Building a Spectrophotometer

In the autumn of 2025 I attempted to build a spectrophotometer by myself.

A spectrophotometer is a scientific instrument that measures the amount of electromagnetic radiation, or light as it is commonly known, that is absorbed by a sample. As different molecular bonds absorb light at different wavelengths, the absorption of light says something about your molecular composition. The most practical use for this is the determination of the quantity of a known substance in a sample.

In order to measure the absorption accurately, the light that passes through a sample is ideally only comprised of a single wavelength. This is a major difficulty in the design of the instrument, which can be overcome by something called a monochromator, of which the Czerny-Turner monochromator is the most common design.
In a Czerny-Turner monochromator, light from a white light source is aimed a concave mirror, which sends the light towards a movable grating that diffracts the light and breaks it up into individual wavelengths. These are then focussed by another concave mirror and aimed at a narrow slit, which in theory only lets one wavelength of light through. This light then passes through the sample and the reduction in intensity of the light is measured:

So while the principle of a spectrophotometer is simple, manufacturing its parts to analytical standards requires high precision, and therefore these machines are expensive. Brand new instruments are several thousand euro's and even decades-old equipment can still fetch prices of several hundred euro's. For example, this beauty from the 1970's is listed for 500 euro's today:

Because its principles are relatively straightforward and can be observed with the naked eye, the spectrophotometer is often an early introduction to scientific equipment within an educational context. Indeed, many teaching kits are commercially available, to make it possible to see the inner workings of the instrument and freely manipulate the individual components around. However, such teaching kits still aspire to the same level of quality as the commercial equipment and so the prices are still high, often exceeding a thousand euros for a basic model.

Due to the accessible nature of the machine's workings, there have also been many published instances of spectrophotometers built out of simple(r) materials and on a small(er) budget. Examples include Peiera, et al. (2019), Kovarik, et al. (2020), Shin, et al. (2022), Osterheider, et al., (2022), and Poh, et al. (2021).
However I noticed a pattern in these suggestions. They tend to be either limited in functionality, restricted to light of a single wavelength, or are only applicable to a small number of known analytes.
The more general purpose designs I've encountered on the other hand tend to incorporate at least one 'cheap' component that is nevertheless a considerable expense, such as a professional grade grating mirror, access to a 3d-printer, or a smartphone equipped with a camera. While such items are somewhat commonplace, if one has to purchase one specifically for the project, it quickly drives up the cost to 100+ euro's. 

With this in mind I went to make a spectrophotometer of my own design, based on the Czerny-Turner monochromator. My first goal was to make a functional general purpose spectrophotometer and the second goal was simply to spend as little money as possible.

In order to achieve this I aimed my attention at the cheapest materials I could think of that could perform the required function in my design.
For the monochromator I therefore used a rechargeable LED-flashlight as the light source. The price of the flashlight was seven euro's. Its light was reflected by two plastic make-up mirrors and broken up with a cd, for a total cost of another seven euro's. The whole thing was made of recycled wood, with the slit being a cut in a thin piece of veneer, attached by some tape. The wood consisted of scrap material from other projects, but let's value it at a generous five euro's.
The detector consists of an Arduino board with a € 0,40 phototransistor and a two-line lcd-screen. Together with a breadboard and some other bits and pieces this came in at a total of € 15,05.

The total cost of my spectrophotometer, if one had to build it from scratch, thus came in at 34 euro's and five cents. For this money you get a design that is compatible with standard (disposable) cuvettes that are used throughout the industry:

And an overhead view of the instrument in operation:

Of course the instrument I built is not plug and play and there are a few things I learned about its limitations.
The light yield is low due to the low quality of the mirrors that lack a uniform focal point. Therefore the amount of diffusion is high towards both ends of the visible spectrum, making the instrument the most effective in the green to orange colour range.
I also found out that a phototransistor was much more sensitive in this case than a photoresistor, and the transistor also had a more consistent output throughout the whole spectrum, while the sensitivity of the photoresistor I tried was greatly reduced above ~600nm.
Also the slit in the veneer is still somewhat broad, even if it was cut with a sharp scalpel. Therefore one can only measure the absorption in a broad-ish range of about 50 nm instead instead of a single wavelength.

In terms of its practical use, the calibration calculations have to be performed by hand. First the maximum absorption of the sample is determined, before a blank and a series of standards are measured against that point of maximum absorption.
As there is no (reliable) way to record this specific maximum, repeatability of experiments is a possible issue, as the measurement cannot be repeated exactly with known wavelengths.

Nevertheless, I found the instrument to be accurate and reliable with solute concentrations as low as 1 mg/mL. This is much less sensitive than commercial models, which can often reliably detect concentrations of 1 mg/L or even lower, but it's perfectly useable for my personal applications.

By not attempting to adhere to modern analytical standards, I have thus been able to build a functional general purpose spectrophotometer compatible with standard single-use cuvettes for about the same price as a single package of these cuvettes.

I can't stop reading!

