[SoftTalker]

Ordinary incandescent bulbs must have similar sealing requirements, but they probably mostly rely on using a thin conductor that doesn't contract much when it cools. Also IIRC modern incandescent bulbs do not use a high vacuum but contain a low pressure inert gas so leakage would be slower if it occurs at all.

[adrian_b]

As you say, incandescent bulbs are less demanding because they do not use high vacuum, but they have the additional requirement that the pins that support the tungsten filament must resist to very high temperatures, because some heat is conducted through the filament into its support.

This is why the pins that support the filament are typically made of molybdenum. Molybdenum has a relatively low thermal expansion coefficient in comparison with most metals, so there are certain glass compositions that can match its TCE. The glass through which the pins pass is not of the same type as the bulb, which is made of cheaper glass, but it is of the type matched in TCE with molybdenum.

[ssl-3]

AFAIK, in in the US: Modern high-efficiency incandescent bulbs are exactly like the halogen bulbs of yore, but with the small quartz envelope wrapped in a familiar light-bulb-shaped shell, and with a base that matches. It's like a light bulb within a light bulb.

See this random example of a GE bulb (which I selected just because it includes the first picture I could find of a modern bulb made with clear glass): https://www.toolboxsupply.com/products/ge-lighting-62616-ene...

Except for all the ones that aren't modern or efficient. Common 40-Watt appliance bulbs, for instance: Those are still built using the old methods. They never changed. This strongly suggests that we never forgot how to seal metal wires into a glass bottle full of nothing.

But this article isn't about industrial processes. It's about rediscovering things at home, and that stands on its own merits. :)

[tliltocatl]

Incandescent bulbs used dumet/platinite, which is an nickel-iron alloy like kovar except it's turned for a different CTE. This stuff isn't that expensive when mass produced - it's just those who can afford usually borosilicate can afford paying a premium for kovar.

[sam1714]

Incandescent bulbs are 0.8 atm (equivalent to 15,000 ft altitude) when off, and when they're on, they're actually slightly pressurized.