Category Archives: Photographic Processes

Building a UV LED light box for cyanotype and lumen printing

The cyanotype and lumen printing processes are two of the more frequently practised alternative photographic processes, because of their overall simplicity and the fact there is little-to-no need for equipment. Most people will do their exposures outside in the Sun initially, but if you want to work with these processes on a regular basis it can be frustrating to have ideas ready to try, but be delayed by lack of a sunny day. While it is still possible to expose on cloudy days, the length of time required to obtain a suitable image is greatly increased. Working with the sun it is also difficult to figure out predictable exposure times as the intensity varies according to the daily weather, time of day and time of year.

The solution is to switch to an artificial UV light source which can be used any time of day or year, whatever the weather, always giving the same exposure time. Historically though, UV exposure units have been relatively expensive to obtain, £100 or more. The ongoing developments in LED lighting technology though have now opened up new possibilities for constructing a custom UV light source for minimal cost. In particular it is possible to obtain 5m long strips holding 300 UV LEDs from online marketplaces such as eBay, for around £15 / $20 (search eBay for keywords “5M UV 5050 SMD 300LED“).

 5M UV (395-405nm) waterproof 5050 SMD 300LED strip, powered by a 12 V @ 5 amp supply

5M UV (395-405nm) waterproof 5050 SMD 300LED strip, powered by a 12 V @ 5 amp supply

The 5M long 5050 LED strips are 1cm in diameter and can be cut every 3rd LED. If they are cut into groups of 15 LEDs, this will result in 20 LED strips, each 25 cm long. Arranged side by side, this allows for creating a light source that will evenly expose a 20 cm x 25 cm area which is practically perfect for both A4 and 8x10in paper sizes. If one didn’t mind lower intensity it would be possible to left a 1cm gap between strips producing a source suitable for 16x20in / A3 paper, at the cost of longer exposure times.

When cutting the LED strip up, it is important to cut exactly in the middle of the metal contacts between every 3rd LED, as it will shortly be necessary to solder wires onto the metal contacts. If using the waterproof coated LED strip, the rubbery coating will have to be removed from the contact pads after cutting, which is quite tedious and an argument in favour of the non-waterproof variants. With the strip cut into pieces, it is now time to connect them back together by soldering short (5-10 cm length) wires between the metal pads. While it is possible to wire them all together in series to form one long strip, this means the link wires will be carrying the full 5 amp current load and if any link goes bad it risks taking out the entire set of LEDs beyond it. A better bet is to wire them up in parallel, or perhaps grouped in a mesh giving multiple paths for the current, so the link wires only need handle a tiny current and there is redundancy. The important thing when soldering the link wires is to preserve the polarity between strips – ie connect positive to positive, and ground to ground.

All 20 strips with connecting wires soldered on. Mistakenly all 20 strips are in series. This was later resoldered to put them in parallel

All 20 strips with connecting wires soldered on. Mistakenly all 20 strips are in series. This was later resoldered to split them in 5 groups of 4 strips, each group in parallel, reducing current in the link wires to 1amp.

The vendors of the LED strips will typically also sell suitable power supplies. These mains powered units need to output 12 volts and be capable of supplying 5 amps to enable the LEDs to run at full brightness. Lower amperage PSUs will work, but the reduced LED intensity will obviously increase exposure times, so it is best to simply get the right specification of PSU from the start.

Mains PSU for the LED strip able to supply 12 volt at 5 amp

Mains PSU for the LED strip able to supply 12 volt at 5 amp

The power supply will likely have either a 2.5mm or 2.1mm plug, so a correspond matching socket needs to be purchased. While it is possible to just turn the device on/off at the wall, or by pulling the plug out, a better bet is to put a rocker switch inline with the positive power line between the plug socket and the LED strip. Again make sure the rocker switch is rated to carry 5 amps.

