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Technologies K–10 · Years 3–4

Which fabric makes the best sun hat: testing with UV-sensitive beads

Material World (NSW Science and Technology K–6, 2017); Design and Technologies: Processes and production skills, Investigating and defining (ACARA v9)

PracticalLow risk

The idea

Fabrics differ in how much ultraviolet (UV) radiation they let through, and UV-sensitive beads that change colour in sunlight show which fabric protects skin best.

What you need

  • 30 UV-sensitive colour-change beads (white indoors, coloured in sunlight)
  • 6 opaque paper cups (or clear cups wrapped around the sides with aluminium foil) and 6 rubber bands
  • 5 fabric squares 15 cm × 15 cm: cotton T-shirt knit, denim, loose-weave cotton gauze, polyester sports mesh, and a fabric from a garment with an ARPANSA UPF 50+ swing tag
  • A colour score chart from 0 (white) to 4 (deep colour)
  • 1 stopwatch reading to 1 s; a sunny day with the school's sun protection routine in place

How to do it

  1. Put 5 beads in each cup. Leave one cup uncovered and cover the mouth of each of the others with one fabric held by a rubber band, so that UV reaches the beads only through the fabric.
  2. Predict the order of the fabrics from most to least protective.
  3. Carry the cups outside in a closed box and set them upright side by side in full sun, still covered by the box.
  4. Find the exposure time first: lift the uncovered cup into full sun with the others still covered, and time how long its beads take to reach the deepest colour on the chart, score 4. Return that cup to the shade until its beads are white again.
  5. Uncover all 6 cups together for that same time, cover them, return to the shade, then lift each fabric in turn and score the bead colour against the chart straight away.
  6. Bring the beads back indoors until white again, then repeat the test with the same exposure time.
  7. Agree criteria for a class sun hat (UV protection from the test, comfort, and whether the fabric can be reused or recycled), rank the fabrics against them and choose one, giving the test result as evidence.

What you should see

Beads in the uncovered cup reach the deepest colour, score 4, because the exposure is timed from that cup. Beads under the UPF 50+ fabric and the denim stay white or faint; beads under the gauze and the mesh sit between. The UPF number is the factor by which a fabric cuts the ultraviolet radiation reaching the skin (AS/NZS 4399), so UPF 15 lets through 1/15 of it (6.7%), UPF 30 1/30 (3.3%) and UPF 50 1/50 (2.0%), stopping 93.3%, 96.7% and 98.0%; ARPANSA classifies UPF 15 as minimum, 30 as good, and 50 or 50+ as excellent protection. The cup walls must be opaque: through clear plastic walls, sunlight and UV from the sky reach the beads without passing through the fabric, and every cup colours. The exposure is timed rather than set at some number of minutes because the beads stop deepening once they reach the top of the chart: an exposure long enough to saturate the beads under a loose weave leaves every cup reading 4 and the fabrics cannot be separated, which is why the time comes from the cup that colours fastest. The beads rank fabrics; they do not measure a UPF value. The learner knows it worked when the uncovered cup is darkest, the UPF 50+ cup is palest, the five fabrics fall in an order, and that order repeats in the second trial.

What changes

What you change
the fabric covering the cup
What you measure
the bead colour score (0 to 4)
What you keep the same
  • 5 beads per cup
  • the same exposure time for every cup, timed from the uncovered cup
  • cups side by side
  • scored straight after exposure
  • opaque cup walls, so UV reaches the beads only through the fabric

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • Any fabric stops sunburn (loose weaves let a lot of UV through).
  • Thin white fabric protects as well as thick dark fabric (weave, thickness and colour all change protection).
  • You cannot get burnt on a cool or cloudy day (UV, not heat, causes sunburn).

Safety card

Low riskLearners carry it out

Hazards

  • Sun exposure outdoors
  • Small beads are a choking hazard

Controls

  • Hats, sunscreen and shade under the school's sun protection policy; the cups are set out, uncovered for the timed exposure and collected, and learners stand in the shade between readings
  • Beads stay in cups and are counted back in

Note

No chemicals or heat. Record the activity on Primary School RiskAssess (riskassess.com.au).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Science and Technology K–6 Syllabus (2017), NESA. The syllabus taught in 2026; the 2024 syllabus replaces it from 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.ST2-7MW-TST2-8PW-STST2-2DP-T
  • Science and Technology K–6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST2-DDT-01
  • Australian Curriculum v9AC9TDE4P01AC9TDE4K02AC9TDE4P04

Sources

The pages the author read to write this activity.

  1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
  2. curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
  3. www.arpansa.gov.au/our-services/testing-and-calibration/ultraviolet-radiation-testing/fabric-testing
  4. www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/sun-protection-clothing
  5. primaryconnections.org.au/teaching-sequences/year-4/packaging-pioneers/lesson-5-combining-materials

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