Glassblowing Pipe Size Calculator

How blowpipe sizing works:

The blowpipe (also called a blowtube or blowing iron) is the primary tool in glassblowing. Choosing the correct pipe diameter and length is critical — a pipe that is too thin for a large gather makes inflation difficult, while a pipe that is too thick for a small piece wastes heat and gives poor control.

Key pipe dimensions:

• Bore diameter: The inside hole through the pipe, typically 6–12 mm. Controls airflow and inflation rate.
• Outside diameter: The full thickness including the steel wall, typically 19–32 mm. Determines heat absorption and weight.
• Length: Standard range is 100–150 cm (40–60 in). Longer pipes put more distance between the artist and the furnace heat.

Pipe sizing by gather weight:

The physics of inflation: The initial air pressure needed to start a bubble in molten glass depends on the glass viscosity and the bore diameter. Larger bores require less lung pressure because force = pressure × area. A 10 mm bore has 2.8× the cross-sectional area of a 6 mm bore, making inflation significantly easier with heavy gathers.

Pressure required ≈ (4 × Surface tension) / Bore radius

For soda-lime glass at working temperature (~1050°C), surface tension is approximately 0.3 N/m. With a 10 mm bore (5 mm radius): P ≈ (4 × 0.3) / 0.005 = 240 Pa — easily achievable with gentle breath.

Worked example: You want to blow a medium tumbler with a ~400 g gather:

• Recommended bore: 8–9 mm
• Recommended OD: 22–25 mm
• Recommended length: 110–120 cm
• A 9 mm bore at 115 cm is a versatile choice for this range

Pipe material and weight: Standard blowpipes are stainless steel (usually 304 or 316 grade). Approximate pipe weight:

• 100 cm, 22 mm OD: ~1.4 kg (3 lb)
• 120 cm, 25 mm OD: ~2.0 kg (4.4 lb)
• 140 cm, 30 mm OD: ~3.2 kg (7 lb)

Beginner tip: Start with a mid-range pipe (8 mm bore, 22 mm OD, 110 cm long). This covers small to medium pieces and is light enough to handle comfortably while learning.