Power output is given by multiplying voltage by current, so 12 volt at 5 amps will produce 60 watts of power output. This is going to generate a reasonably large amount of heat and if something is not done about this, it will gradually degrade the LEDs shortening their lifetime. The obvious answer to this is to obtain a couple of 12 volt computer fans to fit in the case of the final light box. A fan that is approximately 4cm x 4cm in diameter will be ideal. They’re quite cheap so you might even consider using a pair of fans. The wires from the fan can be connected in parallel with the LED strips, since they’re conveniently driven from the same voltage. Do NOT connect them in series with the LEDs, as the 5 amp current draw of the LED circuit will kill the fans. Also be careful to get the positive/ground polarity right when connecting the fan, as reversing polarity will NOT make the fan run in reverse and likely kill the fan too.

12 volt computer fan, 4cm in diameter

12 volt computer fan, 4cm in diameter

The case for the light box will be made out of wood and comprise two pieces, a base which will hold the paper to be exposed and a slightly larger lid which will hold the LED panel. Both will have sides and be sized so that the base nests snugly inside the lid (or vica-verca). The top and bottom panels can both be cut from a sheet of 3mm plywood, the lid panel being 39×30.5cm and the base panel 36.5×25.5cm. These sizes are fairly arbitrary – the smaller simply needs to be about 2 inches larger than the size of paper to be exposed on each side. So for 8×10 paper, the smaller would want to be about 12×14 inches. For the larger lid, sides were cut from a length of 70x18mm timber, and nailed to the plywood panel. For the smaller base, sides were cut from a length of 36x10mm timber. In the timber sides of the lid, two 4x4cm holes were cut to hold the fans. Two holes were also drilled in the lid, one for the power supply plug socket and the other for the on/off rocker switch. When inserting the fans in the case, one should be oriented so that it sucks air into the case while the other should blow air out of the case, creating good airflow across the LED panel.

Light box lid showing the on/off rocker switch through the panel and power supply socket in the side

Light box lid showing the on/off rocker switch through the panel and power supply socket in the side

Close up of the lid, showing the computer fan inserted in the side to pull air across the LEDs for cooling.

The LED strip usually comes with a self-adhesive backing tape which is supposed to be able to stick the LEDs to most surfaces. This proved insufficiently sticky for me, so I applied super-glue instead. While the LED strips could be attached directly to the lid of the light box, it was thought preferable to attach them to a sheet of perspex or aluminium to allow the LED sheet to be separated from the case if needed. If using metal just be careful to avoid any short circuits with the link wires of the LED. Once the LEDs are attached, the sheet can be fixed to the inside of the lid with a couple of screws.

The larger lid, showing the metal plate with LED strips attached. At either end are cardboard shields to block UV light leakage through the fans.

The light box base

The smaller lightbox base, sized to be able to hold an 8×10 inch picture frame from a pound shop. Note a couple of screws sticking out of each side of the base, to prevent it sliding completely inside the lid when nested

When first turning it on, there was some UV light leakage through the cooling fans. Thus a couple of shields were cut from heavy duty cardboard and duct taped over the fan openings. With this in place there is no significant UV leakage from the light box, due to the closely nested lid and base. The UV LEDs are emitting at the end of the UVA spectrum, quite close to the start of the visible light spectrum, so the light is not a serious danger like UVB light would be, but it is none the less worth taking care to avoid accidental exposure.

In use the light box has proved to be intense enough to expose acceptable cyanotype images in as little as 5 minutes, and lumen images in anywhere from 10 minutes upwards depending on the visible effect desired. This is considerably faster than many commercially obtainable UV light sources that photographers have used in the past, which could take 15 to 30 minutes or even more. All together the cost of the complete box was probably around £45 – if you already have some parts in the shed such as plywood / timber pieces and a suitable power supply, then the price could be around £20-25. Either way, it will easily beat the cost of commercially produced light boxes and likely perform better too. The hardest part in construction is probably the soldering of the 50+ link wires between the LED strips. The case needs only minimal wood working skills – use of a saw and hammer. In summary creation of the light box is a very worthwhile use of time and money and will proof useful for years after.

