Building a UV printer

Carlo Ponzoni finds the sun quite unreliable and builds his own UV printer to use for alternative photographic processes.

Writer / Carlo Ponzoni

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Printing alternative techniques in the sun is absolutely rewarding, environmentally friendly, free of charge, and seeing as the sun is a self-stowing device, this choice does not create mess in the home.

Unfortunately not only the weather, but also the sun elevation does not encourage repeatable results either. This leads to some frustration, a lot of paper waste, and the need for patience to coat, dry, and find leisure time in (adequate) hours of sunlight.

A UV printer helps. It is possible to buy it, but I found out that the price range may not be compliant with the budget of most amateurs.

Building the UV printer

After some unsuccessful tests with a set of general purpose lamps, including halogens and one incandescent black-light bulb, I admitted the need to go back to the drawing board. For me, the most useful reading was a paper about lamps for alternative techniques by King S. called Printing with Ultraviolet Light. Then I carried out some market surveys, both surfing the internet as well as stressing some shop attendants, and I ended up with a tube-style solution.

The choice of lamp style predetermines the shape of the UV printer, resulting in this case in a relatively flat, scanner like device free of thermal loads. If I had used a bulb lamp, the shape and dimensions of the overall equipment would have been different and probably less compact.

In the “fluorescent tubes” category, I searched for various light sources, beginning with the tanning ones. Despite the fact that commercial face tanning devices are relatively widespread, I had no success in buying single tubes. So I looked for some mosquito attracting lamps, which are known for emitting blue and ultraviolet radiation. Again, the chance of buying the lamps alone was not very high.

In my search, the only readily available lamp that could contain some UV spectrum, was one specifically for reptiles in a non professional environment, i.e. the home.

The advantage of such a choice is straightforward: it is a relatively eye-safe light source (at least when compared with professional UV lamps), readily available and relatively cheap. I started with just one lamp to verify the feasibility of this approach. It worked, so I decided to carry on with a more structured project.

The first step was to buy four lamps with their supports. If you look at figure 1, you could probably imagine that the width is unnecessarily long. And you’re right. In fact, I selected such a width because the cost of ordering this length was particularly cheap due to a special offer in the retail centre. I bought the wooden tables on the basis of the dimension.

Pine (or fir) is cheap, it is very easy to work with everyday devices, and many retailers offer a free cutting service. At this point the work is already coming together. The lamps are screwed to one of the tables, four legs are installed, and some wiring is put on the top to connect the lamps. I remembered to connect the metallic body to the ground and to group all the wires inside an electrical box. A switch, an electrical cordon ending with a plug, a couple of clamps to prevent stress on the cables, then some hinges, and of course a reflecting screen. To arrange this last component, I used a thin mount (which was the back of a broken frame in its previous life), and I covered it in aluminium foil.

Please note, do not attempt to wire lamps with high voltage if you are unsure of what you are doing, in that case, you need to consult a professional electrician!

Figures 2-5 show the final result. Some other things have been added, like the wooden handle, which is practical and adds a feeling of completeness.

I used a “frame thickness” glass, i.e. glass from a commercial frame. This kind of glass, the normal one (i.e. not the anti-glazing one), is the best. It is thin and has optical quality. I abandoned it temporarily, after discovering one thick glass in my garage (shown in Figure 1) which more or less matched the needed dimensions. Later I had some doubts about the transmission losses and the geometry of multiple reflections inside the thick glass. So I made a test, by exposing a negative-sensitive paper sandwich half covered by the thin glass and half by the thick one. I noticed a difference in exposure as well as better acutance by the thin glass.

The ceiling lamp is just the necessary width. Probably five lamps would have been more adequate. But anyway, to more or less “align” the paper to be exposed with the lamps I drew some lines, as shown. Pencil lines would have been alright, but I drew it with a pyro engraver, for a more permanent look.

I decided not to clad the sides of the printer to dodge the lamp’s light. This was to facilitate the natural convection. The four lamps I chose, Sylvania Reptistar 18W (Ref. 3), give 72 W spanned on a 25×60 cm surface. This is not so much, no thermal spot, or, in other words, the freedom of unattended exposure without risking a fire, but I preferred to maximise convection for further safety. Despite the fact that it is advisable not to look at the light emitted by the printer, I operate this assembly in the basement and the radiation from these lamps is home-compatible, i.e. it doesn’t pose any particular threats.

