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Old 10-29-2020, 03:33 PM
 
Location: near bears but at least no snakes
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I have a lamp that is from the 1920s and I took it to be restored. (My cousin's cat had knocked it oven and chipped the glass.) He fixed the glass so that you would never know there have been any damage.

We put two lightbulbs into the lamp and have been using it for at least a year. Last week one of the bulbs exploded! I took the remaining bulb out and the wattage was 60. I have no idea what wattage the other bulb was because there was nothing left of it. There isn't even a marking on the metal part.

Can someone explain what caused the bulb to explode and what wattage I should be using? Or is something wrong with the wiring in the lamp?

Here's the lamp--at the top it divides into two sections where you have sockets for the bulbs and each has a pull chain.

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Old 10-31-2020, 06:41 AM
 
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A power surge can cause a incandescent bulb to explode but first thing I would look at is the socket to make sure a bulb screws into it and is nice and tight and the spring connection at the bottom is high enough to make a good solid connection. If a socket is not tight and the spring connector at the bottom is not in good contact, that causes the electrons to jump and that creates heat.

SO UNPLUG IT and check the tightness and that bottom spring connection and replace if necessary.

However, if that lamp still has the original sockets and wiring, I would suggest replacing the sockets and wiring. Normally an easy project, depending on setup; hardest part can be fishing the cord through the lamp.
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Old 10-31-2020, 08:10 AM
 
Location: Baker City, Oregon
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The bulb wattage had nothing to do with it.
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Old 10-31-2020, 09:03 AM
 
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Using two 60 watt lamps in that fixture is pushing it.

I'll start by saying that the design may have been intended for two 25 watt lamps or even smaller. When electricity in households first became common, expected levels of light were nowhere near as bright as we want today. The lighting that was replaced was dim in comparison at best. A candle gives off one lumen, and was the standard. Oil lamps (whale oil and kerosene) did a little better. Gas lamps could put out more, but heat buildup would have kept turning them to full brightness from being common. To someone only used to such lights, a 25 watt lamp was brilliant, and 50 watts was sheer indulgence.

That conical cover has no hole for excess heat to escape. Instead, it builds at the top of the cone. Depending upon the positions of the sockets, the bases of the lamps can be subject to excessive heat.

So why the exploding lamp? There are a few possibilities, but a variation of the following is common:

An incandescent lamp base has a small "fill" tube, where during manufacture the entire lamp is subjected to a vacuum and then the capsule (bulb) is filled with inert gas to about 3/4 of normal air pressure. That tube stem is then melted shut and the glass with protruding wires mechanically affixed to the metal part of the lamp you screw into a socket. When the lamp is powered on, the gas in the capsule tries to expand, but is held by the capsule, so the pressure rises in the lamp to around normal atmospheric pressure. The thin glass of the capsule is designed to handle such range of pressures.

When a bulb base is overheated, or overheated and then cooled repeatedly, the glass in the base in placed under stress and may eventually crack without a visible crack appearing on the capsule. Over time, the heated inert gas escapes and during the cooling of the lamp, regular air and humidity drawn in. That process repeats until at some point the air and water in the capsule get the pressure inside to normal atmospheric pressure when the lamp is cold. When the lamp is powered on, the gases try to expand and any moisture inside turns into a tiny amount of superheated steam, exploding the lamp from the pressure.

If the lamp was refurbished, the wiring should have been replaced. The heat from using too high a wattage may have damaged the sockets, but that is unlikely.

Your solutions are to use the historically correct wattage lamps, or use LEDs that have a lower actual wattage but give out similar amounts of light to your 60 watt lamps. If you go this route, be sure to buy LEDs designed for enclosed fixtures.
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Old 10-31-2020, 05:46 PM
 
Location: near bears but at least no snakes
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Thank you both for your answers. It scares me because I was sitting right next to it when POOF! Glass shards flew all over. All that was left was the socket and a wire.

I hope the guy who restored it made sure the wiring was okay. It makes sense to me that since this lamp dates from the days of early electricity, the bulbs should have been low wattage. Beyond that, I'm clueless when it comes to such things. However, I will check with someone who might be able to tell if the socket is damaged and I'll look for low wattage bulbs.
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Old 10-31-2020, 05:51 PM
 
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If the bulb exploded, that makes me think that the seal on the bulb broke and oxygen got in.

A power surge will cause the filament in the bulb to melt, but not explode (again, there's no oxygen in the bulb).
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Old 10-31-2020, 05:54 PM
Status: "I've got a fightin' side a mile wide but I pray for peace" (set 26 days ago)
 
Location: Florida
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Quote:
Originally Posted by TexasLawyer2000 View Post
If the bulb exploded, that makes me think that the seal on the bulb broke and oxygen got in.

A power surge will cause the filament in the bulb to melt, but not explode (again, there's no oxygen in the bulb).
This X2
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Old 11-01-2020, 06:27 AM
 
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https://www.scientificlights.com/hom...lbs-to-explode
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Old 11-01-2020, 10:15 AM
 
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Quote:
Originally Posted by f5fstop View Post
This article does mention something similar to what I was going to suggest as a possible cause.

We sometimes find the bulbs in a couple of our lamps get coated with residual cleaning product. Like when we clean/polish the lamp base or the table on which the lamp sits some residue makes its way to the bulb and over time it gets a film which I bet weakens the glass. Or at least contributes to overheating.
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Old 11-01-2020, 11:31 AM
 
Location: near bears but at least no snakes
26,646 posts, read 28,501,980 times
Reputation: 50468
Quote:
Originally Posted by TexasLawyer2000 View Post
If the bulb exploded, that makes me think that the seal on the bulb broke and oxygen got in.

A power surge will cause the filament in the bulb to melt, but not explode (again, there's no oxygen in the bulb).
The filament was intact. I was left with the socket and some ragged glass around it, the filament and a little flat square glass thing at the end of it. The 60 watt bulb in the other socket was not affected. Funny, but upon examining that damaged bulb, there was no wattage marked on the metal area so I have no idea now of what the wattage was.

I guess I'll go with low wattage LEDs next time.
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