This is by no means difficult, but is easier with lead glass than with soda glass.
This remark is more important in the case of soda than of lead glass.
lead glass should be heated for this purpose in the oxidising flame (pp. 17 to 22).
I have found that the larger size, with a powerful bellows, heats large pieces of lead glass very satisfactorily.
The, work is exposed to this flame until, in the case of lead glass, traces of reduction begin to appear.
The same thing will happen in bending a lead glass tube if it is made too hot in a luminous flame.
Many amateurs find that soda glass is in some respects easier to work with than lead glass.
To collect the glass for blowing a bulb of lead glass, employ the flame described on pp. 17-22 for heating lead glass.
Nickel produces an amethyst color in potash-lime glass, a reddish brown in soda-lime glass, and a purple in lead glass.
As is well known, there are two general varieties of glass: lead glass and soda glass.