582 Mr. Tennant's Account of an easier Mode, &c. 
The principal point to be attended to, both in this and in the 
common mode, is the giving a strong heat, which should be 
continued for the greater part of an hour; and to enable the 
iron barrel to support this, it is quite essential to cover it with 
a proper lute, carefully applied. 
The lute which I have found most effectual for this purpose 
was composed of a small proportion of Stourbridge clay in its 
natural state, with a much larger proportion which had before 
been burnt and powdered, and both of which may be easily 
had at any glass house. 