A daily timer from home appliances is sufficient for my process, due to a resolution of only 15 minutes, which is arguably a poor resolution also for my ¾ hour-long exposure with “my” traditional cyanotype, but it works ( I write “my” because I double coat the paper with a solution denser than usually recommended, therefore increasing the typical exposure time).
I also discovered that being forced to use few timing steps (1/4th, ½, ¾) is beneficial to me: I have to limit the combination of parameters.

According to literature, the “new cyanotype” requires less than 1/4t of the traditional one, or less than 15 with this assembly, and my tests confirm this. In this case I turn it on and off manually.
But what if a timer is preferred? The answer can be a staircase light timer, available in the 30 sec – 20 minute range with mechanical time settings.
If you have some additional free time to devote to it, a protective paint is helpful to counteract the unpleasant effect of fingerprints and dust. I preferred oil for furniture care, to preserve the natural appearance of pine.

Cost estimation
Material	Price in Euro
Neon lamps… (Sylvania, 60 cm long, 18W)	€12 x 4 = 48
Lamp holder (electronics included)	€ 8 x 4 = 32
Switch, plug, plastic box, electrical cordon	10
Wooden tables (no 2 tables 100cm x 60 cm x 1.8 cm)	25
Other (“legs”, hinges, bolts and screws)	5
Timer	10
Total price	€ 130

The price example assumes “buying from scratch”. So it is a bit overestimated.
For example I already had a spare daily timer (which, by the way, came in a box of two identical timers for some 9,90 €, total), or the bolts, screws, one of the wooden tables, the electrical wires, and so on.
A small “economic fall-out” came thanks to the lamp holders in the sales, which were equipped with “normal” lighting lamps, which I took off the holder and put in my stock of home spares.

Summary of how to build a UV printer

The lamps have already been discussed. Despite being the result of chance (I started looking for a professional UV 300 W bulb lamp, not readily available, and anyway at a cost of about 60€), the tube solution leads to a compact machine and does not include any thermal risk.

Is the exposure time too long? Thanks to the timer, I run it in the night, so one hour does not impact my productivity. I also black tone by the simplest process (direct immersion in coffee) which is more than one hour long and creates no bottleneck in the work line due the exposure process. The electrical consumption isn’t high either. This takes up less than 0.08 kW/print. Should a 300W lamp be used, with an exposure of 10 minutes, the energy demand would be 0.05 KW/print (anyway a slight environmental impact and an immaterial cost).

I also ask myself why I put the lamp bed in the upper part of the machine. Consequently the heaviest part turns over: the opposite concept of a copying machine. Probably I was instinctively driven by the sun exposure, where light comes from the top. But whatever the reason, this solution needs no glass screen to hold the glass-negative-paper-back sandwich, and so any exposure frame is adequate. In other words, the important thing is to sandwich the sensitised paper and the negative between a thin glass on a flat back surface. The top solution is a devoted contact print frame, and an elegant, self-made one, has been described on this website by Jim Read in Darkroom DIY: Making a contact print frame. The simplest one is to use a commercial frame, maybe the final one selected to display that photograph, which is useful to the process before hanging from the wall.

Then, the short distance from the bottom and the ceiling lamp is very questionable. In fact this is less than the inter-lamps distance, while it should be more. But I’m lazy and I did not change it due to apparently acceptable results: I have never noticed irregularly exposed strips.

Examples of cyanotype prints

To sum up, some cyanotype examples. They were exposed by this system, both with old and “new cyanotype”, with or without further processing. Should the readers appreciate this, I hope they will understand that the look of the images is closely connected to my skills and the performances of my printer, seeing as the subjects (Italian women and towns) are negligible issues.

Important note: no responsibility is taken either by the Author or by the Editor and Publisher, by any consequence related to the use of this information, as, for example, building this printer. Given that the printer is not for sale, no qualification of design and manufacturing has been carried out. Be very careful when using electrics.

Note: I am indebted to Katharine Walker, not a photographer (at the moment) but a professional English teacher, for her patience in transforming a text which vaguely resembles English, into a readable article.

References:

1. King S., “Printing with Ultraviolet Light“, accessed on 2009-05-23
2. Specifications for Sylvania Reptistar 18W, accessed on 2009-05-23
3. Read J., “Darkroom DIY: Making a contact print frame“,accessed on 2009-05-23

Carlo can be contacted on carlo_ponzoni@libero.it.