Problem with new UV lamp ???

[George Papantoniou]

I've purchased four 15-W Osram fluorescent UV lamps, thinking that they would make a nice light source for alt-processes. I've tried to make Cyanotypes with them (the classic way, not the New one) and it seeems that exposure times need to be really long (1.5 - 2 hours at a distance of 20cm from the lamp for a "normal" negative).

1. Do you have any experience with the specific lamps (they indicate that they emit UV-C) ? Are they strong enough ?

2. Might the Ferric Ammonium Citrate (green, from Silverprint UK) have gone bad ? How do I tell ?

3. Might I have used too much Potassium ferricyanate by mistake and lowered the sensitivity of the paper ? Should I use less of it next time ?

4. Will things be better (exp. time shorter) if I double - coat the paper ?

5. If the paper was alkaline, would that lower the sensitivity ? Should I try with another paper ?

 

[Jim Noel]

My first thought is that the bulbs are too far from the printing frame. A space of 5-6 cm would decrease your times considerably. Of course, they need to be far enough away to prevent banding. My fluorescent box has 8 tubes as close to gether as possible and are about 5 cm from the printing frame. Ptinting times for cyanotype run about 8-10 minutes.

Hope this helps.
Jim

 

[Joe Lipka]

Jim has the answer. Remember (or not) the old inverse square law for illumination. If you reduce the distance from the light to the negative by a factor of 4 (20 cm to 5 cm) your exposure time will reduce by a factor of 16. Exposures 8 to 10 minutes isn't too bad for a print from a film negative.

 

[George Papantoniou]

Thanks. I'll try it and tell you how it went. I am a little bit afraid of uneven exposure (banding), for the lamps are not mounted so close to each other. I had to use some mounts (one different for each lamp) that are relatively wide and so I cannot make the lamps stand closer than 5-6 cm from each other...
I'll also try to use different papers and double coating to see if it works better...

 

[xtype]

Which papers have you tried so far?

 

[John_Brewer]

My home made unit uses those short UV tubes found on Phillips face solariums. Behind the tubes is brushed alluminium. The tubes are 50mm apart and there is no banding. I might make another unit when I can find another face tanner with the tubes closer together which I would guess would increase the printing time. I don't think the inverse square rule applies with banks of UV tubes. I use my lights at about 150 - 200mm above the negative.

J

 

[George Papantoniou]

John, what's the wattage of your lamps (tubes) ?

I've tried four kinds of papers testerday. There was one Ingres, one schoeller and two other ones (I don't know their names). The ingres and the schoeller gave the best contrast and one of the other ones good sensitivity. I mixed a little less Potassium Ferricyanide with the F-A-citrate and this seems to have increased the sensitivity a bit, although it seems like half a stop or something. Double coating did absolutely nothing (except giving me "dirty" highlights, one one of the papers)...

I will have to construct a box for the lamps to be installed in and it's goind to have reflective inside surfaces, so the illumination will be better. I'll reduce the lamp-print distance, too...

I'll have to see what happens with other techniques, too... I'll soon try gum and platinum-palladium...

Cheers

 

[John_Brewer]

George

I'm away from home at the moment but the tubes come from a Philips HB171 unit. I have a pdf file on how I made it which you are welcome to have. Feel free to drop me an email and when I get home I'll email it to you if you're interested.

J

 

[George Papantoniou]

OK, here's some new data about the type of lamps I purchased :

They're disinfectant UV lamps, used to disinfect water and other stuff. Their output is 95% UV-C (peak: 254nm). They're quite harmful to living creatures...

Do you know whether this will work with alt processes, or might I have chosen the wrong type of lamp ?

 

[kevs]

Hi George,

I've purchased four 15-W Osram fluorescent UV lamps, thinking that they would make a nice light source for alt-processes. I've tried to make Cyanotypes with them (the classic way, not the New one) and it seeems that exposure times need to be really long (1.5 - 2 hours at a distance of 20cm from the lamp for a "normal" negative).

1. Do you have any experience with the specific lamps (they indicate that they emit UV-C) ? Are they strong enough ??

They don't seem to be the best choice. Mike Ware says: "There is no advantage, and much additional risk, in employing the more dangerous 'short-wave' ultraviolet mercury lamps which rapidly damage eyes and living tissue (UVB below 320 nm, at which point ordinary glass begins to absorb strongly, and UVC below 280 nm)." http://www.mikeware.co.uk/mikeware/preparations.html So it could be that your glass is absorbing the useful wavelengths.

