These essays are published on the website  'Being Here - Witnessed Presence - Work in Progress' (under the tab Artists/Carlgren), and in the books Witnessing You, On Trust and Truth in a Networked World and Witnessing You, Artistic research into being and bearing witness in a networked world. Delft: Participatory Systems Initiative Delft University of Technology, 2012.

Looking through glass

Glass is fundamental to witnessing; it changes our experience of the world and of each other. Glass plays a significant role in modern society and is as a carrier of information an indispensable material in human interaction and communication. Much of the information conveyed between humans reaches us through glass, and we stay connected through glass fibre cables and computer monitors. Glass is an essential component in telescopes, microscopes and so many other interfaces and consequently it is seen as a tool. Glass in fact deeply affects what we see and therefore what we think. Glass changed how people live by giving shelter, providing speed, vision, transport and recently Internet and Mobile Interfaces for communication. What is it that glass actually does, what is glass?

Interpreted transparency: Do you see what I see?

My fascination with glass started, at the age of eight, when I got my first pair of glasses. What a fantastic tool. Suddenly I was able to see clearly, and read!

The notion that the shape of things could be altered by altering the angle of the frame while looking through the glass was an amazing discovery. I had a lot of fun with my new toy, through which I could make my teacher pull faces and look funny. At the time I had of course no idea of how, or why. Now I know that I had stumbled on the optical power of glass.

My daughter teasing me on my birthday: One candle on the cake+these goggles=See how old you are Mum!

Public space needs different visual disruptions


The unique optical properties of glass induce witnessing and make public space alive and visual. Optical phenomena can make an area vibrant, give people a feeling of how to position themselves and, through its unique properties, transform empty space into public space.

     Living Light by Mathijs van Manen, installed at VRIJ GLAS, January 2008.

Optical Phenomena as Architectonic Elements
In my work the main facets are light refraction, how it originates and its influence on the human eye. My foremost interest is how light diverts as it passes through glass. I combine my sculptural work with research on new uses of glass in structural design, focusing on the optical properties of glass, the phenomena of light and refraction of light and how it is transmitted through glass and its possible integration in architecture. It is my belief that public spaces need different visual disruptions without the loss of existing light for new types of experiences of space.

Witnessing: Multifaceted glasses

With my work I want to demonstrate how minimal alterations can have a monumental effect and that with the help of glass it is possible to influence what the viewers see. Multifaceted glasses can show us things we otherwise would never see or experience.

Faceted glass can move images and block view, by Anna Carlgren.

Reversed, scaled-up and integrated in a window, by-passers will see the ceiling, nothing more.

In the 17th century multifaceted spectacles were often part of art cabinets and art chambers, a princely fashion in those days for royalty and aristocracy who collected art and objects of different types as a manifestation of their culture, education and wealth. Eminently present in such collections of oddities is the desire for discovery, the joy of collecting, and possessing treasures.

Art cabinet made in Augsburg, Germany 1625-1631. It is filled with thousands of wonderful, odd artifacts and permanently on display at Uppsala University in Sweden.

Witnessed witness: Altering thickness of glass affects perception

Curved or angled glass allows the viewer to see sometimes less, sometimes more. By changing the thickness of the glass images can be multiplied and moved. Below is a picture of a person photographed through a glass window that has prisms mounted on its surface. The metamorphose takes place on both sides of the glass window. The only way to find out what the other person is seeing is if a photograph is taken of what is being witnessed on the other side of the glass. The degree to which an image is scrambled depends on the distance between the viewers and their distances to the glass.

    Prism puzzle 60x60 cm by Anna Carlgren.

Glass refracts light. We have known this since time immemorial. Cut and polished gems also have this property. In my home country Sweden cut crystal is generally associated with large and heavy glass bowls or with gilded chandeliers. I want to approach cut and polished glass from a different
dimension. Bold experimentation, producing constellations of forms that are very carefully calculated, reveal completely new aspects of the refractive capabilities of glass. I often take cast blocks of glass as my point of departure, but I also make use of window glass, which I cut into pieces, grind and polish. I do not want any of this laborious work to be seen in the finished pieces, the light and its refractions makes the work alive.

