Number of BL bulbs

I need to order bulbs for my the UV unit I am building. The problem is I don't know how many I will need.

I will not be printing bigger than 8x20.
Right now I will only be doing 8x10 and smaller.


If I leave finger space between the bulbs I am looking at 6x24 inch bulbs right?

MY fluorescent UV box has eight bulbs as close together as possible. The tombstones touch and thus limit getting any closer together. I would suggest a box containing 8 - 24" BL bulbs for the use you anticipate.

I've been able to do fine with six BLB bulbs. I believe the BLB bulbs have greater UV output, and so probably compensate for the reduced total wattage. I'm getting 6:00 - 6:30 printing times with this kit in spring through fall when the humidity is up over 50% in my house. When it drops in the winter, I get 10:00 print times. Not too bad.

mark said:

I need to order bulbs for my the UV unit I am building. The problem is I don't know how many I will need.

I will not be printing bigger than 8x20.
Right now I will only be doing 8x10 and smaller.


If I leave finger space between the bulbs I am looking at 6x24 inch bulbs right?

Click to expand...

All of the UV units that I have built using 24 inch tubes use 12 bulbs spaced one eighth of an inch or so apart (maybe a little more). Using 12 bulbs will give you very even uniform illumination without having to be concerned about exactly where your contact printing frame is placed inside the exposure unit. It also provides you with the space to use a vacuum easel, which I would reccomend for negatives of that size. I've built several of these units for others and I've never had a complaint about uneven illumination or difficulty of use.

donbga said:

All of the UV units that I have built using 24 inch tubes use 12 bulbs spaced one eighth of an inch or so apart (maybe a little more). Using 12 bulbs will give you very even uniform illumination without having to be concerned about exactly where your contact printing frame is placed inside the exposure unit. It also provides you with the space to use a vacuum easel, which I would reccomend for negatives of that size. I've built several of these units for others and I've never had a complaint about uneven illumination or difficulty of use.

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Exactly like the one I built Don, and as you said never worry about where the contact frame is inside the box as long as it is in the box.

Hmmmm...Twelve bulbs move out of my budget. I will have to give it some thought.

Flyingcamera, Jim
Do you have issues with uneven illumination, ever?

No, I have not had issues with even illumination, even when printing a 10x16 or 7x15 image on 12x20 paper. I made my unit with six BL-B fixtures from Home Depot - ballasts, power supplies, switches and bulbs included for about $17 per fixture. The bases of the fixtures are about 1 1/2" wide, so I measured off 2" from center of bulb to center of bulb on the board I mounted them on. I've had no problems with illumination, or with overheating using this scenario. My prints don't dry out or overcook during printing. My contact printing frame's glass is about 3" below the bulb surface.

I have almost the same setup as FlyingCamera (because I consulted him on making it). I started with 8 bulbs, as close together as possible, to allow for future larger prints. One of the units (these are ready-made units with bulb, ballast, switch, etc in one plastic unit) got disfigured...presumably by heat...and stopped working. It was dead in the center, so I removed it, pulled the end unit into the center, and now run with 7, as close together as the housings allow (about an inch gap between the actual bulbs?). These are about 4 inches above the contact frame. No scalloping or unevenness.

I am contemplating a NuArc 26-1K, though
Neal

Cool. thank you.

TheFlyingCamera said:

I believe the BLB bulbs have greater UV output....

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Might want to check this Scott. I think the BL's are actually better bulbs. Can't get those at Home Depot.

wilsonneal said:

I am contemplating a NuArc 26-1K

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Do it. You won't go back.

Bill

billschwab said:

Might want to check this Scott. I think the BL's are actually better bulbs. Can't get those at Home Depot.
Bill

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My understanding is that they are the same bulbs, but the BLB have a visible-light filter coating on the inside, thus cost more.

But I have been wrong before! Vaughn