The making of insulators?

[carobran]

How were insulatore made?Were they blown into a mold like bottles?

 

[BillinMo]

Short answer is no -- insulators are pressed glass.

Rather than me writing lots of blathering to try to describe it, here's a diagram of a fairly simple insulator press: http://www.nia.org/timeline/patents/0113393.gif

Of course, in the decades after the 1870s things became more and more automated, but I think you'll get the idea.