Underpowered UV exposure box?

[Ecoleica]

Hi all, I am fairly new to alternative printing and I have been wanting to get consistent results with my cyanotypes (soon to be salt prints). So i contacted a local screen printing company that makes their own uv exposure boxes and purchased one of their units. I have done a bit of experimenting with it and it seems woefully underpowered for digital negatives (one step print took around 2 hours to expose!). I have attached a photo of the box. Currently there are 6x T5 8W tubes. Now I can always add more T5 Tubes to the unit or I could start from scratch and build something bigger and more powerful myself. What are your thoughts?

 

[pschwart]

You can do a lot better than that box.

Build your own with at least 8 T8 BL bulbs.
Use electronic ballasts.
The bulbs are way too far apart in the unit you purchased.
Install a fan to keep the bulbs cool.
I think a pizza oven design (with a door) is safer and provides better cooling
18" BL bulbs can be had for about $4 each and they last for years.

 

[Doyle Thomas]

could be your chemistry too

 

[Ecoleica]

No issue with the chemistry that i know...I get good results when using the sun as a UV source

 

[Mainecoonmaniac]

Your box looks awfully deep. Maybe if you got the tubes closer to your print, it will speed things up. By lowering your tubes, you're taking advantage of Inverse Square Law.
re

 

[ced]

Are they wired correctly (may be reducing the output) are they all coming on as there are switches on each tube?
I would put more tubes, some kind of reflectors (hammered chrome/alu sheets or foil and get the lamps closer to your contact frame.

 

[adelorenzo]

Zombie thread guys

 

[ced]

Zombies rule the planet...

 

[Dahod]

As ced mentioned, you might want to check the wiring. From the picture it appears they're wired in series but every other unit I've seen and the one I built was wired in parallel See this article here ( http://web.physics.ucsb.edu/~lecturedemonstrations/Composer/Pages/64.36.html ) regarding wiring and bulb brightness.

I'm assuming they put in the correct UV bulbs for you so adding more would be a good thing. There's a lot of space between those T8 bulbs.

 

[MattKing]

Does anyone know whether the back panel might play a role?
With respect to visible light, a white background helps to reflect light forward. Is there a background that reflects UV?

 

[Mainecoonmaniac]

One question none of us asked what kind of tubes are they. I use actinic tubes made for aquariums and my exposure times are 7 mins.