to detect any measurable difference between the different configurations.

Sandy

First - galvanized aluminum? I thought galvanizing was only done on ferrous metals. Are you sure you don't mean anodized aluminum?

[Dave Wooten]

the reflected light would be substantially weaker than the collective direct light from the tube...shouldnt make a difference IMHO

[Jan Pietrzak]

Ok, ok, ok

The sheet metal 'galvanized what-ever' is not needed. The metal part is to set up a 'ground field', so that the UV/FLs will light up.

Just ground all the ballasts to set up a 'ground field' each balast to the next and then to the wall socket ground. This will help make the UV/FLs come on.

Painting it mat or semi-mat helps keep the light even.

Some say that UV in not reflected 'I am not sure, Sandy how about you?

Building a box is very easy, just remember to ground the ballasts, keep the box on for the whole time, and work in a warm space UV/FLs work best above 65/70 degrees.

Jan Pietrzak.

[photomc]

may not be correct, but have heard the term "galvanized aluminum" for several years. Does not mean it is correct, but it is a common term...google it and you will find lots of threads. To the OP, do not know if it would make that much difference...I did paint the inside of my box (made for the plans on Edward Eng. Products website) there is so little space between the bulbs that I would not worry about it (mine has 12 blubs in a 22 inch wide box)

[Neil Poulsen]

I thought it was alumuminum, but could be mistaken.

To Jan:

I'm curious about your recommendation to keep the lights on all the time. Why should I do this? At Photographers' Forumulary, where I took Dan B's workshop on pt/pd and digital negatives, they had the units connected to a Gralab 300. I suspect your recommendation is to maintain better consistency, but thought that I would ask.

To All:

Has anyone tried using a compensating timer, either the now discontinued Zone VI or the Metrolux with UV sources? I'm wondering if that would help consistency? Do the sensors respond to UV light in the same predictable way that they respond to the fluorescent tubes used in cold light heads?

Probably the best is a single, high output, UV tube that's integrated over time.

Is the inconsistency going to be that bad, is it really an issue? Six minutes exposure to UV light is not subtle.