I don't think I ever spoke about it here, but I don't particularly enjoy the writing process. In all honestly, I don't really like reading, neither.
Yet I like to learn, so I'm forced to read, and I believe things need to be expressed that aren't said elsewhere, so I'm compelled to write.

In the last couple of weeks, I've bought more books than I have time to read, while checking out some books from the library to boot. My own irrational behaviour puzzled me, until I realised I was feeling particularly anxious and troubled by the world. Ever since I was a child, I've tried to soothe my worries by gaining knowledge, and a greater comprehension would often lead to me to feel separated from the rest of the world. This isolation led me to seek a greater understanding and that greater understanding would make me feel more isolated.

So, for this, my 200th post on this blog, let me paraphrase the lament uttered by Fat Bastard in Austin Powers: The Spy Who Shagged Me:

I read because I'm unhappy.
I'm unhappy because I read. 

It's a vicious cycle.

Contributing Factors in a Cheerios-based Adhesive

One day, a few years ago, I ate a bowl of cereal and I haphazardly forgot one piece of cereal in the bowl. I then also neglected to wash the bowl for a number of days, causing the milk to dry out. When I picked up the bowl again, I noticed that the piece of cereal, Cheerios, was stuck firmly to both the spoon and the bowl.

Being interested in the potential of such a Cheerios-based adhesive, I decided to 'glue' a spoon to a window by dipping the Cheerios in milk and clamping it between a spoon and a piece of glass:

 Seen from the side it would look like this:

I didn't really have any idea of how it worked at the time, but knowing that both metal and glass are two materials that are often difficult to stick together, it was striking to me that Cheerios, when combined with milk, would be able to act as an adhesive for these two objects. 

I never quite figured out how to clearly show that it was in fact the combination of milk and Cheerios that kept the spoon in its unusual place, so it never went very far as an artwork.
However, it still intrigued me from a chemical point of view, as it was an odd combination of materials to be stuck together so easily. Adhesion of such dissimilar materials is often very much influenced by mechanical adhesion. In mechanical adhesion, the (invisible) roughness of a surface is filled up with a material that is liquid at first but then hardens to a solid. These two materials are then not chemically bonded together, yet they can't move as there is no physical space to do so. 

It was however unlikely that this is the full story in this particular case, as both glass and metal have relatively smooth surfaces and nothing in milk actively polymerises as it dries. There are therefore very few cavities to fill and no obvious substance to fill them with.

Being interested in surface interactions for another project, it occurred to me that the electrostatic activity on the surface of the metal, combined with the free electron pairs in the silicon dioxide of the glass, could perhaps create non-trivial hydrogen bonds with the sugar molecules in the milk. The Cheerios are in turn largely comprised of long chains of sugars, so that the sugar from the milk can form hydrogen bonds with those and possibly have an intertwining crystallisation structure, providing rigidity. 
This combination is partly illustrated in the following diagram, where (1) denotes the crystal lattice of the metal and the free electron pairs on the surface, (2) are hydrogen bonds with the sugar molecules, (3) are the sugar molecules that are left over when the water has evaporated from the milk, (4) are the hydrogen bonds between the sugar from the milk and the polysaccharides from the cereal, and (5) are those polysaccharides.

 

To test the plausibility of this hypothesis, I devised several experiments where different combinations of materials were tried out iin order to isolate and test a number of variables.

For these experiments, single Cheerios were placed in liquid and left to soak for 30 minutes. The liquids used were semi-skimmed milk, water, or water with an amount of sugar dissolved in it.
The wet Cheerios were then placed on a glass or plastic surface, and a spoon was placed on top. The spoons were balanced so that their own weight pressed upon the Cheerios.
This was then left to dry for ~3 days.
The degree of adhesion was then determined by the experimenter through detaching the materials from each other. This could result in either low, or no, tack (denoted as --), some tack (denoted as +/-) or high tack (denoted as ++).

The results of the various experiments can be found in the following table:

Materials	Result, Expected	Result, Observed
Glass, Spoon (std), Cheerios, Milk	++	++
Glass, Spoon (std), Cheerios, Water	--	--
Glass, Spoon (std), Cheerios, Sugar Water	++	++
PolyPropylene, Spoon (std), Cheerios, Milk	--	--
PolyMethyl MethAcrylate, Spoon (std), Cheerios, Milk	++	+/-
Glass, Spoon (smth.), Cheerios, Milk	+/-	++
Glass, Spoon (std.), Milk	+/-	+/-
Glass, Spoon (std.), Sugar Water	+/-	--
Glass, Spoon (std.), Kitchen Paper, Milk	++	-- & ++

The expected result was the result based on the theory as outlined above and the observed result is what actually was the case. It's clear to see that the expected and observed results match each other closely.
There were a couple of instances where the observed result differed from the expectation, however, namely in the case of the PMMA substrate, a smooth metal spoon, sugar water in the absence of cereal and the substitution of Cheerios for kitchen paper.

The observation that there was high tack in the combination of Cheerios with both milk and sugar water, while there was no adhesion at all when the Cheerios was only soaked in water, shows that the presence of sugar is very important in the adhesive properties of this combination of materials.
That the Cheerios with milk showed high tack on glass, some tack on PMMA and no tack on polypropylene also indicates that hydrogen bonding is very important to the adhesion to the glass substrate, as was expected.

