Blowing a Glass Bottle by Hand — Free-Blown Vessel Shaping

Bring the glass furnace to working temperature (~1100°C) with a crucible of molten soda-lime glass. Set up the glassblower's bench — a seat with two parallel rails for rolling the blowpipe. Have all tools within arm's reach.

If starting from raw batch: combine approximately 60% silica sand, 25% soda ash, and 15% crushed limestone. Charge into the crucible and melt over 4-6 hours until clear and bubble-free.

Pre-heat the blowpipe tip in the furnace mouth for 30 seconds. Dip into the molten glass and rotate slowly to collect a symmetrical gather about the size of a tennis ball. Withdraw smoothly.

Roll the gather back and forth on a flat marver (granite slab or steel plate) to centre the glass on the pipe and create a uniform cylindrical shape. Keep the pipe rotating constantly to prevent the glass from drooping.

Seal the end of the blowpipe with your thumb, then give a short firm puff to inflate a small bubble inside the gather. This first bubble (the 'parison') is the foundation of the bottle shape. Roll on the marver again to even out the walls.

Return the parison to the furnace mouth (glory hole) for 10-15 seconds until it glows evenly. Blow again to enlarge the bubble to the desired bottle size. Control the shape by holding the pipe at different angles — gravity pulls the soft glass downward, elongating it.

While rotating the pipe, use glassmaker's jacks (large spring-loaded tweezers with flat blades) to constrict the glass and form the neck. Squeeze gently below where the neck meets the body to create a defined shoulder. Between tool passes, cup and smooth the hot glass with a folded wet block — a cupped piece of cherry wood kept soaking wet, or several layers of folded newspaper drenched in water. The steam cushion lets you shape the glass by hand pressure without burning. Keep rotating to maintain symmetry.

Hold the pipe vertically with the bottle hanging down. Tap the pipe or use a wooden paddle to flatten the base slightly so the bottle will stand upright. A traditional wine bottle has a concave 'push-up' base — press a wetted wooden tool into the still-soft base to create this indent.

Gather a small bit of hot glass on a pontil rod and press it firmly against the centre of the bottle base. Allow it to fuse. The pontil will hold the bottle while the lip is formed.

Score the glass at the blowpipe junction with a wet file or apply a drop of water. Tap the pipe to crack off cleanly. The bottle is now held by the pontil rod with the neck opening upward.

Reheat the rough neck opening at the furnace mouth. Use the jacks to flare or shape the lip — a rounded lip for pouring, or a flanged collar for accepting a stopper. The lip must be smooth and even.

Apply a wet iron to the pontil junction and tap to separate. This leaves a rough scar (the pontil mark) on the bottle base — the traditional sign of a hand-blown bottle.

Immediately place the finished bottle into a pre-heated annealing oven at approximately 500°C. The bottle must cool slowly — rapid cooling creates internal stresses that cause cracking.

Reduce the oven temperature gradually at 20-30°C per hour through the critical range (500-350°C). Below 350°C the cooling rate can increase. A typical bottle anneals fully in 8-12 hours. Do not open the oven until the temperature matches room temperature.

Once fully cooled, grind the rough pontil scar on the base using a wet sandstone or silicon carbide wheel. The base should be flat enough for the bottle to stand without rocking. Inspect the entire bottle for cracks or thin spots.