Friday 27 July 2012

STEP by STEP make your own DIY light bulb

This has to be one of my all time favourite science experiments!  


It's much more fun than the basic light bulb circuit.  It took me a while to perfect but, with the help of some bods at Maplin in Ipswich and a little patience, I managed it and here's how it's done -

You will need

  • Some fireproof paper/card - I used a bit of egg box carton and made it fireproof (Click here to see how to do it)
  • A red test lead and a black test lead with crocodiles (this makes it easier to set up)
  • a LARGE glass jar ( we used a large Nutella jar for ours)
  • Electrical tape
  • Pencil lead (It's made of graphite these days so don't worry)
  • 7 D size alkaline batteries of a decent quality

What you will need to do:


First attach one of the red crocodile clips and one of the black crocodile clips to your fireproof paper using your electrical tape like this:

You will have to be careful to line everything up as the pencil lead will snap easily so everything needs to be straight. 


Using electrical tape tape together your 8 D batteries positive touching negative:

Remember: the positive side is the side with a bump and the negative is the side that is flat.


Then carefully put the pencil lead in between the two crocodile clips so it looks like this:


Next  you will need your glass jar.  Carefully put it over the filament you've made like this:

The reason we use a jar is to reduce the amount of oxygen around the filament to avoid combustion.  You can use a lighter to burn most of the oxygen out of the jar before placing it over the filament.  This will make it less likely to smoke so much.

In bulbs argon is used to fill the bulbs up because it is an inert gas, a noble gas.  This is also to protect the filament from oxygen reaching it and combustion to occur.


Now connect the red crocodile clip to the positive side of the battery and the black to the negative.  You might want to do what we did and buy ones with crocodile clip protectors on as things do get rather hot!


And there you have it you've made your own light bulb!  I hope you all find this as exciting as we did!  

The reason why this works is because the granite is a conductor of electricity but as the electricity from the batteries run through the wires it produces heat and the granite gets hot and burns until it burns right through.

The filament - our pencil lead - breaks apart, this breaks the circuit, much like in a fuse and that's why the light goes out and it will then need a new filament but be careful!  Everything will be hot!


  1. An excellent experiment, I can remember doing stuff like this in school, hands on science is the best way to learn, schools don't seem to do much like this anymore, too worried about health and safety no doubt.

    Great post :-)

    1. Thank you Techno-Mole! I remember nothing like this at school, but no doubt you are right about health and safety. Well, that and funding.

      Thanks again :D

  2. granite! mmm I think you mean graphite, Lisa!! You could link this to chemistry and talk about the different bonding in graphite and diamond which does not conduct as there are only three bonds in graphite leaving one free electron whereas in diamond all four bonds are used so no free electrons.

    1. Thanks I put Graphite at the beginning! D'oh. That'll teach me for working int the early hours of the morning!

      Thanks for the Chemistry tip!

  3. I'm surprised to see at this age that cute kid has created such amazing DIY light bulb project. She is very talented and no doubt in the future she will make more big projects.

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