Royal Institution of Great Britain · The Making of a Sheet of Glass · Page 13

When the cylinder has been drawn up to a height of 40 ft. it is cut off from the bottom. A hoop is put round the end of the cylinder and it is lowered on to a horizontal cutting frame. The remains of the cylinder are melted out by turning the pot over, while exposing the clean side of the pot ready for the next charge. The cylinder, about 36" in diameter, is now lowered on to the frame, where it is cut up into sections by means of an electrically heated wire, which takes the place of the glass thread of the old glass blower.
    Each cylinder is cut up into several sections and these are split longitudinally into three pieces called shawls, ready for flattening. The shawl is then taken to the flattening kiln. It is placed on to a carriage which inserts it into the kiln, where it is gradually heated up to a temperature ready for flattening. The flattener lifts the shawl off the carriage and opens it out on to a flat stone. It is then smoothed off by means of a wooden block at the end of an iron rod.
    From the flattening kiln the glass is passed down a chamber where it is annealed, bringing it to the delivery end cool enough to handle. It is now dipped in water to clean off the scum which is due to sulphur in the gas from the annealing chamber.
    FLAT DRAWN. Any sensible person will begin to wonder why the glass maker has spent all these years in making an article in a cylindrical form which is required in flat sheets. The main problem involved in drawing a flat sheet is firstly the maintenance of the width of the sheet, as without perfect temperature and mechanical control it tends to draw to a point, and secondly the maintenance of the generation point of the sheet in a straight line between the two extremities.