Do you like to dunk a biscuit in a hot drink or a glass of milk? Do you find some biscuits are better for dunking than others? Personally, I’m a big fan of the chocolate digestive to dunk. The combination of melted chocolate and soft biscuit is the best!

What makes a good dunking biscuit? Do you like to dunk a biscuit more than once, or do you prefer one dunk to give the perfect melty texture?

We designed an investigation to find out which type of biscuit is best to dunk. Everyone can probably agree that a biscuit breaking and landing in the drink is never a good thing, so we placed six different biscuits in hot water and timed how long each took to collapse.

We chose to test typically British biscuits, but you can use any type you want.

Biscuit dunking science investigation

collage of different biscuits for a biscuit dunking investigation

You’ll need


Transparent cups

Different types of biscuits

Warm water

Measuring cup


Carefully pour the same amount of warm water into each cup.

Place a biscuit in each cup and start the timer. If the biscuits are too wide, snap them in half. Each biscuit should touch the bottom of the cup.

Start the timer and record how long it takes for each biscuit to collapse.

Biscuit dunking experiment

Another way to do this is to place each biscuit on a separate plate and drop the same amount of water onto each. Weigh the biscuit before adding water and again five minutes after adding water. The biscuit that absorbs the most water will be the one most likely to fall into your drink.

I’ve created a biscuit dunking challenge investigation sheet for recording results and writing up the investigation.

Biscuit dunking challenge experiment write up sheet
Biscuit dunking challenge experiment results recording sheet

Which is the best biscuit to dunk?

We found the shortbread biscuit could be dunked the most number of times without breaking and was the last biscuit to collapse in the cup of water test.

So, if you want a sturdy biscuit that can be dunked more than once, choose a shortbread-style biscuit.

Extension tasks

Repeat the activity using cold water and compare the times with hot water.

If you enjoyed this activity, take a look at my other delicious edible experiments!

Last Updated on March 11, 2024 by Emma Vanstone