An experiment done with a spoon that had a very smooth surface also shows that the observed adhesion is chemical or electrostatic, rather than mechanical, in nature. It was expected that a smoother surface would give less adhesion to the spoon, yet no discernible difference was observed between a well-used spoon and a new, smooth, spoon.
Two experiments performed with only milk and sugar water in the absence of Cheerios showed that sugar alone can't act as an effective adhesive for these materials. While the sugar stuck firmly to the glass, likely through hydrogen bonding, it showed virtually no adhesion to the metal spoon. Nevertheless, a thin droplet of milk did have some tack to the metal, so that some other component of the milk must be the substance that binds to the metal. The most likely candidate is calcium, as calcium ions are very large and able to form complexes with a high coordination number, thereby binding various molecules together.

To examine the influence of the Cheerios, an experiment was performed where a wad of kitchen paper, made out similarly long polysaccharides, was soaked in milk.
This gave an interesting result, where this wad strongly adhered to the glass, but showed no tack on the metal surface. This is most likely caused by the greater absorbance of kitchen paper, so that the sugars or ions in the milk where in little contact with the metal as the water evaporated.

In conclusion, when using Cheerios and milk as an adhesive for metal and glass, all four components are important contributors to the overall effect. A major contributor to the adhesive strength is the large amount of sugar found in milk, which is aided by other components, where an abundancy of calcium likely aids in bonding to the metal of the spoon. The combination of milk and Cheerios binds to the glass through hydrogen bonding and to the metal by some other chemical or electrostatic force, where mechanical adhesion only has a limited contribution.

Methyl Mercaptan

Artists like to use molecular models for making sculptures. This has already been covered on this blog, but I'd like to expand on the subject a little further in this post.
Molecules have certain stable configurations, which are governed by the distribution of their electrons. This is described by something called valence shell electron pair repulsion theory. It's somewhat complicated, but just imagine that electrons are magnets on a sphere that want to be as close to the centre as possible, while being as far apart from each other as possible. So while atoms are always in motion, this means that on average they are found in only a small number of configurations in molecules:

 

 

This kind of spatial configuration is correctly rendered in the large sculpture 'Gas Molecule' commissioned from Marc Ruygrok by the NAM:

This sculpture is supposed to depict methane, or CH₄, with a central carbon atom connected to four hydrogen atoms. Ruygrok has largely copied the common 'ball-and-stick' molecular model, only taking some liberty with the colour scheme.
Although molecules don't have a 'real' colour, there is a convention, called Corey-Pauling-Koltun colouring, for using certain colours for certain atoms. The central atom in Ruygrok's model is carbon, which in this convention is always associated with black, while blue is always associated with nitrogen. If the shiny purple-ish hue of the central atom is considered significant, then this is traditionally linked to phosphorous, but is today more commonly associated with potassium.
These colours are nothing but conventions, so it's not that Ruygrok's choice is wrong per se, but it also isn't 'right' to use blue in this case. Without any other information, any chemist will think this model represents ammonium, not the intended methane.

As already stated, this example uses the so-called ball and stick model, but a more realistic space filling model exists where atoms are depicted as overlapping spheres representing their Van der Waals surface. Molecules in this model consist of interconnected spheres, so that a good separation through size and colour becomes even more important than it is in the ball and stick model. With this in mind, let me present to you 'Calcium 4-[4-(2-methylaninlino)-2,4-dioxobutyl]diazenyl-3-nitrobenzenesulfonate (C.I.13940)' by Jean-Luc Moulène:

This is supposedly a model of the molecular structure of a pigment, Yellow 62, which is then painted in the colour of this pigment. I already pointed out that without adequate differentiation through colour, such a model is hardly able to serve its clarifying function.
It is however clear that Moulène didn't correctly render the molecule he meant to render. When I looked up and drew a model of the pigment, I came up with the following structure:

Even without knowing anything about chemistry, it's obvious that these are are two different structures. In the correct model, there are 41 spheres present, while in Moulène's sculpture one only counts 29 spheres. I did notice that in Moulène's sculpture no hydrogen atoms were depicted, which is somewhat common practice. I therefore counted the amount of hydrogen atoms that should be present, of which there are 15, so if the difference came from the absence of hydrogen, then the amount of spheres would be 26. I therefore have no explanation of where the artist went astray in rendering his model, but it is clear that the molecular model doesn't depict the pigment that he claims.

This could also already be gleaned from the inclusion of 'Calcium' in the sculpture's title. Organocalcium compounds are very uncommon and so the inclusion of calcium in the name most likely means that this is a salt. The SO₃^1- sulphonate group in the molecule, shown in yellow with red, is very reactive  and needs to be ionically bonded to a positively charged atom, Ca²⁺ in this case, to be stable. The double positive charge on the calcium ion is paired with two single negative charges on the other compound, which means that there must be two of the previously shown molecule in the following configuration:

This is of course looks nothing like the molecule in Moulène's sculpture and anybody with knowledge of chemistry could have spotted the error merely from the first word of the title. 