World upside down

When looking at this picture at least three convex lenses are involved. In the human eye (1), in the glass (2), and in the camera (3) that captured the photo. They all have the ability to turn the world upside down. Images of the world, as we see it (provided no extra lens is involved) enter the human eye inverted. In a camera the images are also captured upside down on the film, and when using a large format camera the photographer even previews the images inverted. That the images are captured upside down on the film does not matter; nothing could be easier than turning a negative. The lens in my glass piece below works accordingly. We humans have an advantage; our brain turns the images around for us. In my piece, the centre image actually hits the retina (the light-sensitive tissue lining the inner surface of the eye) right side up. In this case, it is the viewer's brain that turns the world up side down.

    World upside down, a perceptible illusion 200x100 cm by Anna Carlgren. Photo: Wyke Valkema

Glass has this wonderful ability of being able to alter things. Solely by changing the thickness of the glass different optical phenomena and optical effects occur. The piece 'World upside down' show convergence through a convex lens. The term convex denotes a surface like the outside of a ball or sphere and convergence is the bending of light rays towards each other by a convex lens. Both the lens and the window should be made of the same type of glass to ensure the same coefficient of thermal expansion.

Floating head: This is real!

A head takes off into the air. This is really happening. The image has not been manipulated; the photograph is a true record of what in real time is perceptible to the eye (or the camera) through the glass. Variation of the thickness of the material is the sole component responsible for recorded observations. A graphic designer can bring about the same with photo editing software in a desktop publishing program, but then it all goes on at the computer screen. I leave that process to the material. In my Floating head you can (to everyone's great delight) both laugh and wave at the same time as your head goes up in the air.


Floating head by Anna Carlgren, 90x195 cm.

Outdoor sculpture: Do you see what I see?

Visitors almost always want to change places with each other. They signal and yell to each other through the glass "Do you see what I see?" What they see, as with most optical phenomena, is dependent on the distance from the observer to the refractive or reflecting material and the distance from that material to the witnessed presence.

Optical sculpture by Anna Carlgren

 Modern flat glass


Versatile and innovative use of glass at home and in public space will in the future provide for many new developments like possibilities for reading email in the bathroom mirror while brushing your teeth. We will have no more post-it notes on the fridge; the door is a computer screen with a To Do List and pictures of Grand-ma. The radiators under the windows will be gone because the windows heat the rooms, and instead of curtains the windows themselves can block the view with the flick of a switch. That same window can be your television and film projection screen; it can also act as an alarm clock that mimics sunrise like a natural daylight lamp. Photo-chromatic car glass windows gradually darken in bright light and vice versa. Transparent windows double as solar panels, information panes for public transport can automatically detect and change to a language that the viewers can understand (a great service for tourists). It is all about light, electricity and heat conductivity. I see function, though I lack aesthetics and I also miss the human scale.


Serie Parallel-Prisma by Durk Valkema

Modern flat glass is green, the thicker the greener. From some manufacturers it has a slightly more bluish hue, while other glass can be slightly greyish. Looking at the colour is the only way one can distinguish glass from one source to another. Glass is seldom marked with the producer's logo. Float
glass is poured hot on a bed of liquid tin, left to float to a flat surface, hence the term float-glass. Traces of tin are left on the surface of the glass. Special tools can detect which side of the glass was on the molten metal during production, relevant information in some applications. Bulletproof and
soundproof glass consists of layers of glass and plastic foil. How flat the glass is determines what we see, as does the refractive index of a material. (Think of how a pencil in a glass of water looks as though it is bent.)

In his work Durk Valkema makes use of the fact that a layer in between the glass (foil or glue) has a different refractive index than glass.

The refractive index for air differs from that of a vacuum, water or glass. How fast the light travels through a substance also depends on the thickness of that specific body, factors that effect refraction. Refractive index, or index of refraction, can be defined as follows: light travels through space as a wave with amplitude, wavelength and speed that is dependant upon how it was emitted and the medium through which it propagates. The velocity of light within the medium where the light travels is known as index of refraction.

Handmade window glass


Handmade window glass is used when something extraordinary is required, for example in restorations and art projects. Architect I.M. Pei did not like to use ordinary green glass for the glass pyramids at the Louvre in Paris. Glass with less iron (a colouring impurity) was specially melted for the purpose and poured into great slabs. After cooling the slabs were then cut and polished on both sides. The exact same method was used to make the mirrors for 'Galerie des Glace' at Château des Versailles several hundred years preceding.