Obsolete and Discontinued: a collective photographic project

The project background

This post is talking about my involvement in the Obsolete & Discontinued project which has just had its first exhibition at the Releva-T analogue photography festival in Spain. The seeds of the project were sown back in March 2015, when London based photographer & expert printer, Mike Crawford, was given a huge quantity of photographic paper (and a few rolls of film) by a client, David Yates. The paper had come from darkroom supplies left by David’s late uncle, Bret Sampson. There was quite a variety of paper, including Agfa Record Rapid, Kodak Bromesko, Agfa Brovira, Kodak Royal, Kentmere Bromide, Ilford Ilfomar and more besides. Most of the paper was so old – at least 20 years, perhaps as much as 40 years for some – that common opinion would suggest it to be mostly worthless and fit only for the rubbish. Thankfully Milke did some test prints to investigate the condition of the paper, finding some in fine condition, while others had heavy fog. Even those which had heavy fog turned out to be quite amenable to lith developer which was not nearly as badly affected.

After seeing these results, Mike unveiled a proposal to a meeting of the London Alternative Photography Collective (LAPC) meeting. He intended to give out batches of paper (~10-20 sheets per person depending on number of participants) to a group of photographic artists with an open brief to produce any type of work they wished. The only rule was for the supplied paper to be used in some manner, whether for the final work or just in an intermediate step. The idea was immediately appealing and many attendees of that meeting signed up to participate in the project straight away, myself included. After getting around 60 people signed up Mike sent out details on what paper was available (and its response with test prints) to all participants asking them to provide a preference list.

Developing the techniques & idea

At the time, having a 3 month old baby, I wasn’t really going into the darkroom at all, so using any kind of traditional black & white process was out of the question, never mind learning lith printing techniques. I decided to focus on alternative photographic printing techniques that could be done without any use of a darkroom, specifically the lumen and chemigram processes which I had recently started experimenting with in the back garden. I had trays suitable for 8×10 paper and wanted FB paper rather than RC. Beyond that I was not fussed on the choice, whether it was fogged or not, since this is pretty much irrelevant to the chemigram process which takes place in full light. Essentially any photographic paper will work for chemigrams no matter how old or badly looked after it is. Eventually I was given approx 15 sheets of Agfa Brovira G3 as the official paper to use for the project work.

Rather than risk wasting this precious paper, I bid on a couple of ebay auctions acquiring some ancient kodak and ilford papers for exploration of the techniques I wanted to use in the project. With the ilford paper I learnt how to combine the lumen and chemigram processes to create very pleasing hybrid works. Showing one of the works to some friends at another LAPC meeting, a remark was made that one of the prints (shown below) gave the impression of a river running through a city:

Resulting print after combining the chemigram and lumen processes.

Resulting print after combining the chemigram and lumen processes.

I myself felt that the dark brown / black texture of the print felt like a desolate landscape, devastated by industrial development or some natural disaster – quite representative of the state (reckless) human development can leave land in. At the same time I was feeling that too many chemigram images I’ve seen focused on the totally abstract and so wanted to explore how to control the chemigram process to bring in more recognisable forms.

Melding these thoughts together, my intent for the Obsolete & Discontinued project was to try to produce semi-abstract, but still recognisable, images of coastal cities around the world using the chemigram and lumen processes.

Behind the scenes

The starting point was to identify some coastal cities whose border between land and sea would give rise to reasonably recognisable outline and a good balance. In other words I spent a while browsing around Google maps looking at coastlines for random cities I’ve visited in the past. This identified a number of candidates including London (Isle of Dogs), Southampton (Isle of Wight), Plymouth, New York, Boston, San Francisco, Rio de Janeiro and Tokyo. With these identified I printed out the maps on plain paper and using a scalpel cut around the coastline to remove the land

Printed map outline after cutting away the land mass

Printed map outline after cutting away the land mass

The paper outlines were then traced onto pieces of 2mm thick card, then cut out with a scalpel again, to create the master heavyweight stencils

Cardboard stencil after being traced and cut from the paper outline

Cardboard stencil after being traced and cut from the paper outline

The purpose of the stencil is to assist in applying the resist for the chemigram process. The chosen resist was a thick paste of flour and water, the same that was used in earlier chemigram experiments. The stencil was placed on a sheet of the photographic paper and the resist spread on in a thin layer. The ultimate result was that flour paste adhered to the paper in the regions that would represent the land mass, while the sea remained clear.

