What it shows
Cotton and wool fibres absorb a lot of water, while nylon and polyester absorb little. By weighing identical fabric squares before and after soaking, you find which fabric is best for towels and which for raincoats.
The science
Natural fibres like cotton and wool have many tiny gaps and chemical groups that attract water, so they hold a lot. Synthetic fibres like nylon and polyester repel water and hold it only in the spaces between threads. The thickness and weave of the fabric also decide how much it can store.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- 10 cm squares of cotton, towel cloth, nylon, polyester and wool from old clothes
- A bowl of water
- A kitchen scale (to 1 g) or letter balance
- A clip or tongs
- A cloth for drying hands
- A notebook
- A pencil
Safety
For this project: Use old, clean cloth only. Wipe up spills so no one slips, and wash hands after handling the wet cloth.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Cut each fabric into a 10 cm square and label it.
Weigh each dry square and note its weight.
Dip each in the bowl for one minute so it is fully wet.
Lift it out with the clip and let it drip for thirty seconds.
Weigh it again and calculate the water absorbed by subtraction.
Divide by the dry weight to compare fabrics fairly as grams of water per gram of fabric.
Make a bar chart ranking the fabrics from best to worst absorber.
What you should see
Towel cloth and wool take up the most water per gram, cotton comes next, and nylon and polyester take up the least. The ranking explains why towels are cotton and raincoats are nylon.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Why is towel cotton?
Cotton fibres absorb a lot of water.
2Why is a raincoat nylon?
Nylon repels water.
3Why divide by dry weight?
To compare squares that are not the same weight.
4What does the loop of towel thread do?
It adds space and surface area that hold water.
Take it further
Measure how long a drop of water takes to soak into each fabric.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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