A blowpipe is a steel tube 1.2-1.5 m long, 15-20 mm in outer diameter, with a 5-6 mm bore, a slightly flared gathering end and a mouthpiece at the other. A bare pipe of that size weighs roughly 1.4-3.4 kg, and the glass on the end adds to that, so the pipe length and wall are a compromise between reach and what a wrist can rotate for minutes. Any seamless mild steel tube works, and a rolled and forge-welded strip works when seamless tube cannot be found.
Part of Glass Blowing and Forming
The hollow steel tube on which glass is gathered, inflated and rotated.
The Pipe Is A Lever, A Handle And A Bellows Pipe At Once
The blowpipe carries the gather, lets the blower inflate it and is rotated constantly to keep the glass centred, so its length and weight set how large a piece one person can handle. The carrier article gives the dimensions above: 1.2-1.5 m long, 15-20 mm outer diameter and a 5-6 mm bore. The corpus’s Glassblowing article gives a slightly different range, 120-150 cm long with a 1-2 cm bore, and says a bore of at least 6 mm works and 10-12 mm is ideal. The two bore figures do not agree. A bore at the small end resists a first breath more; a bore at the large end leaves less steel around it.
What You Need
- Tube: seamless mild steel, 15-20 mm outer diameter, 1.2-1.5 m long.
- Gathering end: slightly flared. The carrier suggests thickening it by forge-welding extra metal for heat resistance.
- Mouthpiece: the cool end; a wooden or wrapped section stops the lips touching bare steel.
- A forge, to flare or thicken the tip.
If seamless tube cannot be found, wrap a strip of iron sheet around a mandrel and forge-weld the seam, as the glassblowing article describes; the bore need not be perfectly smooth.
Method: Making And Maintaining A Pipe
Step 1: Cut the tube to length. A longer pipe keeps the hands further from the gather and the glory hole; a shorter one is easier to rotate.
Step 2: Flare the gathering end. Heat it in the forge and open it slightly so the glass has a lip to grip.
Step 3: Preheat before every gather. The glassblowing article says to heat the tip to a dull red; cold iron cracks the glass.
Step 4: Clean the tip after every piece. Scale and old glass on the end spoil the next gather.
Worked Example
Steel density is about 7,850 kg/m³ (recalled, not from the corpus). Cross-section of a 20 mm outer, 5.5 mm bore pipe: π/4 × (20² − 5.5²) = 0.7854 × (400 − 30.25) = 0.7854 × 369.75 ≈ 290 mm². For 1.5 m that is 290 mm² × 1,500 mm = 435,600 mm³ = 435.6 cm³, times 7.85 g/cm³ gives about 3.4 kg.
A 15 mm pipe with the same bore: π/4 × (15² − 5.5²) = 0.7854 × 194.75 ≈ 153 mm²; for 1.2 m that is 153 × 1,200 = 183,600 mm³ = 183.6 cm³, times 7.85 gives about 1.4 kg. The pipe alone is therefore roughly 1.4-3.4 kg before any glass is gathered.
Common Mistakes
- A pipe too heavy for the blower. Rotation must be steady; a pipe that tires the wrist makes every piece lopsided.
- A blocked bore. Glass or scale in the bore stops the bubble. Clear it with a rod.
- A bare-steel mouthpiece. The cool end can still be hot after a long session; wrap it.
Safety
Never inhale through the pipe
Only blow out. Drawing breath through a pipe whose far end sits in a furnace pulls hot air and furnace fumes into the lungs. Use the tongue or thumb to seal the end between breaths, and keep the mouthpiece clean.
Hot glass does not look hot
A pipe or glass below about 600 °C shows no glow yet burns skin. Do not grab a pipe end that has been in the glory hole.
What’s Next
- Learn next: Gathering — loading the pipe
- Combine with: Pontil and Punty — the solid rod that takes the piece over