Science fair: How many fibres come off our clothes in a wash? (ages 11–16)

The question

• How many fibres come off our clothes in a wash, and does the fabric or the wash setting change it?
• Ages 11–16. Time: two sessions (a wash, then counting). Made and funded by No Plastic Today. Licence: CC BY 4.0.

Why it matters

• Synthetic fabrics (polyester, acrylic, nylon) shed tiny plastic fibres every wash. Scientists find fibres everywhere they look: in 102 out of 102 sea turtles examined across three oceans, fibres were the most common type of particle (Duncan and others, Global Change Biology, 2019: doi.org/10.1111/gcb.14519), and in 50 out of 50 stranded whales, dolphins and seals around Britain, 84% of the particles were fibres (Nelms and others, Scientific Reports, 2019: doi.org/10.1038/s41598-018-37428-3).

Hypothesis

• Example: "A fleece will shed more fibres than a cotton T-shirt, and a hot, long wash will shed more than a cool, short one."

Variables

• Independent variable: fabric type (100% polyester fleece; 100% cotton T-shirt; a 50/50 blend), OR wash setting (30 degrees short cycle versus 60 degrees long cycle) — test one at a time.
• Dependent variable: mass of fibres captured (mg) and, optionally, fibre count under a hand lens or microscope.
• Control variables: same machine, same detergent and dose, same load size, garments washed the same number of times before the test (fibre shedding is highest on new clothes), same filter paper.

Materials

• Washing machine with a hose you can direct into a bucket, OR a large bowl for a controlled hand wash (5 litres of water, 100 rotations by hand; more consistent for younger students).
• Coffee filters or laboratory filter paper (same brand throughout), a funnel and a jug.
• Scale accurate to 0.01 g (a jeweller's scale, about 10 pounds/dollars) or the school lab balance.
• Hand lens or school microscope; a dark card for contrast.
• Labelled zip bags for dried filters.

Method

• 1. Weigh a dry filter paper and record its mass.
• 2. Wash one garment per test in the controlled bowl (or run the machine and collect the outlet water in a bucket).
• 3. Pour the wash water through the funnel and filter, in stages. Rinse the bowl with 500 ml of clean water and pour that through too.
• 4. Dry the filter flat, overnight, away from dust. Reweigh. Fibre mass = final mass minus starting mass.
• 5. Under the hand lens, count fibres in three 1 cm squares and multiply up for an estimate of total fibres.
• 6. Repeat each condition three times. Use fresh filter paper each time.
• 7. Optional: wash the same fleece five times and plot fibre mass per wash to see whether shedding drops as the garment ages.

Results table (columns)

• Garment or setting | Filter mass before (g) | Filter mass after (g) | Fibre mass (mg) | Fibre count estimate | Notes (colour, length)

Analysis questions

• Which condition shed most? By how many times?
• If your household does four washes a week, what is the estimated mass of fibres per year from this garment type?
• What three things could a household change tomorrow (wash cooler and shorter; fill the machine; a fibre-catching bag or filter; choose natural fibres)?
• What could a washing-machine maker change? (Some countries are discussing built-in filters; check the latest news for your country.)

Safety

• Hot water: keep below 45 degrees for hand washes. Detergent: gloves and eye protection when handling neat. Do not put filters in a food oven to dry.

Curriculum links

• England: KS3 Science "working scientifically"; KS3 Chemistry (Earth as a source of limited resources); General Certificate of Secondary Education (GCSE) Biology (human impact on ecosystems). Design and technology (D&T) Textiles.
• Next Generation Science Standards (NGSS): MS-ESS3-3 (design a method for monitoring and minimising a human impact); MS-LS2-4; HS-ESS3-4.
• Australian Curriculum v9: Science Inquiry Years 7–10 (verify codes); Design and Technologies 7–10 (materials).
• International Baccalaureate (IB) Environmental Systems and Societies (ESS) internal assessment angle: fibre release versus wash temperature as a pollution-management question.