I then noticed the following drawing on the cover of Keith Tyson's publication 'Molecular Compound No 4.':

Comparing this image with the VSEPR models at the beginning of this post, it should be clear that this drawing is not based on any existing molecule. Upon consulting the book, it turned out to contain no further references to reality and consist only of the fantastical imaginings of the artist, so I won't make any further comment on this publication.

I could list more examples of artists that have attempted to employ molecular models, but in short all of these sculptures I've encountered forgone scientific accuracy in some way.
The only one I know of that isn't necessarily wrong was a sculpture that simply used nothing but a commercially available molecular modelling kit. So while this was possibly accurate, it's artistic value was also negligible.

And the reason I've written all this is because I researched the subject while making the following model of a molecule called methyl mercaptan:

Methyl mercaptan, or CH₃SH, is one of the molecules that make farts smell. This model is made of a tennis ball, a black golf ball and four small roulette balls. These generic, store bought, balls are both the right colour and approximately the right size for a CPK-model for a molecular structure, as can be seen in this rendering taken from a molecular drawing program:

This is thus an indication that it's possible to have a novel approach to creating a molecular model without necessarily having to significantly compromise its scientific accuracy.

On the Scale of Movements

 These are some screengrabs from a video of me doing a skateboard trick I learned recently. It's not a particularly impressive trick, it's just something I hadn't learned in the twenty years prior. When I sent  the video to a friend he said that I was 'making it look easy'.
And the reason he said that was that my arms were very low and close to my body the entire time.
Skateboarding is a perilous activity where you are constantly searching for balance, so mostly you instinctively spread your arms out to find your balance, like a tightrope walker. Yet if you notice my posture, and especially the position of my arms, you'll see my arms are barely raised above my waist the entire time.
I've got a tendency to do things with very restrained movements, and if you think about it for a second, that is exactly what you don't want to do in any activity that involves balance.

 This is a photograph of professional skateboarder Daan van der Linden, and he displays how you do want to position your body while skating. He has his arms wide open and up in the air, with his gaze firmly aimed to where he is going. This is a good and effective mechanism to control your balance.

Yet when I did my skateboard trick, I was effectively walking a tight-rope with the posture of a flaneur. If successful it can be said that this is 'making it look easy', but in reality I have a bit of a reputation of comedically tipping over more often and on simpler tricks than my peers. It can thus be said that generally speaking, skateboarding is an activity that favours large and rapid coordinated movements of the entire body over small inhibited movements of the extremities.

So, you might be wondering, what does this have to do with art?

In art, and particularly in painting, there is also a large difference in those who use restrained movements of wrists and fingers and those who employ larger movements of the arms. Naively this difference can be seen most easily in the existence of large paintings and small paintings.

In much of the common perception, a large painting equals a better painting. Many of the most famous artworks are also among the artists' largest works, like Rembrandt's Nightwatch and Picasso's Guernica. This is probably because art is priced by the meter and thus larger paintings are more expensive. And we all know expensive things are always of higher quality.
Yet in reality I know of very few painters whose work got better when they worked on a large scale.
Although the Nightwatch is Rembrandt's most famous work, it is a fairly unremarkable work in everything but its size.

 If we compare a self-portrait from 1669 with a similarly sized section of the Nightwatch, then the quality difference in the brushstrokes is difficult to ignore.
Large paintings often lack detail and precision, quite simply because it's difficult to perform at a high level for a long amount of time. For example, the average speed of the current world-record for the 100 meter dash is 10,43 m/s, while for the marathon it is 5,84 m/s.
And while stamina is an obvious actor in why large paintings tend to be of lower quality, I also think that a more restrained movement in painting is a very clear indicator of skill. When you think of skilled people, do you see them making large, flailing movements, or do they make small, precise ones? This is also reflected in colloquial uses of 'brute force' versus skill and intelligence.

As I pointed out at the beginning of this post, I'm a person who is very restrained in his movements. I believe this is reflected in the kinds of work I make, but also in the kinds of work I like to see. Much of large scale painting quite frankly has always looked brute and unsophisticated to me and very likely this is because I don't relate, on a personal level, to the the large movements they require. I myself don't move about that way in the world, so it's unappealing to me when other people do.

When I think of other artists whose technical skill I admire, they all seem to work from the fingers, rather than the arm. 

One of the most skilled painters I can think of is Wayne Thibaud. His work is also, usually, relatively small in size. Fortunately there is video footage of him at work available on the internet:

 
Notice how his brushwork is done with small movements of the wrists and fingers.
Contrast this with David Hockney, who is known for his large paintings. His movements are all from the arm. Even when drawing on a small iPad, he draws by holding his wrist straight and moving his arm.

Although there are minor differences in the methods of each artist, generally speaking movements of the fingers are associated with work on small details. And the work of Vija Celmins is probably as detailed as contemporary painting gets.

I also noticed that Jean-Michel Basquiat mostly paints with his wrist, which is interesting cause he tends to work on a large scale.

