In this activity, learners make pykrete by freezing a mixture of water and a material like cotton wool, grass, hair, shredded paper, wood chips, or sawdust. Learners discover that pykrete has some interesting properties, since compared to normal ice it melts slowly and is much stronger and tougher. Use this activity to talk about the advantages and disadvantages of different types of materials. Notes: Since pykrete will melt, testing should be done outdoors. Video is not available in the US, but it is not needed to understand how to do the activity.