These pumpkin lava lamps for Halloween are a fun party activity or decoration and an unusual alternative to a traditional pumpkin. They are super easy to make and entertaining to watch, especially in the dark.
Other ideas are to try different colours, add glitter, or get creative and decorate the jar to look like a witch or ghost.
How to make a pumpkin lava lamp
You will need
- A clear plastic bottle or jar
- A bottle of vegetable oil
- Orange food colouring
- Glitter
- Water
- Alka Seltzer
- Black pen and pipe cleaners for decoration
Lava Lamp Instructions
Fill the bottle or jar a quarter full with water, add a little orange food colouring and mix well.
Top up to the (near) top with the vegetable oil.
The oil and water will separate into two layers. Water at the bottom and oil at the top.
Decorate as you wish, we used a black whiteboard pen for the face.
Drop half an Alka-Seltzer tablet into the jar and watch what happens.
How do lava lamps work?
Polarity – Why they don’t mix
Water is a polar molecule. This means it has a slightly positive charge on one end and a negative charge on the other. Because opposite charges attract, water molecules cling tightly to each other. Oil is non-polar, meaning its charge is evenly distributed. Since oil molecules aren’t attracted to water (they are hydrophobic), they separate into their own layer.
Density – Why oil sits on top
Oil is less dense than water, which makes it float on the top of the water layer.
Chemical Reaction
 Alka-Seltzer tablets contain citric acid and sodium bicarbonate. When the tablet is added to water, it dissolves, and a chemical reaction occurs that creates carbon dioxide gas and sodium citrate. As the carbon dioxide bubbles rise, they carry hitchhiking droplets of coloured water through the oil layer to the top. Once the bubbles burst at the surface, the dense water droplets sink back down, creating the classic lava lamp effect!
More Halloween Science Experiments for Kids
Our spooky lava lamps look great, too!
Try one of my great Halloween Science Experiments, including jumping ghosts, a spooky noise maker and fake blood.
Or how about giving one of our spooky Halloween STEM challenges a go?
Last Updated on October 22, 2026 by Emma Vanstone
They are so cool I love them. We’ve been decorating pumpkins too.
Very cool (and original)! I think we may try it at half term. x
I have loads of jars the girls can use to make these.This will be great for a half term activity next week.
Great idea for children. Simple enough to do with kids and cost effective! Thanks for sharing.