Molten Glassblowing Simulator (2D)

Furnace Heat

Reheat rate 40

Blowing

Blow pressure / rate 30

Gob is soft and glowing — starting to inflate.

Live Readout

Bubble radius

2.0 cm

Wall thickness

6.0 mm

Glass state

Molten

Temperature

1100 °C

How it works

Molten glass behaves like an extremely viscous fluid rather than a solid: its viscosity falls exponentially as temperature rises, which is why a glassblower keeps returning the piece to the furnace ("reheat rate" here) to keep it workable. Cold glass is effectively frozen solid and will not flow at all.

Blowing down the pipe raises the internal pressure of the bubble. That pressure fights the glass's own surface tension, which resists expansion the most sharply when the bubble is small (Laplace pressure ≈ 4σ/R — the smaller the radius, the harder it pushes back). Once the bubble has some size, the same puff of air expands it more easily.

Because the total volume of glass in the wall stays constant as it stretches, wall thickness shrinks roughly as the inverse square of the radius — doubling the bubble's radius quarters its wall thickness. Meanwhile the glass is always losing heat to the room; as it cools, viscosity climbs, the bubble stiffens, and further blowing barely changes its shape until it's reheated.

Click/tap the bubble for a puff · adjust sliders to reheat or blow