Example of handmade colourless window glass, used by I.M. Pei.

Galerie  des Glace, Château des Versailles, France.

Handmade window glass with irregularities that originate from production form a kind of cylindrical lens; light is dispersed, light influx is not affected.

Antique handmade window glass.

Unbreakable glass

Truly unbreakable glass would be a dream come true since all mobile devices depend on glass. In 1962 Corning Incorporated invented a method of making strong ultra thin flat glass. The Corning Museum of Glass has a model on display showing the process of how a thin film of molten glass merges with another not touching any surface in the process, as is the case in other flat glass manufacturing. At the time Corning did not know for what it could be used. Almost fifty years later they showed this innovation to one of the worlds largest manufacturer of electronic devices and since then it is widely used in mobile telephones. Below an ancient anecdote about unbreakable glass and why the Internet has its own proposed Saint.

Already two thousand years ago man had set out to make unbreakable glass. According to a legend taken down by the archbishop Isadore of Seville the Roman emperor Tiberius Caesar was presented a vessel made of unbreakable glass. Writers at the time called it 'vitrum flexile' or flexible glass. As Caesar threw the cup to the floor it did not shatter. When questioned, the inventor swore to the emperor that only he knew how it was made. Whereupon Caesar had the man beheaded, and his workshop destroyed, fearing such a material would undermine the value of silver and gold. Nobody can say if that glassmaker had made some kind of shockproof glass avant la lettre.

Here is what The Corning Museum of Glass says about this story: "Some think that vitrium flexile was merely describing "bent" glass, and that the man had designed some new style of hollow-handled vessel. However more than this would have been needed to impress the Roman establishment, used as it was to vessels of great intricacy. A better explanation would seem to be that the glass worker really had stumbled upon a primitive kind of shock-resistant glass. (Note by CMOG: Perhaps this is just a tale; it doesn't have to be true!)

Ordinary glass is based on silicon dioxide (sand), sodium carbonate (soda) and calcium carbonate (limestone), a type of glass often called soda-lime glass. To modify glass into relative unbreakability requires a radical change to the formulation. The essential new ingredient is a few percent of boric oxide. So could our unknown glassmaker have had access to either boric acid or borax, both of which occur naturally?

In the Middle Ages borax was regularly imported into Europe from the East to be used as a flux by goldsmiths. It came from the remote regions of Tibet. Could a little have found its way to ancient Rome 1500 years earlier? Maybe. There was a flourishing trade in those days between the Roman Empire and the Indian sub-continent. If so, our glassmaker may have bought some borax and noted its remarkable effect when added to the glass batch.

However there were two potential sources much nearer home. The steam vents of the Tuscan Maremma north of Rome, contained natural boric acid. Geologists did not establish this fact until the 1820's, but it is surely possible that our ill-fated glassmaker came upon some unusual looking crystal salts in a dried-up Tuscan pool and decided to see if they had any effect on glass. The Romans possessed even richer sources of borates elsewhere within the Empire - in (what is now called) Turkey. These, too, were unknown until the nineteenth century, but again it is possible that boron-containing material from north-west Anatolia (modern Turkey) found its way into the glassmaker's batch - mistaken, perhaps, for some form of silica.

Boron has the wonderful gift of being able to change the number of chemical bonds it can make. The boron-oxygen bond is itself astonishing strong, but true boric oxide can make only three bonds. However, if more oxygen is added - sodium oxide, for example - it can make four bonds. This imparts great three-dimensional strength. Add the compound to a formulation and the response to thermal shock of the resulting glass is crucially improved. It becomes heat-resistant, oven proof, and can be used for cooking, chemical apparatus, thermometers, telescopes, and a hundred other functions. The strong bonding also increases resistance to water and chemicals, so boron containing glasses are ideal for medical ampoules, laboratory instruments, floor and wall tile, even kitchen sinks."

