[drut2007]

I have a freestanding light box that I am converting to an exposure unit. It will hold up to an 18" fixture. I have 4 new T8 18" fixtures to install in it. But I am have trouble finding a good bulb to use it. Most seem to be 15 watt. Is that enough watts? Any suggestions as to the exact bulb I should look for?
I am using Ulano QLT photopolymer emulsion. I have about a 4:30 exposure time with this in my other unit up north, but it has 6 bulbs that are 30" long. The bulbs seem to be anywhere from $7.00- $50.00. I don't want to buy the wrong ones, but the internet seems to give alot a different suggestions and some of them are not exactly what I am looking for. Please help...

 

[NoXid]

You want the unfiltered UV tubes. When turned off, those look sort of white, as opposed to the dark purple or black look of a "black light" tube. Prices for oddball stuff like this varies a lot between vendors, some charging much higher prices. Take your time searching.

Is the glass in your light box low iron? The more iron glass has, the greener it looks--most visible looking into the edge. Iron blocks UV, which is why windows serve as partial protection from UV light.

I had 4 * 40w tubes in mine and thought it underpowered ... but that was with T12 tubes which are not as efficient as T8, so hard to directly compare. The commercial units with T8 tubes seem to have around 7 tubes, so I would up your tube count.

 

[drut2007]

I am concerned about only having 4 bulbs that will most likely be 15-20 watt each. I looked at a $200 unit from ryonet that only has 2 25 watt bulbs in it and it had great reviews. I'm gonna try it with 4 and see. If not I will be able to add 2 more to it. As for the glass, I replaced it with a new piece of 1/2" plexiglass that my husband got from work. I have no idea if it will work or not, as I have not researched it yet. I know it will scratch easily so I will have to be very careful if it is useable. I do appreciate all the info, especially concerning the glass!

 

[NoXid]

I am concerned about only having 4 bulbs that will most likely be 15-20 watt each. I looked at a $200 unit from ryonet that only has 2 25 watt bulbs in it and it had great reviews. I'm gonna try it with 4 and see. If not I will be able to add 2 more to it. As for the glass, I replaced it with a new piece of 1/2" plexiglass that my husband got from work. I have no idea if it will work or not, as I have not researched it yet. I know it will scratch easily so I will have to be very careful if it is useable. I do appreciate all the info, especially concerning the glass!

It is my understanding that most acrylics (Plexi) block even more UV than regular glass, but there are some made to be more transmissive. I suppose you replaced the glass because it was originally white or frosted for the light box?

I doubt those Ryonet units with 2 UV twist CFLs could have an even enough light pattern ... seems someone on here had such an experience.

Anyway, build your unit and see what happens. See the link in my sig for info on how to determine the correct exposure time.

If the Plexi turns out to be a problem, you can order Low Iron glass online or through a local glass shop. The really pure stuff is extra expensive and sold under various brand names, but generic Low Iron glass gets you 80% there for 40% of the cost, and is what I used.

 

[drut2007]

Thank you for all your help!I was replacing the glass because the other seems so scuffed up. it actually had a separate sheet of plastic underneath the glass to filter the light.
I did not know that about plexi. it was free so I was hoping to get away with it, but instead it looks like I will be finding me some low iron glass instead. I did think the same about the ryonet unit not distributing the light evenly. Mine is only 20" x 18", that is why I am hope to get away with only 4 bulbs. They will be approx 2" below the glass. Hopefully that is ok