Halloween chemistry Elephants Toothpaste

The spooky season of Halloween is an wonderful opportunity to end the Autumn term with a Halloween themed Chemistry demonstration.  This would be exciting to carry out (as a trick or a treat) using the Elephant’s Toothpaste reaction with a Halloween twist!

You will need 

A large pumpkin (from the supermarket) 

Implements to scoop out the insides of and to carve your pumpkin safely      

Safety goggles

Nitrile gloves

Black bin bags    

250ml narrow mouth conical flask

A funnel – to fit in the conical flask

100ml beaker

Hydrogen Peroxide (100vol – 30mls) and CLEAPSS Hazcard 50

Potassium Iodide crystals (2g – pre-weighed in a labelled vial or test tube) and CLEAPSS Hazcard 47B

Washing up liquid (~2mls)

Food dye or chromatography ink (optional: ~2-3mls)

2 x disposable plastic pipettes

Large bucket (for disposal)

How to do the Elephants Toothpaste experiment 

  1. Buy a pumpkin (or several if you want to repeat the demonstration for multiple classes) from your local supermarket a day or two before the experiment.  These are usually readily available from the end of September. We suggest, as always, that you trial this demonstration before conducting it in front of your class.
  2. Cut a hole in the top of the pumpkin, so that the top can be removed like a lid and discarded.
  3. Scoop out the insides of the pumpkin and cut a hole in the base of the pumpkin which is large enough to accommodate the base of the 250ml narrow mouth conical flask you are going to use (to ensure the flask is flat on the desk during the demonstration).  Discard the insides and base.
  4. Carve a face into the front of your pumpkin, cutting out holes for the eyes, nose and mouth. Some of the ‘toothpaste’ will flow out of the mouth of your pumpkin, so the mouth needs to be carved low down on the front of the pumpkin.
  5. At the time of the demonstration, completely cover the desk with a black bin bag. Cut the bag open to increase its surface area, to cover and protect as much of the desk surface as possible.
  6. Ensure the students that are watching are standing at a safe distance away from the demonstration.
  7. Wearing your safety goggles & nitrile gloves, measure out 30mls of 100vol Hydrogen Peroxide into the 100ml beaker and, using a funnel, pour this into the 250ml conical flask, taking care to make sure the Hydrogen Peroxide does not come into contact with the neck of the flask.  
  8. Using disposable pipettes, add a small amount of washing up liquid (~2mls) & the optional food dye (~2-3mls, any colour you like) and give the flask a gentle swirl to mix the contents well.
  9. Place the pumpkin onto the middle of the covered bench area and place the conical flask inside, checking that the flask is flat and stable on the desk surface through the hole in the bottom of the pumpkin.
  10. Next, carefully empty the vial or test tube containing 2g of Potassium Iodide into the conical flask inside your pumpkin & immediately step back from the demonstration. 
  11. Students can watch as steam and foam rise out of the pumpkin’s head and eventually some should spill out from the pumpkins mouth.

The Science behind the Elephants Toothpaste experiment

The Elephant’s Toothpaste reaction demonstrates the rapid decomposition of Hydrogen Peroxide.  The reaction is catalysed by Potassium Iodide.

The Iodide ions attract the oxygen in the Hydrogen Peroxide.  This breaks the molecular bonds and turns the Hydrogen Peroxide into water and Oxygen gas.  The Oxygen is trapped in the washing up liquid forming bubbles and foam. 

The reaction is exothermic, and steam is produced.

Risk assessment 

Usual care should be taken when using carving implements to carve your pumpkin.

Safety goggles and nitrile gloves should be worn throughout the demonstration.

CLEAPSS literature should always be consulted before carrying out any practical or demonstration.  The CLEAPSS Risk Assessment for the Elephant’s Toothpaste Demonstration can be found here:


The demonstration should be trialled before performing in front of a class.

Observers should be at a safe distance away.

Clean up and disposal

In order to dispose of your pumpkin safely afterwards, wear gloves and goggles to collect it into the bin bag used to cover the desk.

Place everything into a large bucket of water in order to rinse off and dilute any remaining Hydrogen Peroxide. 

Once the pumpkin and binbag have been thoroughly rinsed off, they can be placed into the normal waste and the remaining bucket of water can be poured down the foul water drain, flushing away with further water.  

Ensure no traces of Hydrogen Peroxide are left on the work bench area. 

Get advice about the Elephants Toothpaste Halloween experiment

If you have any questions about setting up the Halloween themed Elephants Toothpaste experiment, please contact our Technical Support Team via techsupport@philipharris.co.uk