Most folk who use tubes recommend Black Light (BL or BLB) tubes, the sort used in discos to make clothes glow. I've read that the Black Light bulbs (as opposed to tubes) aren't quite as good - they don't kick out that much UV.

2. Might the Ferric Ammonium Citrate (green, from Silverprint UK) have gone bad ? How do I tell ?

You can test it by making a cyanotype print or photogram using sunlight. That should indicate whether your lamps are at fault. Cyanotype is cheap - it'd be better to test with this before spending out on expensive metal salts. Then you can make sure the light source is suitable. IMO of course!

Cheers,
kevs

 

[George Papantoniou]

Hi Kevin. That's exactly what I was afraid of, since these lamps I got don't emit UVA or UVB at all (I was thinking about the glass absorbing some of the UVC, but did not have hard facts). I guess that my glass absorbs most of the radiation, leaving only a small part to do the job. Either I have to find a way to press the neg on the paper without glass (or a non-UV-absorbing glass) or change my lamps...

 

[xtype]

Attached are pdf's from two pages of Dr. Ware's 'The Chrysotype Manual' - gives UV wavelength info and a selection of papers which he's tested for use with the iron-based processes.

 

[George Papantoniou]

Thank you for the PDF's, they're quite heplful. I ordered 4 Sylvania BL lamps to test. I hope they'll prove more effective. I also have some Arches Watercolour paper to try.

The thing is, now I made a search on Google about the UV transmission of plain glass, I found out that it absorbs a big part of it (all frequencies further than 320nm, or something). It seems that quartz crystal glass lets UV pass through much more generously. Would it be a good idea to look for a 8x10 piece of crystal to use for my contact printing with UV ? Does it exist ? Is it expensive ?

 

[Jordan]

The thing is, now I made a search on Google about the UV transmission of plain glass, I found out that it absorbs a big part of it (all frequencies further than 320nm, or something). It seems that quartz crystal glass lets UV pass through much more generously. Would it be a good idea to look for a 8x10 piece of crystal to use for my contact printing with UV ? Does it exist ? Is it expensive ?

Hi George -- In chemistry labs we routinely use quartz cuvettes for spectroscopy in the UV range (around 254 nm). They're expensive. I would think that a cheaper route would be to go with the regular UV BLB-type bulbs (they generally emit in the 350-nm range) and use regular class.

I'm still printing with a single "compact fluorescent" spiral bulb that fits into a normal socket -- a 13 W BLB. I use it for cyanotypes and VDB prints.

 

[sanking]

Hi George -- In chemistry labs we routinely use quartz cuvettes for spectroscopy in the UV range (around 254 nm). They're expensive. I would think that a cheaper route would be to go with the regular UV BLB-type bulbs (they generally emit in the 350-nm range) and use regular class.

I'm still printing with a single "compact fluorescent" spiral bulb that fits into a normal socket -- a 13 W BLB. I use it for cyanotypes and VDB prints.

The spiral BLB tubes are now available up to 27 watts or so. That should reduce printing times a lot compared to the 13 watts tubes, if long times are a problem.

Sandy King

 

[George Papantoniou]

Thanks Jordan, Sandy for the tip. I am afraid the spiral BLB FL tube wouldn't be easy to find here in Greece. I ordered the 15W BL tubes, four of them and I hope it'll work. I read somewhere that the BL give shorter exposure times than the BLB (because it's the same type of lamp, but without the filter).

 

[George Papantoniou]

Got the Sylvania BL tubes. They need 3-5 minutes to expose a Cyanotype.... Funny how the other lamps needed at least 10x more time...

I'll see how it goes with other emulsions (gum, palladium) and hope it'll be OK.

 

[blackmelas]

Hey George,
Are you getting your materials for Cyanotype and the other processes locally or importing?
Happy holidays,
James

 

[George Papantoniou]

Hi James, glad you're back. How was the holidays back home ?

I find most I need in Athens, I can show you where anytime you want. For the green ferric ammonium oxalate I had to ask a friend who was in England to get it from Silverprint, but now I think it can be ordered here in Athens, too.

 

[Jordan]

The spiral BLB tubes are now available up to 27 watts or so. That should reduce printing times a lot compared to the 13 watts tubes, if long times are a problem.

Sandy King

Thanks Sandy -- This is good to know. Long times haven't been too much of a factor for me (I need about 10 mins to make a 4x6" VDB using a Pictorico OHP negative). Unfortunately there don't seem to be Canadian suppliers of spiral BLBs so I would have to order them from the USA as well.