The glass manufacturer Corning Incorporated has come close to making unbreakable glass, here is what they reveal about the process of making Gorilla Glass as they call it: "The glass is placed in a hot bath of molten salt at a temperature of approximately 400°C. Smaller sodium ions leave the glass, and larger potassium ions from the salt bath replace them. These larger ions take up more room and are pressed together when the glass cools, producing a layer of compressive stress on the surface of the glass. The special composition of Gorilla Glass enables the potassium ions to diffuse far into the surface, creating high compressive stress deep into the glass. This layer of compression creates a surface that is more resistant to damage from everyday use." And, Asahi Glass, Japan's largest glass maker, announced in January 2011 a super-tough, scratch resistant cover for gadgets that it says is six times stronger than a conventional glass, they call their glass Dragontrail. The product represents Asahi's intensified ambitions to grab a chunk of the surging global market for smartphones and tablets. All those devices need a durable sheath to protect what's inside from the bumps, nicks and falls that inevitably come with use. (Source:

Thinking back to the unfortunate glassmaker two thousand years ago, I wonder if it is just an anecdote. Our literary man, the blessed archbishop Isadore de Seville, who wrote about unbreakable glass in Roman time, is Proposed Patron Saint of Internet Users.

Thinking back of the unfortunate glassmaker two thousand years ago I wonder if it is just an anecdote. Our literary man, the blessed archbishop Isadore de Seville, who wrote about unbreakable glass in Roman time, is Proposed Patron Saint of Internet Users.

Building blocks change direction of light


Glass is a useful and versatile material, unbeatable when there is a need to force light to go around the corner. Imagine bringing natural day-light to windowless rooms, for ever. The beauty of it is that by turning the blocks, 90 or 180 degrees the light will go this, or that, direction. Same principle at work as described in the other articles here about optical phenomena in architecture. Vary the thickness of the glass, et voilà!

Molten glass poured in cast iron moulds (nice orange because still hot) in production at VRIJ GLAS in Zaandam, NL.

When light travels from the sun to the earth, the medium in which it travels is mostly empty space. When light travels through an optical tool the principal media are air, glass and then air again before the light hits the eye. Glass can, depending on its shape, thickness, and index of refraction transmit light in a totally different direction than it had entered, a principle that is used in these building blocks. These objects are carefully designed to allow natural light to flow into windowless spaces.

Compare the effect of a 60W lamp with the light from only two rows of building blocks mounted in a patio above; it is as if the whole room is tilted towards the sun.

Prismatic glass transmit and (re-)direct light

Light passes through glass mostly in one direction. Prismatic glass can direct light in a certain, pre-calculated, direction. Turning the glass makes the light go in another direction, a useful feature when wanting to create an evenly lit room.

Prismatic glass, used by H.P. Berlage, recreated by VRIJ GLAS, Zaandam, NL.

Sheets of prismatic glass bend light according to the same principle as in building blocks (previous article) and can light cabinets and bring light to rooms shut off from daylight while also blocking people's view. The Dutch architect H.P. Berlage used this glass for exactly that reason. He wanted to give light to paintings and thought that they should be lit evenly on all walls. This glass has the ability to direct light and depending on how the panels are set all the incoming light will go in a certain direction. In the original design of the Municipal museum in The Hague the entire ceiling was made of prismatic glass, though most of the glass was destroyed during the bombardments in the Second World War. The Vrij Glas foundation recreated this prismatic glass for the renovation of the museum.

Kaleidoscope: Engaging the eyes


How a graphic pattern cut in safety glass can draw forth a smile.

In our day-to-day lives most of us normally don't particularly notice the glass that surrounds us. Ever since the first window was mounted in the wall of a house, humans have been happy being protected from weather and wind, and glad to be able to work inside in daylight. Glass is a useful, practical and strong material, although sometimes glass is referred to and seen as being an obstacle, a barrier. Through introducing elements, which to the eye is seen as real, while the brain consciously knows it to be impossible, the viewers see things differently from what they are, or appear to be.

Kaleidoscope by Anna Carlgren, 50x50 cm. Photo: Anders Qwarnström

Kaleidoscope by Anna Carlgren, cut in a window made of safety glass, 100x200 cm.

By varying the thickness of the glass in a regular pattern a kaleidoscope appears. Changing mass is all that is necessary to produce a kaleidoscope in an ordinary window. The shape of the refracting material, the thickness, and the index of refraction are the three things that determine the focal length of each optical phenomenon and by that what is perceptible to the eye.

