Question: Ho to make a volcano?

Pete Webb answered on 16 Oct 2025:

Make a cone with builder’s plaster about 10 cm high and 10 diameter at the base. When it’s completely set and hard, make a hole in it from the top down, 1 cm wide and 4 cm deep. Half fill the hole with bicarbonate of soda (NOT baking powder), then spoon in some vinegar. If you can get hydrochloric acid online, mix that half and half with the vinegar first, it makes a more lively eeruption!