Opening up a lightbulb

[PhotonWrangler]

How many CPFers does it take to open a lightbulb? Hopefully only one...

I'm disassembling a regular 100 watt clear lightbulb to turn it into a decorative thingy. I've managed to get into it by removing the bottom contact and insulator, but now I need to remove the metal Edison base from the glass envelope without breaking it.

The glass bulb is glued to the metal base with some sort of epoxy adhesive. Am I likely to be able to dissolve the epoxy with something, or am I better off heating the metal base with a heat gun or torch to get it to expand enough to crack the epoxy?

:thinking:

 

[Diesel_Bomber]

I wonder how hot that metal base gets during operation, especially base up? Even though you'd be heating the metal and not the glass, I don't know that thermal expansion of metal that thin would be enough to crack the epoxy.

Good luck. I look forward to learning whatever you figure out.

:buddies:

Edit: If you don't need the electrical contacts intact, a strong acid would take the metal right off, but I don't know what it'd do to the glass. Muriatic acid, like used for cleaning concrete or aluminum, would do the trick.

 

[lctorana]

The irony is that there will be any number of bulbs that come loose in their shells just as soon as you don't need them any more...

I'd try soaking in water. I'd expect that to work, as bulbs often come loose in damp conditions.

If that doesn't work, try metho. And then turps, and finally ammonia.

 

[PhotonWrangler]

Thanks for the suggestions guys. I'll try heat first and then the solvents. If I have any success I'll post the results of the finished product.

 

[scott.cr]

I don't know if this suits your purposes, but when I was a kid I read in an electronics project book from the 1950s how to disassemble a light bulb, and it worked for me.

You score the glass where it meets the metal base, score all the way around the circumference of the bulb. Heat up your soldering iron and touch the tip into the score. I've had the base simply pop off when heated, but sometimes I had to heat all the way around the score. Works like a champ. I used the point of a ceramics drill bit to score the bulb.

 

[Mednanu]

...Heat up your soldering iron and touch the tip into the score. I've had the base simply pop off when heated, but sometimes I had to heat all the way around the score....

I like the idea ( and have heard of similar variants on the theme which have worked well the past ), but please wear some wrap around goggles and something along the lines of a disposable painters suit. It could take hours trying to 'decontaminate' yourself from near-microscopic glass shards if the bulb shattered ( rather than just cleanly cracking/breaking ) while being heated.
Been there; done that - it's simply no fun.

 

[jzmtl]

Edit: If you don't need the electrical contacts intact, a strong acid would take the metal right off, but I don't know what it'd do to the glass. Muriatic acid, like used for cleaning concrete or aluminum, would do the trick.

Acid won't hurt glass one bit.

I've seen low quality light bulb's metal base come off on it's own, maybe look for one of those.

 

[Empath]

Acids will etch glass.

 

[jzmtl]

The etching is not because of acid per se, it's due to the presence of fluoride, and hydrogen fluoride is often used.

 

[65535]

jzmtl, strong acids etch glass, hydrofluoric acid is used to etch glass, what you have is probably well diluted.

There was a cool video on youtube, you take a string soak it in alcohol (small twine about 1/16th - 1/8th inch, wrap it tightly around teh point you want broken, fill the bulb with water up to right under the string, geta bucket of water, light the rope, let it burn for a bit, when it's nearly burnt out, quickly cool it in the water, the top if not already removed, should easily just snap right off. Worked on a coke bottle, either it's harder to break small glass or it easier, but it's worth a shot right? Soaking it in mineral spirits SHOULD work.

 

[jzmtl]

I know acid doesn't react with silica but can't recall the chemical reaction of etching, so I googled it, it's the flouride that's doing the work, not acid.

 

[TigerhawkT3]

If you don't mind shredding the base, you might try Dremeling it off with a cutting disc. :shrug:

 

[Empath]

Jzmtl, it's probably not a simple matter. Hydrofluoric acid will etch glass. Nitric acid can't be contained in plastic. Probably claiming "acid won't hurt glas one bit" is a stretch, as would be my general statement "acids will etch glass". I'm thinking trying to eat away the metal base is not the way to go.

 

[jtr1962]

Buy Satco brand. We've had a good number of that brand where the bulb actually detached from the base as we were changing it, leaving the base stuck in the socket to be removed by "other means". Come to think of it, any oddball brand you get at a dollar store will probably "perform" similarly.

 

[PhotonWrangler]

Hmm, I'll look at those off-brands as a possible source. I tried opening one of the name-brand bulbs and it's probably made to better standards than the knock-offs are.

The scoring-the-glass method also sounds interesting, although I'm not sure how I'd reassemble it once I cut it off at the base.

I wish I could just purchase some 'blanks,' but I doubt I could get those in small quantities.

Thanks again for the suggestions everyone! :thumbsup:

 

[UncleFester]

jzmtl, strong acids etch glass, hydrofluoric acid is used to etch glass, what you have is probably well diluted.

There was a cool video on youtube, you take a string soak it in alcohol (small twine about 1/16th - 1/8th inch, wrap it tightly around teh point you want broken, fill the bulb with water up to right under the string, geta bucket of water, light the rope, let it burn for a bit, when it's nearly burnt out, quickly cool it in the water, the top if not already removed, should easily just snap right off. Worked on a coke bottle, either it's harder to break small glass or it easier, but it's worth a shot right? Soaking it in mineral spirits SHOULD work.

The only catch here is that the light bulb is sealed to keep in the inert gas or vacuum in that allows the bulb to operate.

 

[65535]

I am under the impression that he got the filament out and undid the purging and sealing that was done. I could be wrong but that's what I thought he had done.

 

[Burgess]

i would certainly like to see photos of the individual components.


Especially the filaments.


Good luck in your quest, PhotonWrangler. :twothumbs

_

 

[Illum]

Probably claiming "acid won't hurt glas one bit" is a stretch, as would be my general statement "acids will etch glass".

I agree, you kinda have to keep in mind theres various forms and make of glass...some will react and some doesn't...

 

[PhotonWrangler]

For what it's worth, the glass on the bulb I'm working with seems a little thinner and more brittle than usual. I was able to chip away at some of the small glass shards inside of the base with very little trouble at all. I guess they don't make them like they used to!