C'est impossible ça! It's impossible! Kaleidoscope by Anna Carlgren 100x200 cm. Resulting in intense eyes wanting to know more. Engaging the eyes.

Trompe l'oeil, deceiving the eye

When exploring optical phenomena many test pieces need to be fabricated. Some can elevate the eye like a periscope, another lets you see around the corner or both, and a different combination might allow you see through walls. Finding tools that can deceive the human senses and allow for translation to a larger scale is the intent.

1: any state or process known through the senses rather than by intuition or reasoning 2: a remarkable development (source: Princeton University)
entry: phenomenon
part of speech: noun
definition: wonder
synonyms: abnormality, actuality, anomaly, appearance, aspect, circumstance, curiosity, episode, event, exception, experience, fact, happening, incident, marvel, miracle, nonpareil, paradox, peculiarity, portent, prodigy, rara avis, rarity, reality, sensation, sight, something else, spectacle, stunner, uniqueness

Always out of focus. Why?

Raindrops refract light. A double rainbow is perceptible when a double refraction occurs in the drops; in the second one the colours appear in reverse order.

Light refracted by a cut and polished glass prism. Prism: 8x4x3cm. Spectrum on the wall: 80x20cm. The background wall is white in reality. The light is extremely bright. The camera overcompensates.

Trying to capture the vibrant colours of a rainbow is utterly difficult. It does not seem to matter how the camera is set. A camera cannot register how a prism refracts the light and what I see. I get the same result over and over again, a rainbow out of focus.
The bow does not have a specific place; it has only a direction - like the wind.

I can see it, but where is it?

A prism integrated in a window across the room throws a rainbow every time the sun is shining. (Champagne glasses by Ulla Forsell)

Glass prism by Anna Carlgren

Why is glass transparent?


Professor Philip Moriarty, University of Nottingham, is shedding light on the difference between opaque and transparent materials.

Rain on glass (each drop is a little lens).

Professor Philip Moriarty studies nanoparticles at the University of Nottingham, and explains in this short movie, the difference between an opaque and a transparent material:

Astronomer Dr. Amanda Bauer who researches galaxy formation talks about photons and as a quite wonderful extra little surprise, she will also speak about why the sky is blue during the day and orange/red during sunrise and sunset:

(FlashPlayer is required)

This lens window by Anna Carlgren shows how light sometimes bounces off completely transparent glass, and sometimes not. Photo: Wyke Valkema

This window by Anna Carlgren is 100x200 cm. The picture shows how completely transparent glass not always allows the viewer to see what is on the other side. To find new and innovative applications for glass in architecture further research is necessary.

The nature of glass remains anything but clear

by Kenneth Chang


It is well known that panes of stained glass in old European churches are thicker at the bottom because glass is a slow-moving liquid that flows downward over centuries. Well known, but wrong. Medieval stained glass makers were simply unable to make perfect flat panels, and the windows were just as unevenly thick when new.

Most of the glass in Saint Chapelle, 4 Boulevard du Palais, Paris 4eme, is original and dates back to 1246-1248. (That is more than 760 years ago!)

