THE GLASS INDUSTRY. 
advantages over the English furnace are: The furnaces are smaller and 
give a much higher temperature, with less fuel consumption, greater 
ease in regulation, cleaner conditions, and no clinkering of fuel when a 
pot leaks. The batch is melted at night, and within 24 hours a new 
batch is ready. 
A 10-pot furnace, taking pots about 80 inches diameter, holding 
$ ewt., will turn out 15 to 18 tons a week, consuming about 18 tons of 
D3 
fuel. The building cost varies from £1,600 to £2,000. 
The great disadvantage is that on reversing the direction of the 
burning gases the greatest heat is brought suddenly on to the cooler pots, 
and the sudden fluctuations in temperature considerably shorten the life 
of the pot by causing it to crack. A pot iS an expensive article, often 
costing about £10 by the time it is in position in the furnace. 
In the Hermansen recuperative type, by an arrangement of fireclay 
tubes the waste gases drawn off through the chimney first pass through 
a series of horizontal flues which surround the channels by which the 
air is drawn into the combustion chamber. Here the incoming air is 
preheated ready for combustion with the producer gas, and the regula- 
tion of the furnace heat becomes a simple matter of controlling the 
draught by means of the dampers provided in the main flue. No re- 
versing of the direction of the draught takes place, and a more even 
temperature is thus maintained throughout. The batch varies from 5 
to 12 ewts. per pot, according to the size of the furnace—4, 6, or 8 pots 
—and is melted nightly. About 20 tons of metal are produced with a 
fuel consumption of 16 tons. The initial cost varies from £800 to 
£1,200. 
— The Tank Furnace——The commoner and cheaper types of glass are 
‘melted in a tank furnace. This consists of a somewhat rectangular 
shaped compartment 18 inches to 24 inches deep, whose bed and walls 
are constructed of specially selected fireclay blocks, and varies in length 
from 30 to 100 feet. The mixed materials of the batch are introduced 
at one end at intervals as it melts down, and are worked towards the 
opposite end, where the molten metal is withdrawn through the openings 
provided for the glass-blowers. 
Across the chamber, half-way along, is placed a bridge, with its edge 
almost level with the surface-of the metal and serving to keep back all 
-unmolten material and skum, thus keeping the metal for working much 
cleaner. The melting and the working are continuous. The capacity 
varies, but some give as much as 300 tons a week. Tank furnaces are 
simple, and melt glass economically, but the metal produced is not of 
such quality as that from pots. With improved methods of firing, the 
tank may be used in the future for plate and window glass making, on 
account of the quantity it holds. This‘is the common type of furnace 
found in Australia. .The Hermansen furnace was first introduced into 
Scandinavia when the industry was so hard pressed by German pro- 
ductions. It is continuous in action, one running there for two years, 
melting 8 tons of soda glass per 24 hours. The temperature can be 
quickly raised to over 1,400°C. 
As optical glass, resistant glass, and various other types are made by 
melting the batch at high temperatures, most of the English furnaces 
were incapable of producing these, and in many directions we were 
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