Glassblowing Pipe Size Calculator
Find the right blowpipe diameter and length for your glass piece.
Match pipe size to gather weight and technique.
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:
| Gather Weight | Bore (mm) | OD (mm) | Length (cm) | Typical Piece |
|---|---|---|---|---|
| 50–200 g | 6–7 | 19–22 | 100–110 | Ornaments, small cups |
| 200–500 g | 8–9 | 22–25 | 110–120 | Tumblers, bowls |
| 500–1000 g | 9–10 | 25–28 | 120–135 | Vases, pitchers |
| 1000–2000 g | 10–11 | 28–30 | 130–145 | Large vases, platters |
| 2000+ g | 11–12 | 30–32 | 140–150 | Sculptural work |
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.