Tag Archives: chemigram

An introduction to the Lumen printing process

I don’t have space for a darkroom at home, and while there are still a number darkrooms across London that provide training and rental, this quickly gets expensive and lacks convenience due to travel time involved. As such I have an interest in traditional photographic techniques which can be performed under normal interior or exterior light conditions. Film development requires nothing more than a changing bag to transfer the film to the processing reel. The cyanotype process only needs limited darkness after coating the paper while it dries, thereafter the actual exposure takes place outside in direct sunlight or via a UV exposure unit. While the chemigram process could be done in a darkroom, it is most commonly done in daylight as image formation doesn’t rely on light, but rather interaction of the chemicals to write onto the paper.

Continuing with this theme, the time came to try out the Lumen printing process. Many people are familiar with the photogram technique. Objects are placed directly onto light sensitive paper, which is then exposed under a enlarger, typically forming silhouettes of the objects where they blocked the light source. The paper is then processed in developer and fixer following the normal black & white printing process. This of course requires use of a darkroom.

Those who have handled traditional black & white photographic paper may have noticed that when it is exposed to daylight it slowly changes colour. Normally this would be a disaster making the paper useless for further photographic use. The Lumen printing process though, takes advantage of this behaviour in combination with a photogram like technique. Objects are placed directly onto light sensitive paper, and it is exposed to a light source, but this time it is either sunlight or a UV exposure unit. Over the course of the exposure, which can last anywhere from 20 minutes to several hours, the photographic paper will gradually change colour forming a silhouette of the objects. Once the paper is exposed, it would NOT go anywhere near photographic developer as that would just turn the entire paper uniformly black. Instead it is placed straight into a fixer bath, followed by an archival wash

The image initially visible after exposure can be quite intense, but this will sadly fade somewhat during the fix, and the colours will also typically shift in tone. The result is an image which is fairly low contrast with quite subtle tones. What is surprising is that despite the use of black and white paper, the image will actually exhibit significant colouration. This is markedly different from what is seen when creating photograms where the image is still strictly black and white and high contrast.

A simple lumen plrint made with planet cuttings. The image is fairly low contrast and mostly shows an outline of the plants.

There are a variety of factors which will influence the colours obtained in a Lumen print. A non-exhaustive list would include

Type of paper – each paper has a unique chemical formulation in its light sensitive coating(s) and as a result will behave differently when exposed to UV light
Age/condition of paper – the chemical formulation of the light sensitive coating(s) may change and degrade over time, depending on the way in which it was stored, which will in turn alter how it reacts with UV light
Time of exposure – the paper may undergo several colour changes as it receives increasing amounts of UV light. For example, it might start white, then go yellow, then blue. So varying the length of exposure will alter what colour the final image has.
Opacity of the objects – objects which are partially transparent to UV light will allow a range of exposures across the paper. Since colour is dependant on the amount of UV light, partially transparent objects can result in a range of colours being visible in the image.
Water on the paper – any water that is in contact with paper during exposure can influence the colours formed. The water can be applied manually, or it can leach out of the object (eg fresh cut flowers/plants) on the paper in the heat of the light.
Type of light source – while direct sunlight and UV exposure units both produce UV light, the sun provides a much broader spectrum, so will have a different effect than narrow band UV lamps. The sun is also a much more diffuse source than a lamp just millimeters away from the paper.
Toning of paper – the initial image will change and fade significantly during fixing. By toning the paper before fixing, it is possible to retain more intensity in the image and/or alter the colouring.

A Lumen print exhibiting varying colour tones. The image is dark purple where the paper was fully exposed, pale pink where fully obscured from light, and a yellow/brown where moisture from the leaves affected the paper

While some objects are heavy enough to make good contact with the paper and resist movement on their own, with others it might be necessary to weigh things down with a sheet of glass. This is particularly needed when using flowers and other plant material to form the image. There are a variety of options for this task. Those with existing darkroom equipment may well have one or more contact printing frames. These are quite expensive to obtain even on eBay, so more economical options are to obtain some suitable sheets of glass from a local glazing supplier, or use a cheap photo frame. With the prevalence of pound / dollar stores, finding cheap photo frames is remarkably easy. Why spend £50 on one contact printing frame, when you can buy 50 photo frames for £1 each. Being able to expose many prints at the same time will dramatically improve productivity, so it makes sense to go cheap and obtain many frames. It also means you won’t care if they get damaged or broken during use

An 8x10" sized glass photo frame from a pound shop, to use for contact print

An 8×10″ sized glass photo frame from a pound shop, to use for contact printing

One important thing to note is that the photo frame should have quick release clips for the backing board, not tacks that require pliers to remove and a hammer to re-insert !

