HowTo: "Coring" light bulbs

Some articles have already pointed out that old light bulbs can easily be given a new “lamp life”. In almost all cases, the filament, its holder and parts of the threaded base must be removed.

How you can do this is described in the following article.

Safety instructions

I know the following notes are always kind of annoying and seem unnecessary. Unfortunately, many people who knew "better" have lost eyes, fingers or other things due to carelessness or injured themselves. Data loss is almost negligible in comparison, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Because even the coolest project is not worth injury or other trouble.

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Required material:

In the following list you will find all the parts you need to implement this article.

Required tool:

In the following list you will find all the tools you need to implement this article.


Especially with work like this, it is even more imperative to pay attention to safety! It is very likely that one or perhaps several bulbs will break during the first attempts. For this reason, it is imperative that sufficient thick gloves, a Garment that covers the arms and a Safety goggles an.

Please be conscientious and careful at work and do not join the ranks of people who say today “Oh, if only I had invested five seconds back then to take safety precautions”.

This is what your safety gear might look like, for example. Also make sure to wear a top with long sleeves. This is the only way to protect your forearms against flying glass splinters.

Remove foot contact

The only sensible way into the glass body of an incandescent lamp is via the screw contact. This also contains the two contacts through which the energy is supplied to the incandescent lamp. These are called the ring contact and the base contact. Of these two, the foot contact can be removed relatively easily and thus allows access to the glass body.

The light bulb to be “cored”.
The foot contact is on the bottom. With a...
...side cutter or to also a knife its edge can be bent up and thus...
the whole foot contact pull out and...
...remove. What remains is a black ring which is also made of (black colored) glass.
This can be easily cut into individual parts with the side cutter and thus carefully broken out.
The remaining fragments of the black glass ring can then be shaken/knocked out of the base of the lamp relatively easily.
Detailed view of the bulb after removing the foot contact.
Detailed view of the bulb after removing the foot contact.

Remove the lower part of the glass bulb

After the foot contact is removed, it is relatively easy to get to the bottom of the glass bulb.

You can break out the lower end of the glass bulb relatively easily with needle-nose pliers.
Detailed view after removal of the lower part of the vitreous body.

Pierce vitreous body

Now comes the most critical part. Now you have to break a first hole into the glass body with a screwdriver.

The best way to do this is to use a small screwdriver to very carefully press the glass body in. Make sure that you do not break through the entire glass body as soon as the first resistance falls away.
If you have pierced the inner part of the glass body, it might look something like this.
Detailed view of the pierced vitreous body.

Increase implementation

After you have pierced the glass body, you can now enlarge this hole with a screwdriver.

Carefully break out the individual pieces. Again, make sure to remove only the remnants of the glass body in the screw base.
Detailed view of the exposed screw base.


Removal of the last glass fragments.

The work must have caused a few pieces of glass to get into the interior of the bulb.
The easiest way to remove them is to fill the lamp with water and rinse out the glass splinters.
This also temporarily makes the milky glass of the bulb almost clear.
Detailed view of the cleaned bulb.


By the way, this procedure also works with other bulb shapes 🙂 .

Have fun with the project

I hope everything worked as described for you. If not or you have questions or suggestions please let me know in the comments. I will then add this to the article if necessary.
Ideas for new projects are always welcome. 🙂

PS Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you think it's cool that I share the information with you, I would be happy about a small donation to the coffee fund. 🙂

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