The tale contains a grain of truth about glass resembling a liquid, however. The arrangement of atoms and molecules in glass is indistinguishable from that of a liquid. But how can a liquid be as strikingly hard as glass?
"They are the thickest and gooiest of liquids and the most disordered and structureless of rigid solids," said Peter Harrowell, a professor of chemistry at the University of Sydney in Australia, speaking of glasses, which can be formed from different raw materials. "They sit right at this really profound sort of puzzle."
Philip W. Anderson, a Nobel-prize winning physicist at Princeton, wrote in 1955: "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition."
He added, "This could be the next breakthrough in the coming decade."
Thirteen years later, scientists still disagree with some vehemence, about the nature of glass.
Peter G. Wolynes, a professor of chemistry at the University of California, San Diego, thinks he essentially solved the glass problem two decades ago based on ideas of what glass would look like if cooled infinitely slowly. “I think we have a very good constructive theory of that these days,” Dr. Wolynes said. “Many people tell me this is very contentious. I disagree violently with them.”
Others, like Juan P. Garrahan, professor of physics at the University of Nottingham in England, and David Chandler, professor of chemistry at the University of California, Berkeley, have taken a different approach and are as certain that they are on the right track.
“It surprises most people that we still don’t understand this,” said David R. Reichman, a professor of chemistry at Columbia, who takes yet another approach to the glass problem. “We don’t understand why glass should be a solid and how it forms.”
Dr. Reichman said of Dr. Wolynes’s theory, “I think a lot of the elements in it are correct,” but he said it was not a complete picture. Theorists are drawn to the problem, Dr. Reichman said, “because we think it’s not solved yet — except for Peter maybe.”
Scientists are slowly accumulating more clues. A few years ago, experiments and computer simulations revealed something unexpected: as molten glass cools, the molecules do not slow down uniformly. Some areas jam rigid first while in other regions the molecules continue to skitter around in a liquid-like fashion. More strangely, the fast-moving regions look no different from the slow-moving ones.
Meanwhile, computer simulations have become sophisticated and large enough to provide additional insights, and yet more theories have been proffered to explain glasses.
David A. Weitz, a physics professor at Harvard, joked, “There are more theories of the glass transition than there are theorists who propose them.” Dr. Weitz performs experiments using tiny particles suspended in liquids to mimic the behaviour of glass, and he ducks out of the theoretical battles. “It just can get so controversial and so many loud arguments, and I don’t want to get involved with that myself.”
For scientists, glass is not just the glass of windows and jars, made of silica, sodium carbonate and calcium oxide. Rather, a glass is any solid in which the molecules are jumbled randomly. Many plastics like polycarbonate are glasses, as are many ceramics.
Understanding glass would not just solve a longstanding fundamental (and arguably Nobel-worthy) problem and perhaps lead to better glasses. That knowledge might benefit drug makers, for instance. Certain drugs, if they could be made in a stable glass structure instead of a crystalline form, would dissolve more quickly, allowing them to be taken orally instead of being injected. The tools and techniques applied to glass might also provide headway on other problems, in material science, biology and other fields, that look at general properties that arise out of many disordered interactions.
“A glass is an example, probably the simplest example, of the truly complex,” Dr. Harrowell, the University of Sydney professor, said. In liquids, molecules jiggle around along random, jumbled paths. When cooled, a liquid either freezes, as water does into ice, or it does not freeze and forms a glass instead.
In freezing to a conventional solid, a liquid undergoes a so-called phase transition; the molecules line up next to and on top of one another in a simple, neat crystal pattern. When a liquid solidifies into a glass, this organised stacking is nowhere to be found. Instead, the molecules just move slower and slower and slower, until they are effectively not moving at all, trapped in a strange state between liquid and solid.
Read the rest of the article by Kenneth Chang, published July 29, 2008 in The New York Times:

Main glass ingredients: sand / soda / limestone

 70% Silica (sand) SiO2, 18% Sodium oxide (soda ash) Na2O, 12% Calcium carbonate (lime) CaO melted at around 1320 degrees Celsius makes a typical glass which can be formed by blowing by mouth or machine, by casting, by pressing and by drawing.

While casting a glass lens the temperature of the glass is approx. 1120°C, after proper cooling the lens will be cut and polished.

Sand is the major glass forming component and sand of good enough quality is found in many parts of the world. Glass sand should not be too coarse and not too fine and should not contain more than 0,03% iron oxide FeO3 unless to make a green or brown glass where iron is a key colouring agent. Soda lowers the melting temperature of silica and act as a refining agent, while calcium is a stabiliser. A typical source for calcium carbonate is natural limestone, dolomite or marble, providing it contains less than 5-15% magnesium oxide MgO. Aluminium oxide Al2O3 is often a component in calcium rich dolomite. All traces of metal oxides and minerals must be accounted for in calculating a proper batch formula.

All ingredients are thoroughly mixed together before being charged in a clay pot in the hot furnace and left to melt for at least 8 hours.

Next day: a refined melt. Karel Wasch said about glass that it is the only material that is purified through purgatory.

Experiment I: glass flowing at room temperature


Is glass a liquid or a solid? Experts do not agree on this one. Some argue that glass is an under-cooled liquid and not a solid, because solids have a definite melting point. Here an experiment that I am conducting since the spring of 2011.
Set-up: 15 February 2011
Within 24 months I want to be able to measure a change.


