BLB bulbs or 1000w bulb X-ray film carbon printing question

[Natenaaron]

I have a 1000w MH system I used to use with my classroom hydroponics garden, and I have the makings of an 8 bank BLB system just not sure which is the better avenue to set up as I take the leap into carbon using X-ray film.

I only have room for one system right now just not sure which I should go with. ANy help would be appreciated.

[koraks]

Personally, I would go for the fluorescents because they barely need time to heat up and they don't produce as much excess heat. Perhaps someone can chime in on the advantage of a spot light source in terms of contrast and detail, but I have found a bank of fluorescents adequate for my UV printing needs.

[Jim Noel]

I agree with Koraks about using the fluorescent, and there is the added advantage of their being slower, thus increasing contrast in the print.

[Jim Fitzgerald]

I have been using the NuArc 26 1ks 1,000 watt MH for carbon printing for years. The vacuum frame is a nice feature.

[Natenaaron]

Why are you using the MH bulb Jim? Is it because of the double emulsion?

[Jim Fitzgerald]

The mercury halide bulb is standard in the 1Ks. My negatives have a good density range and i always expose as deep as necessary into my thick tissue to get the most out of it as I can.

[sanking]

Both BL tubes and metal halide HID lamps can be used to expose carbon tissue. BL tubes are more efficient, produce less heat, and can be used with ordinary timers since they radiate near 100% as soon as they are turned on. Down side is that the diffuse light source will give soft results unless used with a vacuum frame.

HID lamps produce a lot more heat, and in timing must either be used with a light integrator, or left on for a couple of minutes to reach full radiation. However, being a near point-source light, they give very sharp results when placed about three feet from the printing frame.

Carbon tissue is fairly thick and needs a lot of pressure for good contact in printing, much more than silver gelatin papers or pt/pd. For best results a vacuum frame is needed with BL tubes, but a contact printing frame will give good results with HID lamps when positioned 2-3 feet from the printing frame.

BL tubes also give more contrast than HID lamps, other things being equal, but contrast can be adjusted with dichromate so this is a wash IMO.

Sandy

[koraks]

I might add that up to 8x10, sharpness is not a problem with a well-constructed non-vacuum contact printing frame. I constructed one with screws to apply the necessary pressure and it works like a charm. larger formats will be more of a challenge!

[Andrew O'Neill]

I have both. I prefer BLB. Exposures are a bit longer than my big old 1000W halogen vacuum table, and it stays cool. Xray films can make nice carbon prints.