There is a quick back and forth movement you can only do with your wrist. To do this precisely with your lower arm, or even your full arm, is close to impossible. And because this style of painting technique magnifies a small movement into a larger one, it requires a lot of precision and muscle control, which isn't easy to imitate. This perhaps helps to explain the distinctiveness of his work, despite his many imitators.

The above footage is of Matt Connors at work. He's an artist with technical knowledge of paint and materials, but it's clear that the brushwork itself is almost unskilled. His brushwork is then done with the entire arm, with the hand itself barely moving. As these are large, relatively uncoordinated movements, anybody can learn how to make brushstrokes like this, which isn't necessarily true for the previously mentioned artists.

It's a shame there is not more material available on the physical movements that happen when artists apply paint. There is limited video footage and I've certainly never encountered any text on the subject. Yet it's the essential aspect where the artist quite literally creates the work.

I'm personally partial to restrained and precise movements, which tends to result in small, detailed work. Yet I'm also aware that as a person I move through the world in a much more minute manner than most. It is thus likely that many people don't relate to my way of doing, and instead prefer the more coarse doings of many others.

Some experiments

Towards the end of 2024 I performed some research on the chemical composition of a number of watercolour paints. In those experiments the mass fraction of the pigment was determined using UV-vis spectroscopy and thermogravimetric analysis in a number of paints with a quinacridone pigment. 

During that research I correlated some properties of the paint, such as sheen, to this mass fraction and the composition of the binder, which is gum Arabic. This in turn led me to make some predictions about their behaviour in water, which is the ultimate application of the paint.

In order to test these predictions, I devised a simple experiment where a small amount of dissolved watercolour paint was introduced with a brush to a small channel of water. Then it was merely a matter of observing the behaviour of the paint in the water.

Six watercolour paints with PV 19 pigment in water after 0, 15 and 60 minutes.

In the above image you can see the dissolution of six paints in water over time. From left to right they are arranged from low to high pigmentation. This also corresponds to a transition from large to small particles of gum Arabic.
As you can see, the smaller particles of gum Arabic, with higher pigmentation, generally dissolve faster and show more movement in the paint. It is however notable that the paint with the highest pigmentation and lowest particle size dissolves less fast than the other paints with high pigmentation. An explanation for this counter-intuitive observation is that the more tightly packed particles have less room for the water to enter and thus dissolve the paint.

Five Schminke Horadam watercolours in water after 0, 15 and 60 minutes.

I then repeated this experiment with five paints of the same brand, that I assume to posses a similar composition of paint. Their behaviour was indeed similar, while some small differences were still present. These can be explained by the differences in chemical composition of the various pigments, which will give different properties during the mixing and milling of the paint.

Winsor & Newton Professional (l) and Cotman (r) watercolour in water after 0, 15 and 60 minutes.

As a final experiment I tested if there was some validity to the observation that paints with a more matte appearance have larger gum Arabic particles and therefore dissolve more slowly. In the above image two paints from the same brand are tested. They are of different qualities, with the Cotman branded paint having less sheen than the Professional branded one. As it is clear to see, the professional branded paint, with higher sheen, did dissolve much more readily than the Cotman branded paint, which is an indication that the hypothesis might be correct. 

With these positive results, I then repeated these tests with a more common version of paper chromatography. The liquid phase in this instance is of course water.

From left to right; VG, RT, SCH, SCH', DS, DS', DS'' and KP

The first of these chromatography tests immediately produced some interesting results. The same paints are presented in the same order as in the first image. For the first three paints, we also see the same behaviour, where increased pigmentation and smaller particle size likewise give a further travel in the paper. It is then for the two highest pigmented paints that we see almost no travel at all. This was surprising so the experiment was repeated with the SCH and DS paints, to ensure that no kind of error was made while performing the experiment.
As this wasn't the case I can only assume that there is some kind of limit, whereafter the solubility of the paint in water is actually hindered by the paint particles being small enough to get 'stuck' in the fibres of the paper. So while smaller particles are generally are more easily brought into solution, there is probably some point where the paint particles are small enough to penetrate more deeply into the paper and then aren't removed as easily.

Winsor & Newton Cotman (l) and Professional (r) Permanent Rose

This is somewhat confirmed by the above experiment. Winsor & Newton paint was the slowest to dissolve in the first test and consequently they showed no travel at all in the paper chromatography experiment. This result is in line with the reasoning that larger particles of gum Arabic dissolve less quickly in water.

Schminke Horadam Mars Black, Mars Brown, Ochre, Lamp Black and Quinacridone Rose

A further test with the most soluble paint, Schminke Horadam, shows a near identical result as in the earlier tests. The explanations for this result are of course also similar to what we have already seen.

With the knowledge gained from these experiments in can therefore be said that paints with large particles of gum Arabic have generally lower pigmentation and dissolve less quickly in water. There is however a turning point when the paint is applied on paper, where smaller particles of gum Arabic attach more readily to the paper fibres and therefore adhere more strongly to the paper, hindering dissolution.

