Borosilicate Glass Tube and Rod: the Vello Process

Laboratory borosilicate glass is about 80% silica, 13% boric oxide, 4% sodium or potassium oxide and 2–3% alumina, melted from boric oxide, silica sand, soda ash and alumina. It melts hotter than ordinary glass. Tube and rod are drawn continuously from the melt. In the Vello process, which L. Sanches-Vello developed in France in 1929, the glass flows down through a ring-shaped opening between the feeder's outlet nozzle and a hollow needle, and air blown through the needle keeps the tube open. The tube sags from vertical to horizontal, runs along a roller track to the drawing machine, and is cut into pieces about 1.5 m long. The nozzle runs cooler than in the older Danner process, which suits glass with volatile borates. Without the needle, the same feeder makes rod.

高级

Factory process

说明

Melt the batch

Melt silica sand, boric oxide, soda ash and alumina in proportions giving about 80% silica, 13% boric oxide, 4% alkali oxide and 2–3% alumina.

此步骤所需材料：

石英砂1 as required

氧化硼1 as required

碳酸钠（纯碱）1 as required

氧化铝粉（三氧化二铝）1 as required

所需工具：

玻璃熔窑

Draw through the Vello feeder

Let the glass run through the annular opening between the feeder's outlet nozzle and the height-adjustable hollow needle. Blow compressed air through the needle to inflate the tube. Set the needle slightly off-centre so the wall comes out even after the bend. For rod, run without the needle; the diameter is set by the nozzle and the drawing speed.

所需工具：

Vello 拉管供料机

Bend, draw and cut

Let the tube sag from vertical to horizontal, draw it along the roller track to the drawing machine, and cut it into pieces about 1.5 m long. Vello tube can be made from 1.5 to 70 mm in diameter.

所需工具：