Tag: stained-glass

Mémoire d’atelier sur trois projets @ été78, Bruxelles – vernissage 18/02/2017


3 exhibitions in a row at ETE78, rue de l’été n°78, 1050 Brussels!

Vernissage Feb. 18th from 4PM to 8PM







1PM – sun starts illuminating the background


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I just received these two pictures from the glass studio Debongnie – my partner in stained-glass. A prototype-window that will be presented next week for the final of a competition.



Rosace, quasicristal dodécagonal


Variations of the visual appearance of a stained glass window during the course of the sun in the sky.

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Le ciel, le soleil et un vitrail orienté Est


[Document in French] A timeline of the visual appreance of a stained-glass, in parallel the colors of the Sunlight and the colors of the Sky, during a sunny summer day.

(PC : click-droit > “ouvrir l’image dans un nouvel onglet” pour voir l’image en grand)

(right-click > “open image in a new tab” to zoom)

Sunlight / Stained-glass

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Simulation of the changing visual appearance of an East-oriented Stained-glass window depending on the daylight color and orientation:

7:30 AM: before the sun rises, the sky illuminates the window

7:45 AM: a yellow Sunlight reaches the window

8:00 AM: the Sunlight is already whiter

12:00 AM: the Sunlight is white

12:30 AM: the Sunlight disappears, only the sky illuminates the window

4:00 PM: idem

6:00 & 8:00 PM: the sky’s color changes slightly

All this has been simulated using physical data about the light of the Sun and the Sky in the south of France, and physical data acquired by scanning colored glass with a spectrophotometer.


14 steps of an algorithm

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This gives you an idea of how I work. Every operation is the result of hundreds lines of code, but the logic is pretty simple. We have a quasiperiodic cristal made of triangles and we detect regular shapes (squares, diamonds, octogons, 6-gons, etc.). This creates a pattern that’s later gonna be made of little glass pieces.

Glass-light interactions on the prototype


With the studio Debongnie (, we are working on a Stained-Glass prototype to be installed in a 13th Century Cistercian Abbey in the south of France. My project passed the pre-selection and we are in the final of the competition against 2 other duos artist/glass-studio.

Cistercians didn’t put colors, pictures or crosses on their windows. Their windows were supposedly « albae fiant, et sine crucibus et pricturis » (white – or colorless(?) -, and without cross and representations). Very few original 12 & 13th Century Cistercian windows survived and we know little about how they interpreted this rule.

My proposal is to produce “white light” in the Abbey, by a combination of different optical types and colors: transparent light greenish blue, light blue and light reddish blue mostly, and opalescent whites that diffuse light and are less transparent.


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During the course of a sunny day, the light will vary. The visual appearance of the window will be changing a lot because of this variation.

Behind the window is a yellowish-white stone-wall. Before noon the window and the wall behind it are in the shadow. Around noon, the sun illuminates the window directly and the opal glass are becoming very bright. During the afternoon the wall behind becomes illuminated, allowing the transparent colors to appear. Finally around 4-5PM the shadow moves on the window and the opal glass stops being so bright.


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Interestingly, opal glass will appear white but will project amber light on the walls or the floor of the building. The average color of the light passing through the window has been computed to be white. The glass selected last month in the factory Lamberts in Waldsassen were chosen to produce this effect, and the situation has been simulated with the light spectrum as measured last summer in the south of France.



Finally, there’s the possibility of seeing the sky from an angle in the Abbey. When people will look at the window with the sky behind, it will reveal new colors again. What looked almost colorless will appear as different shades of blue and yellowish whites.


Picture of the first third of the window-prototype


Finally, the glass version !

This is a stained glass element made with a traditional technique. The black lines are a combination of hand painted “grisaille” and lead.

I’ll soon describe the entire project in a longer post, stay tuned ;)


glass prototype making

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Next week we’ll finally be able to judge the result.

Preview of prototype placed in-situ


probably not accurate, but it gives a first idea.

The map!


the map of the stained-glass

This is really the result of intense work during 4 1/2 months. More news soon.

Simulation of “Opal” glass


Opal glass is a strange material. It is a colorless glass that scatters blue light in the same way the earth’s atmosphere does it with sunlight: the sky is blue because blue sunlight doesn’t travels straight in large thicknesses of air, but in every directions. The sun appears yellowish because of the same reason: the blue part of the sun’s light spectrum has partly vanished from its rays under the form of blue sky.

In the opal glass, a very thin layer of diffusive “milky” glass containing very tiny particles is plated (“plaqué”) on the glass. Opaque white “flashed-glass” and opal “flashed-glass” are exactly the same material, but on the opaque version the layer of milky glass is very thick, up to 1 mm, while it can be maybe a 100 times thinner on very light opal glass.

It is very difficult to simulate the color of this glass on the computer: on the light table you see nothing but what seems to be a “cloudy” or “hazed” white glass. You need some distance to see the color appear, you need the light rays to pass in straight lines through  the glass otherwise the color won’t appear.

I did some research and I arrived to some pretty good results. The numbers under the pictures indirectly refer to the thickness of the milky layer. The left color is the one that appears by light transmission, the right one by light scattering.

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When the layer gets really thick, transmission becomes zero and the glass is opaque and white.


It’s really “white” but the light passign through it becomes yellow-brown.


Opal glass collection


I spent this week in the glass studio Peters Glasmalerei in Paderborn (Germany) and came back with a few opal-plated mouth-blown antique glass samples.


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