Applying a resist of flour & water to the photographic paper, using the cardboard stencil

Applying a resist of flour & water to the photographic paper, using the cardboard stencil

The coated paper is then left overnight to allow the flour paste to dry out and form a hard crust on the paper. With the areas representing the sea still exposed, it was time to start on the lumen processing. The idea was to try to get an abstract texture to represent the rippling surface of the sea. To this end, several layers of crinkled clingfilm were placed over the paper in a random fashion, which would (in theory) control the amount of UV light affecting the paper.

Paper covered in clingfilm and placed in a photo frame ready for exposure under the sun

Paper covered in clingfilm and placed in a photo frame ready for exposure under the sun

The paper was placed in a budget photo frame obtained from a local pound shop (aka dollar store) and then left out under the autumn sun for approx 4-5 hours. The UV light had quite a nice affect on the paper turning it a fairly intense purple/blue color, and the use of cling film had been partially successful in introducing variation in the colouration.

The paper after it had been exposed to the sun for several hours

The paper after it had been exposed to the sun for several hours

The lumen exposure was immediately preserved by putting the paper through a regular fixer bath. Sadly with the Agfa Brovira paper, almost all of the colouration from the lumen exposure disappeared. This is entirely expected when fixing lumen prints, but the degree of fading varies across different papers and the Brovira seemed particularly badly affected. The final step was to slowly dissolve away the flour resist, moving the paper between developer and fixer baths every 10 minutes or so. Where the developer came in contact with the surface of the paper first, it would go dark gray/black, while the fixer would preserve undeveloped areas in pale brown. In this way the texture was gradually built-up as the flour resist dissolved. The chemigram stage took at least an hour of hard work per print to complete.

In the end six prints were made on the Agfa Brovira paper supplied for the project, and the three most successful ones were selected for presentation to the project.

Final results of the process on Agfa Brovira paper

Final results of the process on Agfa Brovira paper

My time producing prints for the project spanned a couple of months, with me snatching 2-3 hours at a time to work on it when the weather was favourable to lumen printing, in between the usual time consuming duties of parenting. The most time intensive part was the chemigram process where the dried flour paste would very slowly dissolve, but the results obtained were certainly worth the effort. Participating in the project helped focus the mind, allowing for intensive effort to control & master a particular set of techniques, with a clear target in mind. It has been a great learning experience and I’m very pleased to have gotten involved in it.

Creating chemigram images with caffenol ingredients

Over the past year or two I’ve done a bunch of experiments with the Chemigram process and even combined it with the Lumen process. In the work so far I’ve used various different substances as resists to control the action of the developer and fixer on the paper, thus influencing the pattern of the light & dark regions. Meanwhile for film processing at home I have been using my Caffenol-C-H-UK recipe almost exclusively as the developer. Caffenol is not just for film, it can be used for developing paper too and it occurred to me one day that instead of mixing up the caffenol in a jug, it might be interesting to just let the caffenol ingredients mix and react directly on the paper. So began a new series of chemigram experiments without using any kind of resist at all.

Caffenol is made by mixing washing soda crystals, vitamin C, instant coffee and optionally some iodized salt. The coffee and vitamin-C are the developing agents while the washing soda acts as an accelerator. The first step was to make a solution of washing soda and water and thoroughly soak the sheets of paper in it. The granules of instant coffee can be placed individually on the paper where needed, or simply sprinkled in an adhoc manner. The vitamin-C powder can just be poured or sprinkled onto the paper. The theory is that when the coffee/vitamin-c hits the wet paper it reacts with the washing soda to form caffenol on the surface. This is done in normal lighting conditions so the paper is universally and totally exposed and should gradually turn black where the caffenol has formed.

For this first test I used off-cuts of some outdated ~|40 year old) Ilford FB paper approx 5×4 inches in size. It was soaked in warmed (~25 C) washing soda solution then some coffee was sprinkled on, followed by some vitamin-C powder. After a minute or so it is possible to see hints of development along the edges where the paper is going dark gray

Caffenol chemigram initial stateAfter 5 minutes the developed areas didn’t appear to be getting any darker. I figured that since the paper was quite lightweight and moderately glossy, it was probably not able to absorb very much of the washing soda solution thus limiting how much caffenol can form. The washing soda is critical as an accelerator, without it coffee/vitamin-C are far too slow. So to try and intensify things I used a syringe to squirt on some more washing soda, which made the vitamin-C fizz very nicely. This image shows the run-off is developing the paper quite efficiently after just a minute or so:

Caffenol chemigram developing

The surprise came when I decided to wash off the ingredients. It turned out that the instant coffee had formed quite a sticky sludge which had adhered well to the paper. Given the limited water holding capacity of the paper, the areas with great concentrations of coffee granules had ironically developed the least. There is just a slight gray speckling effect where the coffee had a very limited action on the silver halides. The areas of most intense development were along the edges where the coffee and vitamin-C had mixed initially, and then in the broad areas of run-off which had well mixed caffenolCaffenol chemigram result

The process was repeated, but without pouring washing soda over the ingredients, just relying in that initially absorbed by the paper. The results were fairly similar to the first test, but with less development of the surrounding paper, as would be expected due to lack of run-off.

Caffenol chemigram resultThe results obtained were partially aligned with the initial expectations of the process but, as always when experimenting, there were surprises. In particular the inability of the paper to absorb sufficient washing soda solution was a key limiting factor in the results. It was surprising to see how the coffee + vitamin-C alone were fairly weak, but when they combined they became stronger than the sum of the parts. Finally the way the coffee became a sticky mass on the surface of the paper actually caused it to act as a chemigram resist, as well as a developer at the same time!

With the initial experiments successfully completed it was time to try some larger scale work with full sheets of 8×10 paper. The goal was really to just do more of the same but on a larger scale. The first work was fairly light on washing soda, thus forming broadly static patterns showing the texture of the vitamin-c powder and coffee granules, though there were some limited areas of runoff creating dynamic swirling patterns

Caffenol chemigramWith the second print the aim to was make a very dynamic image showing the motion of developing liquid on the surface of the paper, at the expense of any fine detail.

Caffenol chemigramPleased with the results of caffenol in a pure chemigram process, I decided to take it a step further and try to combine chemigram with a traditional B&W development process in the darkroom.

A while ago I took an simple photo of the Moon with a DSLR and teleconvertors which I then used to create a digital negative on acetate for printing as a cyanotype. Astrophotography is an increasingly popular endeavour for many people, but almost without exception the aim is to produce images with the best sharpness and finest detail the equipment will allow. An unfortunate result is that any two images of the moon will look broadly alike, and my own astrophotography images of the moon are no exception. So I decided that this digitally captured moon image would provide a good challenge as source material for creating a truly unique photographic print.

In the darkroom under safe light conditions, I placed a sheet of outdated Ilford FB 8×10 paper under the enlarger. The digital negative went on top of the paper for purpose of contact printing. From previous experience contact printing on this paper I just guesstimated the exposure at 15 seconds, with lens at f/8. The paper now has an invisible latent image ready to be worked on by the caffenol.

I soaked the paper in a washing soda solution, randomly sprinkled instant coffee and vitamin-C onto the paper and then just let it sit for a few minutes to give time for the caffenol to start working. Part way through I also added a very small amount more washing soda in some areas to encourage the development. After approximately 3-4 minutes (I wasn’t really timing this) I could see slight hints of the paper starting to turn gray in places. Washing off the caffenol residue though showed almost no development across most of the paper, which was initially disappointing.

None the less I now put the print through a regular B&W dev, stop & fix process. Rather than leaving it in the developer for the full 1 minute though, I noticed it was developing quite fast and choose to just move it to the stop bath when it “looked about right” – about 35 seconds. What was happening was that although not really visible yet, the caffenol had indeed kickstarted the development across the paper and the normal developer was just needing to finish off the process. If I had let the image site in the developer for the full 1 minute it would have been over developed and lost some of the qualities of the caffenol granulation.

The result was thus incredibly pleasing image of the moon, which I hereafter title “Moon through a dirty window”

Chemigram caffenol contact printLooking at the results obtained shows that the idea of using caffenol in a chemigram process has great possibilities for image making. On its own it can be semi-controlled to create attractive abstract images, while when combined with a regular B&W printing process it turn an otherwise plain image into an intriguingly textured pleasing artwork. I’m very much looking forward to getting back in the darkroom to further work through the possibilities this offers