Storyboarding

 

When I document exhibitions, I attempt to illustrate the experience one has as a physical visitor with a body, walking through the space. Of course, this will always be at best be an approximation, but I nevertheless find this approach is more representative than the bulk of disembodied installation views one sees today. Those tend to highlight the individual qualities of the works or the space, but rarely provide an adequate sense of the spatial relationships between the works in the exhibition and therefore the exhibition as a whole.

As this walk-through is subtly different for every exhibition, I therefore document every exhibition like it's a new challenge to figure out how the relationships between the works can accurately be captured in photographs. In order to do this, I tend to make a number of photographs and figure out their order in the storyboard-like arrangements seen above. This arrangement usually makes it clear where there are gaps that need to be filled, or if the already taken photographs need to be adjusted in some way. 

Although this has been a very natural way of working for me that has proven to be effective in conveying the exhibitions at a distance, it nevertheless is something I have never seen anybody else do. But perhaps it's possible that I simply am not privy to the working methods of other photographers.

A Problem of Easily Tradable Objects

A traditional view of an artwork is that it's an easily commodified physical object. This object can then be displayed for its consumption and this display can in turn be done publicly in an exhibition. The exhibition is then the primary way for a larger public to engage with an artwork.
Indeed, we see that exhibitions are the most important aspect of an artist's professional life, even more so than creating artworks. This sentiment is reflected in the enduring popularity of texts like Boris Groys' The Politics of Installation, which was published fifteen years ago. Despite it being drivel about the 'sovereign character of artistic freedom', it is still regularly referred to today.

I've always strongly disagreed with the notion that the practice of exhibiting is a necessary condition for an artwork to exist, or function, and in the last few months I've thought about this issue in relation to some works I'm presently making.
In those works I feel like I'm presented with a problem of easily tradable objects that are nevertheless unsuitable for public exhibition.
I'm still very much in the process of figuring out such a seeming impossibility, as there are, quite naturally, very few examples of artworks that fit this description. The closest example I can think of is something like the works of Franz Erhard Walther, whose works require 'activation' by an audience. Yet this activation is pre-determined and nevertheless anticipates public exhibition of the works. So while there are some specific conditions for showing such a work, if those conditions are met, public exhibition is still very much an option without being detrimental to the work.

In my ruminations on the subject, I have noticed that public exhibition becomes difficult when multiple (physical) aspects of a work need to be simultaneously considered but aren't simultaneously available to a spectator. An example would be a situation where you have text that spans both sides of a piece of paper, while only one side is visible. 

This example of course has a easy solution in the form of a double sided frame. So please note that general problems of adequately displaying certain works are not what I'm concerned with here. I'm reminded of this atrocity of a display mechanism that was created for a print by Sigmar Polke:

The print was made on semi-transparent paper and presumably this set up was created to highlight this translucency. Although there is some difficulty in showing this property of the work, the difficulty would exist even if you could directly handle the work with your own hands. These kinds of obstacles are trivial and uninteresting, and are usually the result of an artist not considering how others can engage with their work.

No, the problem I'm thinking of is the kind where an object can be readily consumed and freely traded in the private sphere, but accurate communication of its core properties breaks down in a public setting due to the nature of those properties.
I have made some works where I believe something of the sort is going on and I would love to provide you with some documentation of them. Yet it's both fitting and ironic, as well as a minor proof of their inability to be publicly displayed, that I feel like I've been unable to photograph them in any way that captures this internal dichotomy. 

Addition on 30/11/2024:

 In the last month I've thought about this more and there are two artists who might relate to this concept further.

The first is Duchamp, who especially with his various boxes has created a number of objects whose status remains somewhat inscrutable. Those works are best suited for a private viewing where a single person goes through the work, like one would read a book. They carefully study page after page, and after a while the whole of the work is known to the observer. This is best done by handling the objects yourself, but it's simultaneously not impossible to show the work in full in a vitrine. It's more cumbersome to completely grasp the extent of the work if displayed in a more public way, but it remains accessible nonetheless.
Another aspect to note is that many of those works were made in large editions, which is commonly interpreted as undermining the importance of the original in art. This however ignores the fact that most of those works had a 'deluxe' edition, which included some kind of, even more, hand-crafted original object that was unique to that particular exemplar of the deluxe edition. Such an inclusion in an edition blurs the lines between what can be considered a 'unique' object, as this definition will shift depending on what you do or don't include in the artwork.

I'm also thinking of what is known as Eva Hesse's 'studiowork'. Those oddly shaped pieces of latex, wax, wire mesh and cheesecloth are perhaps best shown on a desk or some other kind of work area, like they were in Hesse's dwellings:

There the 'test pieces' appear at home and their position is immediately understandable. They have however since been shown at museums and galleries, where they appear more strange and out of place:

It's not that these works seize to function on a white plinth, but there is a definitive shift in how we are able to perceive them. Having known these works for more than a decade now, I'm however unable to talk about this change in perception in precise terms.

