Window Clings

Make window art whilst demonstrating the science of crosslinking and also diffusion – two experiments in one!

You will need:

Gelatine or agar agar (one packet should be enough)
Boiling water
Biscuit cutters
Food colouring
Cocktail sticks or a skewer
A straw
Baking tray or fridge-proof dish
Kitchen roll

How to make them

Add gelatine or agar agar powder to boiling water (get an adult to help you) Follow the instructions to make a firm jelly. Stir well until dissolved.  Place in a tray or dish.  Allow to cool and place in the fridge to set.

Once set, use biscuit cutters to cut out shapes in the firm jelly, peel away the excess gelatine from the shapes.  Using a straw make holes in your shapes and using a cocktail stick or skewer (be careful) pick out the plug of gelatine from the hole.

In the holes in the jelly add some drops of food colouring.  Watch over the next few hours as the food colouring spreads to colour the jelly shape.

Remove the shapes from the tray with a spatula and gently dab them with kitchen roll to take off any excess food colouring.

Place the shape on a window.  Over the next few days watch the shape change as the water evaporates and it dries out.  Place the shape back into a tray of water and watch it become flexible again and place on your window.

The Science Bit:

Cross Linking

We made the window clings by using gelatine (or agar agar) to transform the water (a liquid) into a gel (a solid).

Find out more about cross-linking in one of our other experiments – Store cupboard science for the festive season – bioplastic decorations! – Chilled Education

Diffusion

The window cling gel can still absorb liquid, which we showed by adding the food colouring into the holes in the clings and watching the colour move from the hole to across the whole of the window cling shape.

How does this happen? This is due to ‘diffusion’ – this is where molecules move from areas of high concentration to areas of low concentration.  This can also be seen in our growing jelly babies and growing gummy bear experiments Store cupboard science – the sweet treat edition! Making ice cream, growing jelly babies and rainbow skittles – Chilled Education.

The Window Cling is mostly made of water, so the heat of the sun or the warmth of your room as the window cling is on the window causes the water to evaporate, which makes it thin, drier to the touch and less flexible. It will eventually crack, but if you add the cling to water again it will absorb the water and go back to a gel state, and can then be stuck back on the window.

Even better, when you have finished with your window cling it can go into the food waste recycling bin or, if it’s vegetarian gelatine, the compost bin.

To find out more about osmosis and diffusion visit: Comparing diffusion, osmosis and active transport – Transport in cells – Edexcel – GCSE Combined Science Revision – Edexcel – BBC Bitesize