An 8x10" sized glass photo frame from a pound shop. The quick release clips allow easy changing of paper.

An 8×10″ sized glass photo frame from a pound shop. The quick release clips allow easy changing of paper.

To use them, open up the back place the objects onto the glass in the arrangement desired. Remember to flip the arrangement left-to-right at this stage, since you’re looking at the image from the back, not front. Then place a sheet of B&W photo paper on the object, so the emulsion side is in contact with the objects. Finally replace the photo frame back and secure the clips in place. There should now be good contact between the objects and paper to ensure they are held still and make good contact for crisp edges. The pressure also helps to squeeze fluids out of plants which can help with colouration of the print.

With the frame prepared, flip it over, place it in direct sunlight and leave it for a while. Over time the colour of the paper will change where it is exposed to the UV light. At a minimum 15-20 minutes will probably be needed, but don’t be afraid to leave the image exposing for hours. Given the length of time involved, it is worth preparing many frames and exposing them all at once. When the desired arbitrary amount of time has elapsed, disassemble the frame to remove the photo paper and place it into the fixer. As mentioned earlier, the intensity of the image will fade somewhat and the colours may also change significantly. Once an archival fix and wash is completed though, the image should be stable thereafter.

The cyanotype process is often said to be one of the simplest to photographic techniques to teach people, but it is clear that the Lumen process gives it a good run for its money. If preparing your own materials, cyanotype requires a little bit of care in mixing the right quantities of chemicals for coating the paper. The Lumen process requires no preparation of the paper – it is merely necessary to mix up fixer at the documented dilution factor. There is a slight burden on Lumen printing when it comes to disposing of the fixer, as it will become increasingly contaminated with silver as more sheets are fixed. Overall though it is a quite straightforward and satisfying process to work with. It is hard go go wrong, beyond exposing for too short a time, so even with no prior experience you’ll get some decent results.

Experiments with the chemigram process, part 2

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The first part of this blog post looked at the use of honey, artists varnish and masking fluid as resists, along with use of cardboard stencils. This second part will consider two further resists and a method of creating a “stamp” for printing.

Wood varnish resist

After the disappointment of the artists’ varnish, some traditional exterior wood varnish was picked as a possible resist. The varnish is very thin, so after it was applied to the paper all the brush stokes just disappeared in a matter of seconds, resulting in a perfectly even coating. Once again Ilford multigrade RC paper was chosen, combined with Fotospeed fixer and Caffenol-C-H-UK. The varnish dried overnight for about 16 hours total resulting in a fairly tough finish on the paper. Since there was no texture in the varnish resist, it was decided to intentionally damage the resist. For one of them, a compass and blade were used to create circular arcs across the paper. For the other a series of horizontal and vertical lines were made with a knife.

Wood varnish resist applied to paper. When try, varnish was scored with a compass and blade to form circular arcs

When immersed in the chemicals, the varnish resist proved very resilient and non-porous. The places where the resist had been scored with a blade allow the chemicals to penetrate by a tiny amount. After 5 minutes in either the developer or fixer, the varnish showed no sign of disintegrating, so it was decided to try rubbing the resist where the cut marks were. With some hard work this gradually exposed more paper to the chemicals. After going back & forth between developer and fixer a couple of times, the alternating bands of black & white started to appear. A problem that occurred was that the emulsion on paper started to peel up in places where the varnish had been cut, as the cut had penetrated into the paper too. Removing the large extents of varnish proved very difficult indeed – using the friction between rubber gloves and the varnish was the only way and it took about 30 minutes for an ~6×4 inch print.

Wood varnish applied to the paper as resist, and left to dry for 24 hours. Lines scored in the varnish with a blade

The second sheet with the straight cuts rather than circular arms worked in much the same way. One interesting difference was that some of the areas exhibited a slightly purple tint, possibly where the developer only had a brief chance to work, before being fixed. Again there was a problem with the paper emulsion peeling up. Overall the graphical results of both images were very attractive, clearly showing the tell tale light & dark bands where the resist gradually came away. An easier way of working with the varnish may be to not let it completely dry – perhaps leave it to dry just enough that it no long runs off the paper. That may allow the developer & resist to penetrate more quickly.

