Screw-in UV Fluorescent source
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Ditto
I bought mine from a place called topbulb.com. They charged a lot for shipping, but otherwise I have no complaints.
Try Menards if you have one nearby.
Couple quick questions:
- I understand the use of black light UV bulbs. Do standard fluorescent put out enough UV to be useful? Or just stick with blacklights (or specially made UV fluorescent sources)?
- For the box, is the reflecting material important? I see some people use white. Does something like aluminum foil change UV reflectivity for better or worse?
- Do you just leave your light source "on" and slide a print under to keep things consistant? Or do y'all use "instant on" of the spirals and call it good?
- I understand the use of black light UV bulbs. Do standard fluorescent put out enough UV to be useful? Or just stick with blacklights (or specially made UV fluorescent sources)?
- For the box, is the reflecting material important? I see some people use white. Does something like aluminum foil change UV reflectivity for better or worse?
- Do you just leave your light source "on" and slide a print under to keep things consistant? Or do y'all use "instant on" of the spirals and call it good?
The BLB bulbs emit enough UV to be useful - but they are much slower than BL bulbs. Their lower price makes them worth using to me.
I did not see any significant difference between aluminum foil and glossy white paint. YMMV.
I use the instant on. In another thread, Sandy King actually tested and found light intenisty varaiation in the first minute (IIRC) but little after that. In a typical exposure running several minutes, the amount of variation was insignificant for our photographic purposes. I've come to the same conclusion in practice with both salt prints and VDB.
juan
I did not see any significant difference between aluminum foil and glossy white paint. YMMV.
I use the instant on. In another thread, Sandy King actually tested and found light intenisty varaiation in the first minute (IIRC) but little after that. In a typical exposure running several minutes, the amount of variation was insignificant for our photographic purposes. I've come to the same conclusion in practice with both salt prints and VDB.
juan
cperez said:
I was in a Pt/Pd workshop a couple of weeks ago with Tillman Crane. He recommends just leaving the box on throughout the printing session.
There are two reasons to want to NOT turn off the light source. With traditional fluorescent tubes with magnetic ballasts, there is a problem that some of the tubes may not start when they unit is turned on. Most box designs call for a metal plate that is supposed to correct this problem, but I don't think is an absolute guarantee. I know that Tillman has a problem with his boxes and has to tinker with them a bit to make sure that all of the tubes come on. And once they are on, you don't want to turn them off again.
CFL's (spirals) have a very pronounced warm-up characteristic, but traditional tubes also have this characteristic. Some months ago I found a report from a lighting technology research group at RPI in which they measured the warmup times - unfortunately, I failed to save it and now I can't find it again - but my recollection is that their conclusion was that while the warmup actually took 2-4 minutues, the light output was reasonably close to the maximum after the end of the first minute. With exposures of 4-12 minutes for various alternative processes, a variation during the first minute probably won't make a big difference. I believe that Sandy King did some tests that confirmed that conclusion. But again, just leaving them on avoids having to worry about warmup.
The other side of the coin is why would you want to turn them off between exposures. Fluorescent bulbs have a fairly long life expectancy, and their energy consumption is rather low. So economics are not a concern. I suspect that the two valid reasons have to do with the potential risks of leaving the UV source on continuously. One risk is that spillage from the lights could cause paper to be fogged before it is intentionally exposed - having a bare bulb left on continuously in the area where you are coating paper woudl be a bad idea. The other is that you want to minimize exposure of your eyes to UV - unless you like the idea of cataract surgery at an early age. Both issues can be addressed by have a UV box design with a door that can be opened only to insert and remove your printing frame, and left closed at all other times.
Monophoto said:
This makes a lot of sense to me for a workshop enviroment but in my own working conditions it would be a very big waste of energy to leave the tube bank on throughout a printing session. At 12 tubes X 40 watts each that turns out to be almost 500 watts, a fair amount of energy. And there really is no point in leavingthe tubes on all the time as far as exposure consistency is concerned, because tubes reach full output almost immediately on being turned on. Yes, turning them on and off will shorten the life of the tubes somwhat, but that is the only down side.
The spiral tubes put out a lot of UV light, especialy in the 27 watt size which is now available, but their major downside is that they do not reach full output until they have been on about a minute or so, as others have pointed out. So in this case it would make sense to leave them on for the duration of the printing session. A better procedure, however, would be to connect the sprial tubes to a light integrator.
Sandy
sanking said:
At first glance, the number appears to be big. But when you put it into a context, you might arrive at a different conclusion.
12 tubes at 40 watts = 480 watts
Assuming an 8-hour working session, that becomes 3840 watt-hours, or 3.84 kilowatt-hours.
Where I live, the local bandits (the utility) charge about 17 cents per kilowatt hour. So the energy cost for an 8-hour working session would be about 65.3 cents.
The B&S combo kit sells for about $150 and is supposed to be enough to produce about 20 8x10s. An 8x10 sheet of COT320 costs about $1. So the materials that go into one 8x10 print (regardless of good or bad) cost about $8.50.
