nosehole

A nosehole is a small opening in a flattening furnace through which heat is directed onto the underside of a crown glass globe during the early stages of the flattening process. The opening sits low on the furnace face, positioned so that a glassmaker can hold the hot globe directly before it, keeping the glass workably soft as it begins to spread and level out from its spherical form.

Crown glass, which has a characteristic bullion or thickened center knot, must be gradually softened and encouraged to flatten under its own weight and carefully controlled heating. The nosehole provides a concentrated, directed heat source for this critical initial phase, before the globe moves to the main flattening surface or annealing oven. The opening is typically small enough to focus the furnace's radiant and convective heat precisely, preventing uneven softening or uncontrolled slumping.

The name reflects its physical location and function: it sits like a small nose protruding from the furnace face, at the point where glasswork begins. Historical furnace designs varied, but the nosehole concept appears consistently in crown glass production across European and American shops from at least the 18th century onward. Its positioning allows the glassmaker direct sight of the work and control over heating without moving the piece far from the heat source.

Timing and temperature control at the nosehole are critical. If the glass becomes too stiff, it will crack under the spreading forces; if too soft, it will collapse unevenly or stick to the work surface. Experienced makers judged readiness by color and viscosity, moving the globe away from the hole and onto the flattening table only when the edge began to surrender to gravity and gentle manipulation.