Ice melts at zero degree Celsius, silver 962°C, gold 1064°C and iron 1535°C. At melting temperature solid materials suddenly go from solid state to a liquid with no in-between state. Glass does not have one defined melting point. If you heat a piece of glass it will start to become soft enough to take a dent around 500 degrees Celsius. Heat some more and with a pair of tweezers you will be able to draw a thread. Further heating will make the glass begin to flow and at really high temperatures like 1400-1500°C or more it will flow and be fluid like thin syrup. Is the fact that glass does not have a specific melting point proof enough that glass is a liquid? The argument is that liquids flow and over time, even a super-cool amorphous solid like glass will flow. Let us see if it can be proven. Here is an experiment that I have never tried before: Two supports horizontally lined, and a meter apart, will hold a straight glass tube. It initially sags a bit because of its elasticity but flexes back when I lift it off. It will now sit there, lowest point marked, for say 18-24 months so that we can find out if it has sagged further and if it then will keep its curve. If it is a liquid it may maybe flow to a new shape. If so, the longer the tube is left the more it will flow. I hope to witness a result within a set period.

Experiment with a 0,8 cm glass tube, 140 cm long: Can glass flow at room temperature?

Experiment II: dissolving glass in water

Set-up on 22 February 2011: an empty jar, weighed without lid, filled with distilled water. After 24 months I will empty and clean the jar and weigh it again, to find out if some of the solid glass mass has been dissolved.

Can glass really be dissolved?
Some experts argue that glass is a mixture, or as they sometimes say, a solution. Glass does not have one definite chemical composition; all manufacturers use their own secret formula. The ingredients are melted and stirred until they are dissolved, and then cooled. Sand is the most important ingredient in glassmaking. To make clear, colourless glass the sand should not contain a lot of impurities like iron, which gives a distinct green tint to the finished products. To make glass for optical purposes pure silica is the main ingredient. Other ingredients can be calcium oxide, boron oxide, potassium oxide, sodium oxide, zinc oxide, manganese oxide, lead oxide, arsenic oxide, and many other components which when they melt together with silica form metallic silicates. Chemical stability is one of the most important qualities of glass, as air contains moisture and exhausts fumes. Moisture condenses on glass, absorbs carbon dioxide and form carbonic acid. In chemical laboratories pure distilled water is kept in bottles made from a special type of glass because distilled water will dissolve ordinary glass.

The periodic table of elements


Glass plays a significant role in modern society and glass is as carrier of information an indispensable material in human interaction and communication. Much of the information conveyed between humans reaches us through glass, and we stay connected through glass fiber cables and computer monitors.

In my work I focus on the optical properties of glass, the phenomena of light and refraction of light as it is transmitted through materia. Through my sculptural work I am able to experiment with glass in a way that furthers my discourse on light refraction, how it originates and its influence on the human eye. The purpose is to find ways to translate my findings to an architectural scale, for which I have developed the series Optical Phenomena as Architectonic Elements.

This research project is generously supported by The Swedish Arts Grants Committee, and previously also by The Swedish Royal Academy for the Arts and Cité Internationale des Arts in Paris.

Winged sculpture by Anna Carlgren (the prism allows you see around the corner, a principle used in binoculars to bring the image from the view pieces to the eyes)

Atomic green by Anna Carlgren (UV-sensitive glass, uranium oxide is the colouring agent)

Portrait of my daughter, or You are my rose bud by Anna Carlgren (rose with gold leaf applied hot, stem painted with gold lustre and fired)

Cut Iceland Spar by Anna Carlgren (crystallized calcium carbonate gives double refraction)

Verre à la façon de Venise by Anna Carlgren (Venetian techniques in stem and foot) -STOLEN-IF FOUND, DO NOT BUY OR RESELL

Time-less is more by Anna Carlgren (Roman foot, one long glass thread forms the foot)

Red rosette by Anna Carlgren (cleaved optical glass)

Opaline by Anna Carlgren (a study of how different types of glass influence each other when combined)

Du är min ögonsten/Apple of my eye by Anna Carlgren (with a human eye prosthesis)

Footed, scrambled periscope by Anna Carlgren (prisms from a periscope).

You are my rosebud II by Anna Carlgren (opaque white, porcelain-like glass)

Sources and references: 

The Corning Museum of Glass New York (Unbreakable Glass)

The New York Times (The nature of glass remains anything but clear)