Let's assume that you are really industrious and can produce 16 prints during that session. That means that the energy component of per-print cost associated with leaving the lights on throughout the session is about 4 cents.
When you look at it this way, the energy cost doesn't seem so significant.
Monophoto said:
The energy costs are just part of the equation. Leaving the tube bank on creates additional heat, makes it difficult to use the roon for other purposes, say coating and dryng of exposed material, and would not allow use of my integrator system.
From my perspective, the *only* advantage to leaving the lights on continually is bulb life. From the perspective of consistency in exposure there is no advantage at all since regular tubes reach full output within a few seconds of being turned on.
However, in workshp enviroments where several people are using the same light it makes sense to me to just leave the exposing unit on all the time, assuming the room is not being used at the same time for coating and drying of light sensitive materials.
Sandy
cperez said:
Most standard fluorescent lamps, and especially the compact and spiral types, do not put out enough energy in the blue and UV region to be practical for alternative processes. I've been able to use tubes with a standard daylight phosphor (like FT20D, not the special color corrected "sunlight" phosphor) with a bit more than a stop in speed penalty over the BL phosphor for cyanotype. There are "high actinic" lamps from Phillips and others that look good on paper, but I haven't tried them. Blue phosphor bulbs (types like FT20B) work very well, but they are even more expensive than the BL bulbs and are harder to find.
On a somewhat related note, I have looked at the Iwasaki H125-BL screw-in light bulbs (125 and 160w E27), hoping they may be viable for printing 5x7/13x18. The link: http://www.specialtyoptical.com//catalog/h125-bl_2712672.htm. From what I can understand of the manufacturers information they are giving out UV in the 360 nm (and over) range which should be enough. (?)
Even if they work, I still need to get a socket and cable to handle the 125 or 160w...
Even if they work, I still need to get a socket and cable to handle the 125 or 160w...
Jerevan said:
But these bulbs are not self-ballasted, are they? If not, you will need a fixture with correct ballast.
Sandy
Jerevan said:
These lamps require the use of a ballast. I think making a light box out of a bank of 36W or 40W BLB tubes will give a much more even coverage of UV over the surface of the print in a smaller box than using a single (or a number of) 125W BLB mercury vapour lamp(s). Buying a handful of ordinary fluoro battens and replacing the tubes with BLB type tubes is simpler than messing about with lamp holders, ballasts, power factor capacitors etc. (at least, I'm planning to go down the path of using the tubes).
John.
Thanks for the information - I managed to miss out on the Iwasaki bulbs needing HID ballast. I thought it was just a matter of finding a socket that could take the wattage. I also found them locally which was nice. You live and learn. Perseverance is the word of the day. One more go at it...
Now that we know which bulbs to use, how about the construction of the box? A friend and I just went in on purchasing 6 bulbs at 27 watts each. We figure this will adequately cover 8x10 on an 11x14 sheet of paper.
Are you guys building complete enclosed units? If so, how are you extracting the heat from the bulbs? Or is that a concern over a, say, 10min exposure?
Or are you guys building your boxes with at least one side open? If so, what, if any, concerns do you have for UV light spillage?
Are you guys building complete enclosed units? If so, how are you extracting the heat from the bulbs? Or is that a concern over a, say, 10min exposure?
Or are you guys building your boxes with at least one side open? If so, what, if any, concerns do you have for UV light spillage?
I designed my box to be completely enclosed, with a hinged door that one lifts to insert the printing frame. I put a small muffin fan on one corner, and a light-tight vent on the opposite corner to deal with the heat problem - the fan draws air in and it flows out through the vent - but I've noticed that the positive pressure inside the box also forces the door open. Not a problem - just a curiosity.
A muffin fan? Explain a little, if you could. Is that 10VDC? Or can it be rigged right up to 120VAC?
Which kind of light tight vent were you able to find for your project? Special order item? Or Home Depot grade materials?
Last thing, any issues in reversing the blower to reverse the airflow to "suck"?
Which kind of light tight vent were you able to find for your project? Special order item? Or Home Depot grade materials?
Last thing, any issues in reversing the blower to reverse the airflow to "suck"?
Monophoto said:
cperez said:
Chris - stop by Radio Shack and I think they have 120V muffin fans.
Also, you should talk with Neil as he recently made the ultimate UV printing box!
Kirk is bang 0n - Radio Shack has 120v muffin fans. In two sizes, as I recall.
As to blowing versus sucking - it's not rocket science. There's a little arrow embossed on the side of the fan tht show the direction of air flow. Once I got that through my thick skull, it was simply a matter of which way I mounted it on the box.
The light tight vent I purchased from Porters Camera Store sometime in the last century. It was lying around the house collecting dust, and needed a useful purpose.
As to blowing versus sucking - it's not rocket science. There's a little arrow embossed on the side of the fan tht show the direction of air flow. Once I got that through my thick skull, it was simply a matter of which way I mounted it on the box.
The light tight vent I purchased from Porters Camera Store sometime in the last century. It was lying around the house collecting dust, and needed a useful purpose.
Kirk, Louie, many kind thanks for the additional information.
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