Diderot Encyclopedia: Making Crown Glass

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Diderot Encyclopedia: Making Crown Glass
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Diderot: 5 of 6

This is #5 of 6 engravings re-printed by the Corning Glass Center from originals in the Corning Museum of Glass, and released as "The Art of Glassmaking 1751-1772 / A Portfolio of Prints from the Diderot Encyclopedia". I added the original legends in French (from the ARTFL Encyclopédie Project) and my own loose English translations and commentary. The small image below links to a 4.1MB, 300DPI scan.

Making crown glass in eighteenth century France

Verrerie en bois, Grande Verrerie en Plats.
Intérieur d'une Halle et différentes Opérations de la Verrerie à Vitres.

Cette Planche représente l'intérieur d'une halle de grande Verrerie à plats pour les vitres, dite à pivette.
a a a		construction en charpente de la halle.
b b		four occupant le centre de la halle.
c c		calcaise à cuire les pots.
d		calcaise à cuire les frittes ou compositions du verre.
e		tonnelle ou passage pour arriver à la glaie.
f		cheminée pour jetter les pivettes ou bois secs du haut en bas de la halle.
g g		poches & autres ustensiles nécessaires pour le service de la Verrerie.
h h h		pivette ou bois coupé en petits morceaux d'environ dix-huit pouces, séchant sur le haut du four.
i		pivette ou bois sec prêt à être mis au four.
l		béquet pour retourner les bosses, & mettre le pontis pour former les plats.
m		chaudiere de fer, dans laquelle on met le sel qui surnage sur la surface des pots de verre dans le four.
n		tiseur portant de la pivette ou bois pour chauffer le four.
o		cueilleur occupé à tremper le bout de la felle ou canne dans le four.
p		gentilhomme qui alonge le cueillage à l'auge.
q		gentilhomme roulant la seconde chaude sur le marbre.
r		gentilhomme soufflant la bosse sur le crenio ou auge de mâçonnerie.
s		gentilhomme portant le plat à la pelote.
t t		four à recuire les plats.
u		crenio ou auge en mâ-çonnerie.
v		petit talut ou chemin du tisard.
x		marbre sur lequel on roule les chaudes ou bosses.
y		auge de bois pleine d'eau servant à alonger les cueillages.

Wood-burning glasshouse, Large and flat glass. Interior of a hall and various operations of the glass work.

This plate shows the interior of a large-glassware hall with glass windows.
a a a		construction and framing of the hall.
b b		furnace at the center of the hall.
c c		*calcaise* (small furnace) for firing pots.
d		calcaise to fire frit or glass mixtures.
e		passage to the *glaie* (furnace loading area).
f		chute for bringing down pivettes from above the hall.
g g		pans & and other glassmaking tools (casse, perche, pince, etc).
h h h		*pivettes* (wood cut into about 18" lengths and dried above the furnace).
i		pivettes or seasoned wood ready for the furnace.
l		*béquet* for turning over the *bosse* (parison, first bubble) to attach the ponty (transfer rod).
m		iron boiler, for salt skimmed off the top of the pots.
n		stoker carrying pivettes or wood to heat the furnace.
o		gatherer dipping the end of the blowpipe in the pot.
p		worker lengthening the gather at the trough.
q		worker rolling the gather (after second heating) on the marver (marble or iron plate).
r		worker blowing the bosse at the *crenio* (masonry trough).
s		worker carrying the plate to the *pelote* (round heap of fine embers mixed with ash, flattened on top, to place the plate on).
t t		lehr (annealing oven) for the plates.
u		*crenio* (masonry trough).
v		petite talut (descending ramp to tisard).
x		marver on which the glass is rolled.
y		wooden trough filled with water; used to lengthen the gather.

The batch (raw materials) are melted in the furnace in clay pots (not visible), whose tops are accessed through the ouvraux (glory holes, o). The furnace is fired with ordinary seasoned wood or pivettes (oven-dried sticks about 18" long), fed into the furnace via the glaie. The pivettes are dried in the rafters of the furnace-heated hall (hhh), then thrown down a chute, where they can be accessed at ground level.

Each piece begins with the gatherer (o) collecting a gob of molten glass on the end of a blowpipe, which is then shaped, re-heated, and shaped again (p, q, r). Once the hollow form is opened up at its end, the blowpipe is spun and the centrifugal force causes the glass to open up into a flat, round plate (s). When cooled enough to solidfy, it is set down on a pelote and detached from the punty. Finally, plates are placed in the annealing oven (lehr, tt) to remove stresses.