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Gustave Falconnier's Blown Glass Bricks
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As of 2014, new #9 bricks are now being produced

Gustave Falconnier
Gustave Falconnier's signature
Gustave Falconnier
Scan: Nyon Archives


Falconnier briques at the house of Mihály Babits, famous Hungarian writer, poet, translator, and literary historian

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Falconnier briques in the Castel Béranger

Falconnier full and half-size bricks

Dora and Marinus Wassenbergh

Cobalt #9 brick from Cole's Book Arcade, via Victoria Museum
Falconnier brique seal
Brique seal
History: In the late 1880s, Architect/Engineer Gustave Falconnier [1845-1913] of Nyon, Switzerland, invented a novel type of glass building block or "glass brick" (German glasbaustein or glassteine, French brique de verre). Falconnier's bricks were blown in a mold (BIM) like bottles, but had the original feature of being sealed air-tight with a pastille of molten glass while hot (see right); after cooling, the hot air trapped inside contracts, forming a partial vacuum.

Unsealed glass blocks by Deutsche Luxfer Prismen-Gesellschaft
Glass blocks by Deutsche Luxfer Prismen-Gesellschaft
Marke Faust Unsealed glass blocks by Deubener Glaswerke
Marke Faust glass blocks by Deubener Glaswerke
Unsealed glass blocks by Siemens of Dresden
Glass blocks by Siemens of Dresden

The other early type of glass brick, made by Deutsche Luxfer Prismen-Gesellschaft, Deubener Glaswerke and Siemens (these last two very similar, see above) were unsealed and shaped (and sized) like traditional masonry bricks, but lacked a bottom surface. They had problems with condensation and dust collection on their interior surfaces, which could never be cleaned.

Falconnier's air-tight design, a prize-winner at the 1893 Chicago World's Fair and 1900 Paris Exposition, corrected these defects:

"By making such bricks or blocks hollow, especially when they are made air-tight, they possess several advantages over other materials, being cheap, light, durable, and ornamental. Further, by reason of their inclosing and confining air in a state of rest they serve as non-conductors of heat."US Patent No. 402,073

Falconnier's briques were manufactured by Albert Gerrer of Mulhouse (Haut-Rhin), S. Reich & Co. of Vienna and others. Their sides were recessed to take mortar and they were laid up like ordinary masonry bricks, with or without embedded metal reinforcing.

Haywards Ltd. bought the patent and marketed them in England for vault and window walls. Despite initial interest from important period architects such as Hector Guimard, Auguste Perret and Le Corbusier, and some prominent installations (La Mission d'Algérie, house of Mumm, etc), Falconnier's design was apparently not a great commercial success. The bricks are rare today, and existing installations even rarer. They suffered from the same defect as early vault lights: damaged glass could not easily be replaced. Falconnier briques are sometimes mistaken for fishing net floats.

Partial bricks: For finishing square openings, each pattern was also made in ¾, ½ and ¼ sizes. A ¾ brick finished the long side, a ½ brick finished the short side, and a ¼ brick finished a corner. Partial Falconnier bricks

Markings: Falconnier bricks are embossed a number of different ways; here are a few: (// separates panels, / separates lines on same panel)

  • Usually "FALCONNIER // DEP FRANCE / BELGIQUE +n" where n is the style#.
  • The seal often reads "FALCONNIER / D.R.P / 41773" where DRP is Deutsches Reichspatent and 41773 is his German patent number.
  • Just "FALCONNIER", nothing else (on my cobalt and amber #7s)
  • "FALCONNIER // 5" (on a light aqua #6 brick). Seal: "FALCONNIER / DR 10708". I don't know what the 5 refers to, but this is the flat-faced varation of the #6, so maybe the #5 is just not shown in the catalog.
  • "FALCONNIER // IMPORTE D'ALLEMAGNE // ADLERHÜTTE / PENZIG" (on my green #7½)
  • "FALCONNIER // No 9. ¼ // DLERHÜTTEN / PENZIG" on a clear #9¼-brick. Note, the 'A' from ADLERHÜTTEN is missing due to lack of room and the N is cramped; who planned that?
  • Just "GLASSHÜTTE GERRESHEIM" on a light aqua #9; the seal is unmarked.

Colors: Most bricks were light aqua, the usual color of glass made from sand with iron contamination (which is most sands, as any child who's played in a sandbox with a magnet can attest), but other colors were available at extra cost: clear for improved light transmission, and decorative colors amber, green, blue and (opal) milkglass (all colored in the mass). A red brick was made by casing a clear brick in a thin layer of expensive, gold-based ruby glass. The patent mentions coloring "either in the mass or by coating or covering them inside or outside in full or in part with layers of metal or paint", Additional ornamentation by sand-blasting, cutting and engraving, or acid etching is also mentioned, but I have yet to see these variations.

Value: Despite rarity, prices are low since there are very few collectors of early glass bricks (basically, me), so there is little demand. The most common brick, a #8 in light aqua, is difficult to sell at any price. I have seen hundreds for sale (often in large lots), and would price them at about US$5 in quantity, more singly. Rarer patterns, colors, and partial bricks are all worth more. The high end is about US$150.

Finis: Modern-style two-part fused glass blocks were perfected in the 1930s, more than forty years after Falconnier's bricks were introduced. Around the same time, Belgian company Etablissements Gaston Blanpain-Massonet of Bruxelles was still producing bricks in the #8 pattern (always the most popular) as seen in this catalog page, as well as the glass bricks of style Glasfabriek Leerdam.


Four basic shapes were produced: square (No. 6, in two variations), a lozenge or watch-with-band shape (No. 8), squashed hexagon (No. 9), and four variations of a regular hexagon (Nos. 7, 7½, 10 and 11). All tessellate, forming a repeating pattern that completely fills a space. No. 8 was the most popular shape and so is the most common now, followed by No. 9 (also fairly common), then regular hexagon and square, which are rare; I estimate the ratio at about 100:50:5:1.
Falconnier block glass brick No. 6 (front view) Falconnier block glass brick No. 6 (side view) Falconnier block glass brick No. 7 Falconnier block glass brick No. 8 (front view) Falconnier block glass brick No. 8 (side view) Falconnier block glass brick No. 9 (front view) Falconnier block glass brick No. 9 (side view)
No. 6 No. 7 No. 8 No. 9