Stamps

Following on from the idea of applying the developer to the paper selectively, it was decided to experiment with creation of a simple stamp to imprint an image on paper. For this purpose a piece of 5mm foam board was cut to size, to roughly match that of the paper. There needed to be some material applied that would absorb the developer. For this purpose some lengths of ordinary household string were superglued to the foam board.

String spiral stuck onto foam board to act as a stamp for applying developer to the paper.

String trails stuck onto foam board to act as a stamp for applying developer to the paper.

As can be readily seen from the images above, the designs are very simple / crude, just enough to examine whether the general concept is workable. This time Fotospeed print developer was used instead of Caffenol, and it was painted onto the string with a brush. The board was up-ended to allow any excess developer to drain off before it was turned upside down and pressed down onto the paper. The stamp was left in contact with the paper for about 60 seconds.

Print resulting from application of developer to the string spiral stamp.

Print resulting from application of developer to the string trail stamp. Some gaps in the image due to warped board

The results are pretty much as expected. The places on the paper affected by the developer were fairly tightly controlled. There were some gaps where it didn’t make good contact with the paper, mostly due to fact that the foam board was slightly warped. With a well made stamp, the general approach could allow for reasonably detailed figurative images to be created.

Flour paste resist

For the final experiment another type of resist was tried out. Taking a small quantity of regular baking flour, water was slowly added until a thick paste was formed. Two sheets of expired Ilford FB paper were then coated as evenly as possible with the resist and left to dry. As should be expected from fibre based paper in contact with water, it curled up hugely when the paste was applied. The flour paste resist was left to dry for 24 hours, during which time the surface started to crack up slightly

Expired Ilford FB paper covered with flower resist and allow to dry and crack.

The theory behind the use of a flour paste, was that the once dry it would provide a relatively hard & well attached resist, that would none the less dissolve fairly easily in the developer/fixer. The dried papers were placed alternately in the developer and fix baths for a couple of minutes at a time. Gentle rubbing was used to encourage the resist to dissolve and come away from the paper. Flexing the paper also encouraged further cracks to form in the resist which allowed the chemicals to work their magic. At times moderately large lumps of flour could be detached from the paper.

Image created from dried flour and water resist.

The results of the flour paste resist were quite satisfying. The distinct channels / lines in the image come from where the dried resist had cracked up. There was a reasonable degree of control over the image thanks to the ability to gently prise off chunks of the resist where needed. There was clearly still a very high degree of randomness involved in the images though, so rather than saying the process was controlled, it is perhaps better to say it was just influenced. The images apear to bring to mind the idea of organic cellular structures.

The two resists illustrated in this part of the blog were both much more successful than those from the first part of the blog. The wood varnish and flour paste were both very effective in the way they allowed interesting images to form, but the results have very different characteristics and the way they were worked in the chemicals was very different too. These results clearly show the importance of choosing the right type of resist to achieve the desired graphic effect on the final image. Experimentation and an open mind is key, because it appears hard to predict how any individual substance will perform in the real world.

With a set of experiments out of the way, now it is time to move on and attempt to create some presentable works of art.

Experiments with the chemigram process, part 1

Honey resist

For the first attempt at making chemigrams, I used Ilford Multigrade RC paper, and covered it in a resist of set, but still easily spreadable, honey. I applied the honey with a kitchen knife and attempted to smooth it out as much as possible over the entire sheet of paper. None the less it was still a fairly uneven thickness. Fotospeed FX30 odourless fixer was paired with Caffenol C-H-UK developer and water stop bath. It immediately became apparent that caffenol is not the best choice of developer for chemigrams. Functionally it worked just fine, but practically it was a pain as the opaque brown colour prevents the changes in the chemigram being visible without removing the paper from the dev. Still, we must work with what we have at hand, and that happened to be caffenol this time.

The paper was switched back and forth between the developer and fixer, allowing anywhere between 30 and 120 seconds in each chemical at a time. The honey resist proved fairly stable, adhering to the paper well and gradually dissolving over about 10 minutes. There was little need to agitate the trays nor to manipulate the resist.

Chemigram with a resist of set honey.

The darker black and pure white areas seen at the edges and just below center were a result of the paper being exposed to the developer and fixer for their nominal processing time (~120 secs). The paler grays and dirty whites were a result of shortened exposure to the chemicals (~30 secs). The alternating bands of dark and light clearly illustrate how the resist was gradually dissolving while being switched between chemical baths.

Artists’ varnish & masking fluid resist

In a visit to the local art supplies store, I discovered a variety of different products that could serve as resists for the chemigram process. A random choice resulted in the acquisition of a bottle of Windsor & Newton Artists’ Acrylic Matt Varnish, and a bottle of Windsor & Newton Colourless Art Masking Fluid.

