I haven't seen many blue JD pintypea before, but seeing them now, I have to say: I really like them!

They are nice to see in the air, yes. That blue glaze was THE standard glaze for all Jeffrey-Dewitt insulators for 23kV to 66kV as well as their suspension disk.

One fun fact about J-D insulators is that they are cast in molds, so you end up with a solid mass of porcelain that is impossible to 'puncture' by lightning! Regular multiparts and large uniparts are thinner, as they are pressed and turned before glazing. The problem, though, is that the casting process is so much more expensive than the processes to make other types of wet-process porcelain. J-D started up around 1920 and was forced to switch to conventional styles and processes by 1940, and the facility (at Parkersburg, WV) burned down in 1952.

That's interesting. That must explain why their disk insulators have a different profile. It's too bad the company burned down in 1952 because they made some good insulators.

That's a great find and shot!

The J-D disks have a fatal flaw: the spiders mounted on the ends of the porcelain disk put a tension load on the porcelain, whereas the modern steel-capped suspensions have the inside of the cap and the end of the inner pin formed such that it is a compressive load.

Porcelain is weak when loaded in tension, and when several major lines equipped with J-D disks had insulator failures (dropped conductors), the industry switched back to the older Hewlett suspensions until the last remaining issues with the steel-capped suspension disk (mostly cement 'growth' issues) were resolved.

Those J-D disks that did not fall apart back then (or taken out of service by utilities wanting to be rid of them) have mostly remained in service to this day, only coming down when the line gets a total rebuild. Some of the structures at Hoover Dam on the Arizona side still have their original JD disks! (you can see them supporting the jumpers on the structures along the edge).