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Fused Quartz Tube: Blown from Brazil Pebble in the Oxy-Gas Flame (Shenstone, 1916)
W. A. Shenstone · Public domain
Charlie

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Charlie

4. November 2026DE
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Fused Quartz Tube: Blown from Brazil Pebble in the Oxy-Gas Flame (Shenstone, 1916)

Fused silica stands sudden heating and cooling that would crack glass, but natural quartz splinters violently in a flame. W. A. Shenstone, in The Methods of Glass-Blowing and of Working Silica in the Oxy-Gas Flame (1916), first turns Brazil pebble into a "non-splintering" silica by quenching it from a yellow-red heat, then melts it in an oxy-gas flame into fine rods, wraps the rods round a platinum core into a first tube, and enlarges it with rings of rod blown out. Not given: quantities and times. He advises most workers to start from bought tubes and to learn each stage by practice. Source: W. A. Shenstone (1916), pp. 88-94. Picture: his p. 93.
Advanced
Several days of practice

Instructions

1

Read Shenstone

"The silica tubes thus made can be cut and broken like glass, they can be joined together before the flame, and they can also be drawn into smaller tubes when softened by heat."
2

Crack the Brazil pebble

Clean the chips of Brazil pebble (rock crystal) thoroughly, heat them in boiling water and drop them into cold water. Repeat until they have cracked enough to break easily with a clean steel pestle or hammer. Hand-pick the fragments and reject any that are not perfectly free from foreign matter.

Materials for this step:

Rock CrystalRock Crystal1 as required
WaterWater1 as required

Tools needed:

SaucepanSaucepan
Hot PlateHot Plate
BucketBucket
Ball Peen HammerBall Peen Hammer
3

Make it non-splintering

Heat the pure, transparent pieces to a yellow-red heat in a covered platinum dish in a muffle furnace and plunge them quickly into a deep clean vessel of distilled water. Repeat until they are semi-opaque, friable masses like white enamel. Wash them with distilled water, drain and dry. Now they can go straight into the hottest part of the flame without splintering.

Materials for this step:

Distilled WaterDistilled Water1 as required

Tools needed:

Platinum DishPlatinum Dish
Muffle FurnaceMuffle Furnace
Crucible TongsCrucible Tongs
Glass BeakerGlass Beaker
4

Set up the flame

Use an efficient oxy-gas burner fed with coal gas and oxygen from a bottle fitted with a gauge and regulator; watch the oxygen used. Protect your eyes with very dark glasses, so dark that work is a little difficult at first, and keep a second pair for long spells, as the glasses get hot. The hottest spot is near the tip of the inner cone: bring the work exactly there.

Materials for this step:

Coal GasCoal Gas1 as required
OxygenOxygen1 as required

Tools needed:

Oxy-Coal-Gas BurnerOxy-Coal-Gas Burner
Pressure Gas CylinderPressure Gas Cylinder
Pressure Reducing RegulatorPressure Reducing Regulator
Pressure GaugePressure Gauge
Shaded Forge GogglesShaded Forge Goggles
5

Draw fine rods

Hold a fragment in platinum-tipped forceps and melt one corner. Press a second fragment against the melted part until they stick, and heat from below upwards (to avoid bubbles) until it is clear. Add a third, a fourth and so on until you have an irregular rod. Reheat it in sections and draw it out into rods or coarse threads 1 to 2 mm across.

Tools needed:

Platinum-Tipped ForcepsPlatinum-Tipped Forceps
Oxy-Coal-Gas BurnerOxy-Coal-Gas Burner
Shaded Forge GogglesShaded Forge Goggles
6

Make the first tube

Bind a few rods round a platinum rod about 1 mm across with platinum wires at both ends. Withdraw the core slightly from one end and heat gradually from there until a rough tube 4 to 5 cm long has formed. Close one end, blow it into a small bulb, fix a silica rod to the far end of the bulb, reheat and draw it out into a fine tube. Blow a fresh bulb on one end and draw it out again, until the tube is 6 to 8 cm long.

Tools needed:

Platinum WirePlatinum Wire
Platinum-Tipped ForcepsPlatinum-Tipped Forceps
Oxy-Coal-Gas BurnerOxy-Coal-Gas Burner
Shaded Forge GogglesShaded Forge Goggles
7

Blow without soiling it

Blow through a rubber tube on the open end of the silica tube, with a glass tube loosely packed with granulated potash between your mouth and the work so the inside stays clean. Do not take a hot bulb out of the flame to blow it; move it just off the hot spot. Mend holes with plastic silica from the softened end of a fine rod and blow the lump out. Keep the silica clean: a white crust that forms is removed by reheating, but dust or handling can spoil the surface for good.

Tools needed:

Rubber TubingRubber Tubing
Glass TubeGlass Tube
Potassium Carbonate (Potash)Potassium Carbonate (Potash)
Oxy-Coal-Gas BurnerOxy-Coal-Gas Burner
8

Enlarge and lengthen

To widen a bulb into a tube, lay a ring of fine rod round its end, heat the ring and the end until soft and blow; repeat until the bulb becomes a short tube. For a long tube make several pieces 200 to 250 mm long at the diameter you need and join them end to end. Thicken a tube by adding rings and blowing them out. For a large tube, set a plate of silica behind the work to throw the flame back onto its far side.

Tools needed:

Oxy-Coal-Gas BurnerOxy-Coal-Gas Burner
Platinum-Tipped ForcepsPlatinum-Tipped Forceps
Shaded Forge GogglesShaded Forge Goggles
9

History and honest limits

Thorpe's Dictionary (vol. IV, 1913) records Gaudin spinning fused silica threads in 1839, Boys making quartz fibres in 1887, and Shenstone showing in 1901 how to make tubes and bulbs before the oxy-coal-gas blowpipe. Shenstone gives no quantities or times and says most workers save time and money by starting from bought silica tubes. A finished tube holds a little moisture and nitric peroxide; he removes them by heating it and drawing filtered air through, not by washing.

Materials

5
  • 2
    Rock Crystal
    1 as required
    Placeholder
  • 2
    Water
    1 as required
    Placeholder
  • 3
    Distilled Water
    1 as required
    Placeholder
  • 4
    Coal Gas
    1 as required
    Placeholder
  • 4
    Oxygen
    1 as required
    Placeholder

Tools Required

18

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Fused Quartz Tube

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