Artists varnish and masking fluid, to be tested as potential chemigram resists.

Once again some Ilford multigrade RC paper was used, three pieces were coated with the varnish and three pieces were coated with the masking fluid. In all cases the fluid was applied using a small paintbrush, but to investigate the effects of brush stroke pattern on the final image, different patterns were used when applying the fluids. In one the brush strokes were diagonal, in one they were horizontal and in the other they were completely random swirls. Interestingly there was an immediate effect on the colour of the paper – masking fluid turned it immediately blue while varnish turned it immediately pink. Neither colour would ultimately persist in the final image, so this difference in behaviour doesn’t appear to have a practical use.

Papers coated with artists’ masking fluid (left hand column) and artists’ varnish (right hand column)

Once the resists were dry (only a matter of an hour or so) they were intentionally damaged. On some of the sheets of paper I used a knife to score some straight lines across the resist, while on others I used a compass with blade attachment to score some circles / arcs. The varnish was easily penetrated by the blade without applying any pressure. The masking fluid resist was slightly more difficult to score as it had quite a rubbery texture when dry – a sharp blade was required. Even now the rubbery dried masking fluid would come off the paper without much effort if rubbed.

As before the chemicals were Fotospeed fixer and Caffenol-C-H-UK developer. The sheets of paper were fully submerged in the chemical baths at each step, going back and forth several times. The artists’ varnish resist did not have much permanence, dissolving and flaking off in the chemicals very quickly. The image was almost entirely based on the pattern of the brush strokes used to apply the resist – scoring the mask had no perceptible effect. The developer appeared to penetrate the resist depending on its thickness to darken the image and the fixer removed the rest of the resist.

Windsor and Newton Artists’ Acrylic, Matt UV varnish resist. The only texture shown in the image matches the brush strokes of the resist. The chemicals penetrated the resist quickly and it dissolved & flaked off before any alternating bands would form

The resist using masking fluid was somewhat more satisfactory. It did not appreciably dissolve in the chemicals, not did they penetrate through the resist. The chemicals could work on the paper in areas where the resist had been scored with a blade. Rubbing on the resist would cause the rubbery mask to come away from the paper, though a gentle touch was needed otherwise massive amounts of resist would come loose in one go.

Windsor and Newton masking fluid resist, with circular marks scored into the resist with a compass and blade. Developer was first bath, hence black border

Windsor and Newton masking fluid resist, with straight lines scored by a knife. Fixer was first bath, hence white border.

Overall the artists varnish proved a disappointment, while the masking fluiding showed some hints of promise when damaging it with a knife. The ease of removal of the masking fluid when the image was finished was particularly appealing.

Stencils

For this experiment, instead of using a resist to control the action of the chemicals, it was decided to make a stencil. A piece of 3mm thick fibre/cardboard was used for the stencil and various circular holes were cut using a compass fitted with a blade. In addition, some pinprick holes were made randomly in the card

Piece of cardboard with spheres cut out to act as a stencil for applying developer/fixer to paper.

For its first use, developer was chosen as the chemical to paint in through the stencil. This resulted in a predominantly white background, with areas of black where the developer was painted. From the results it can be see that the developer soaked into the cardboard and run underneath the edges, so the outline on the image is far rougher than the stencil. There is an attractive highlight around the edges of the circles though – this appears to be something to do with the ineraction of the surface tension of the developer and the edge of the stencil.

Cardboard stencil was placed on to the photo paper and developer painted into the holes. Developer washed off and then image fixed.

For the second use of the stencil, the fixer was picked as the first chemical to apply. The cardboard was fairly contaminated with developer from the first usage, which no doubt had an impact on the effectiveness of the fixer. The fixer was not left to act for long enough either. When the print was moved into the developer bath to form the background, even the areas exposed to the fixer initially darkened.

Cardboard stencil was placed on to the photo paper and fixer painted into the holes. Fixer washed off and then image placed in developer, followed by a bath in fixer.

The stencil idea is promising, but further investigations are needed to identify a more suitable material to use as the basis of the stencil. At the very least a less porous form of cardboard seems necessary. Alternatively it might be interesting to the use the stencil as a mask for the applying the resist, instead of directly applying the developer/fixer.

In the next part of the blog post, some further types of resist will be illustrated along with a method of creating a “stamp” for printing with chemicals.

f/138 – Daniel Berrangé

Photography.Art.Astronomy.Science