To gather glass, heat the tip of the blowpipe in the glory hole until it glows, dip it into the molten glass in the crucible and rotate it slowly so the glass wraps around the tip like honey on a spoon, then withdraw while still turning. The gather must be centred and symmetrical, and a solid gather 7-8 cm across weighs roughly 450-670 g. Never stop rotating, because hot glass sags under gravity and the gather will deform and drip.
Part of Glass Blowing and Forming
Collecting molten glass on the end of the blowpipe from the crucible.
A Good Gather Is Centred Before It Is Large
Every later operation starts from the gather, so a gather that is off-centre or poorly bonded to the pipe cannot be corrected by good blowing. The carrier lists five steps; this article adds what to look for at each.
What You Need
- A crucible of glass at working temperature, with the glass surface skimmed of scum; the furnace opening should be large enough for the pipe and no larger.
- A preheated blowpipe; see The Blowpipe.
- A marver for the next step.
Method: Gathering
Step 1: Preheat the pipe tip in the glory hole. The carrier says cold iron cracks glass.
Step 2: Dip and rotate. Insert the tip into the crucible and rotate the pipe slowly. The molten glass wraps around the tip.
Step 3: Withdraw, still turning. The turning prevents dripping.
Step 4: Check the gather. It should be symmetrical and centred on the pipe. If the gather hangs off-centre, turn the pipe and let gravity settle it, then marver.
Step 5: Gather again if needed. The glassmaking article suggests a golf-ball-sized first gather while learning, and the glassblowing article describes a first gather for a small vessel as roughly the size of an orange, which this article takes as 7-8 cm across.
Worked Example
Gather weight sets how much arm and wrist you need. A glass sphere of 7 cm diameter has volume 4/3 × π × 3.5³ = 4.19 × 42.9 ≈ 180 cm³; at 8 cm diameter, 4/3 × π × 4³ = 4.19 × 64 ≈ 268 cm³. Soda-lime glass has a density of about 2.5 g/cm³ (recalled, not from the corpus), so the gather weighs about 180 × 2.5 = 450 g to 268 × 2.5 = 670 g. This sits on a bare pipe of roughly 1.4-3.4 kg; see the worked example in the blowpipe article. The pipe, not the glass, dominates the load, and the glass concentrates it at the far end.
Common Mistakes
- Dipping a cold pipe. The glass cracks off.
- Stopping rotation. The corpus warns that the gather will deform; keep turning.
- Gathering from a crucible that is too hot. The carrier says above the working range glass runs like water, and it will not hold on the pipe.
Safety
Hot glass does not look hot
Drips and strings of glass that fall from the pipe go below about 600 °C within moments and look like cold fragments on the floor while still burning skin. Do not pick them up barehanded.
Heat and glare from the opening
Working at the furnace opening exposes face and arms to radiant heat; wear dark eye protection and a face shield.
What’s Next
- Learn next: Bubble Formation — turning the gather into a parison
- Combine with: Glory Hole — preheating and reheating