Dissolution Upon Contact With Water

When making some of the works from the γ-series, I noticed, or seemed to notice, that the watercolour was retained in the brush to a greater extent when using real sable hairs as opposed to synthetic materials. As this can influence the amount of control when has on the introduction of the watercolour to the droplet, I decided to test a number of different brushes.

For this experiment, a single batch was made of an unspecified amount of Royal Talens Rembrandt branded Quinacridone Violet (593) dissolved in 0,5 mL of distilled water.

Using a micropipette, a 5 µL droplet of distilled water was placed on Hahnemühle 290gms Agave watercolour paper.

Each brush was then dipped into the watercolour solution, rinsed two times by dipping it into distilled water and then placed into the droplet, as vertical as possible.

The action of adding the watercolour to the droplet was recorded by video. As the droplet had the tendency to move towards the brush, the first frame is recorded when the first movement of the droplet is observed, together with the frames 0,1 and 1 second after after this initial movement.

The following brushes were tested: Da Vinci Colineo, size 2/0; Da Vinci Fit Synthetics, size 0; Da Vinci Forte Synthetics, size 3/0; Escoda Perla Sintético, size 3/0; Gerstaecker, size 1; Winsor & Newton Synthetic Sable Round, size 00; Winsor & Newton Cotman 111 Round, size 00; Raphaël Martora Red Sable, size 3/0.

The experiment was repeated with Royal Talens Rembrandt branded Chromium Oxide Green (668). This colour consists of a simple inorganic pigment in the form of chromium(III) oxide, as opposed to the aromatic quinacridone pigment found in Quinacridone Violet.

This gave the following results:

Da Vinci Colineo, size 2/0

Da Vinci Fit Synthetics, size 0

Da Vinci Forte Synthetics, size 3/0

Escoda Perla Sintético, size 3/0

Gerstaecker, size 1

Winsor & Newton Synthetic Sable Round, size 00

Winsor & Newton Cotman 111 Round, size 00

Raphaël Martora Red Sable, size 3/0

An overview of all these tests gave the impression that the chromium oxide had more of a tendency to leave the brush than the quinacridone pigmented watercolour. The amounts also seemed to vary from brush to brush, with the additional remark that brushes of the same brand seemed to show similar diffusion.
Of these brushes the Escoda Perla Sintético brush had the least diffusion into the droplet. As this was also the most previously used brush, I wondered if this was perhaps related to the amount of use this particular brush has had. In order to find out, I bought an identical brush and redid the above test with both the new and the old brush:

Escoda Perla Sintético, size 3/0, used (top) and new (bottom)

In addition to the Quinacridone Violet and Chromium(III) oxide, I also used Royal Talens Permanent Lemon Yellow (254), which consist of bismuth vanadate.
There was very little difference between the new and the old brush. Perhaps the older brush had slightly more diffusion than the newer brush, but this can't be said with any certainty.

Another noteworthy observation is that the Quinacridone Violet didn't seem to dissolve into the droplet at all from the Gerstaecker branded brush.
Additionally, the only brush that contains the much-coveted real sable hair, the Raphaël Martora Red Sable, has a very different diffusion pattern from all the other brushes. The hairs of the brush spread far more easily than those in any of other, synthetic, brushers.

Related to this is the observation that the water in the droplet is very much attracted to the water present in the brush. This attraction is so strong that with a minimal amount of water, the droplet is almost 'sucking' the water out of the brush:

Testing, Testing.

Recently I wrote about some watercolours I've made. Since then I've found some scientific literature on the subject, after discovering that the 'coffee ring effect' is the scientific name of a ring shaped deposit found after a drop of liquid has dried. It's a relatively new field of study, with major research only being done since the late 1990's. This literature does confirm my basic assumption of the movement of the paint particles, which is explained by capillary flow. The literature also shows that there are many competing phenomena and variables at play, which are difficult to measure and analyse. Many of the papers I found focus on variables like temperature, relative humidity and electromagnetic influences, most of which effect the rate of evaporation.

I've done some experiments to test the influence of some of these parameters on the appearance of my own drops of watercolour, with some notable results.

First I tried to measure the influence of temperature. The results of this were mostly inconclusive. To test the influence of temperature, I uniformly applied the droplets at three different temperatures, to see if their appearance would differ after drying. The expected result from some of the literature would be that a higher temperature creates a more even distribution throughout the drying droplet. Various mechanisms have been suggested on how this works, including a greater evaporation at the contact surface with the air, which causes greater flow inside the droplet, as well as a 'surface capture' effect of particles at the contact surface.
In the rudimentary testing I have done I however didn't notice any significant effects of temperature on how uniformly the paint spread through the drying droplet:

Three drops dried at different temperatures

In this image there are three droplets of about 2 mm in diameter, made with Winsor and Newton's Payne's grey watercolour paint. The first was made on a substrate that's cooled below 0ºC, the middle was made at room temperature and the last one was heated after application in an oven to about 70ºC. It's clear that there is little significant variation between these three droplets, thereby giving indication that temperature, at least on this scale and with these materials, is not a significant contributing factor for the distribution of the pigments in the drying droplet.
However, the influence of temperature might be dependent on the exact chemical composition of the pigments, in combination with corresponding changes in the binders used. The following image consists of the results of the same experiment, showing Daniel Smith's Hematite Genuine watercolour paint, in duplicate, at <0ºC, room temperature and ~70ºC, respectively.

