Liquid-in-Glass Thermometer: Bulb, Fill, Seal and Scale

A household or laboratory glass thermometer is a glass tube with a fine bore, a bulb at one end, and a measured amount of liquid sealed inside under vacuum. The liquid expands and contracts with temperature, and its level is read against a scale. Today the liquid is mostly a spirit-filled hydrocarbon rather than mercury. The bulb is formed on the tube, the tube is filled in a vacuum chamber, heated out and sealed, the 0 °C and 100 °C points are marked from ice and boiling water baths, and the scale is engraved through wax and fixed with hydrofluoric acid, a deadly poison.