Two sets of three drops dried at different temperatures

What one can observe here is greater ring formation with a cooled substrate and more concentration at the center at elevated temperatures. So much so that the ring where the pigment is deposited is not even found at the outer edge of the droplet, which is something I have not observed in other situations. This behaviour is also the exact opposite of what the literature would have us expect.

When examining the literature, it must also be noted that most of the literature on the coffee ring effect seeks to eliminate it, because in an analytical or manufacturing context its existence is commonly detrimental to achieving uniform depositions or measurements. Relatively little literature thus exists on controlling the formation of the ring itself, and as far as I can tell, all research is done on colloids that are mixed prior to droplet formation. Little to no research has been done on the effects of introducing a colloid to an existing droplet. Yet I've found indications that for our purposes this provides a lot of control on the exact formation of the coffee ring, as can be seen in the following image:

Four different ways of introducing the paint

From left to right, this is a simple droplet of a diluted suspension of Winsor and Newton Payne's grey watercolour, a water droplet to which a diluted suspension was added at the centre point of the droplet after droplet formation, a water droplet to which a diluted suspension was added at the right edge of the droplet after droplet formation and a water droplet to which a near-saturated suspension was added at the right edge of the droplet after droplet formation.
As you can see, the two leftmost droplets dried nearly identical, even if their method of application was very different. For the third droplet from the left, paint was added later at an angle on the right edge with the paper, and this saw most of the pigment end up around the full perimeter of the droplet. This process was repeated with a higher concentration of pigment in the last droplet and while this contained far more pigment than the other three droplets, still most of it stayed at the perimeter of the droplet, with even more seemingly remaining at the initial point of introduction.

My explanation for this is that a similar outward pushing effect is at work here, inhibiting the possibility for pigments to enter the centre of the droplet through gravity or other forces.
It must however be also noted that in some degree this is dependent on the exact shape of the droplet and again the composition of the paint.

Three different ways of introducing the paint

In this image we have a droplet with a homogenous solution of Daniel Smith's Venetian Red water colour paint, followed by a saturated solution of the same paint added at the right edge of a droplet of water and ultimately a heavily diluted solution added at the right edge of a droplet of water. They each have their distinctive appearances, which differ subtly from the previous experiment with Payne's grey, most notably with the later introduction of a saturated solution. This produced a light centre with a thick edge in the previous experiment, while it created a mostly even spread with a thin edge in the latter example.

Even though it's difficult to observe this behaviour in real time and at actual scale, I believe the observations from the previous two figures is related to the behaviour of the pigment at the droplet's contact surface with air. I did a test where I placed a small saturated spot of Payne's grey watercolour on a piece of paper, let it dry, and then added a water droplet, without physically disturbing the spot of paint. What I found after this droplet had dried is that the paint had spread uniformly throughout the droplet, with a clear coffee ring effect present. There thus is a tendency for the paint to be distributed inside the droplet if it gets far enough inside. 

Adding water to a dried spot of paint

Generally speaking, predicting the exact behaviour of the interaction of a fluid and a colloid is complex and very difficult, as can be seen in the following example:

Introducing two paints into a single droplet

In this image two different watercolour paints are added to a single droplet. The droplet at the top was a diluted solution of Daniel Smith's Quinacridone Gold water colour paint, to which a saturated solution of Daniel Smith's Quinacridone Red was added on the right side at an angle. The droplet at the bottom was pure water, to which Quinacridone Gold was first added at the top and then Quinacridone Red was added on the right side at an angle. As is clearly visible, the latter process resulted in a nearly homogenous mixture, while the first gave a degree of separation between in the colours in the dried droplet.
However, I then repeated this experiment using Daniel Smith's Quinacridone Gold and Winsor & Newton's Payne's grey.

Introducing two paints into a single droplet

Here the same procedure was followed, with the Payne's Gray being added first, followed by Quincridone Gold on the right side at an angle. The way the paints mixed was the opposite of what I observed in the previous experiment. On this occasion the Quinacridone Gold mixed better with the droplet of diluted water colour, while the two paints stayed separated when added in sequence to a droplet of pure water. At the present time I have no simple explanation for this seeming contradiction in behaviour.

Lastly I want to note another characteristic I hadn't considered up until this point, which is the influence of magnetic effects on the droplets. Naturally electromagnetic effects are strong if there are ferromagnetic pigments present in the paint. Especially in the case of paints that contain a mixture of magnetic and non-magnetic pigments, introducing a magnetic field during the drying process produces interesting effects that can be easily controlled with the presence of any magnetic field. 

In conclusion, about a month has past since the previous post and I have still made some new observations about the behaviour of the watercolour paint inside a droplet. Some of these observations seemingly contradict the explanations found in current scientific literature, while others provide a possibility for new methods that are hitherto unexplored.