The Zap Audit: Turning Winter Static into a Fair Test at Bolitho

On a cold November morning, the first person through the main corridor often announces themselves with a small crack from a door handle. At Bolitho, those winter zaps have become the starting point for a pupil-led investigation into static electricity. Rather than treating the shocks as a nuisance, a group of pupils in the science club has begun a structured survey of fabrics, surfaces, footwear and indoor humidity. Their aim is not to eliminate every spark, but to understand why some combinations produce more charge than others — and to turn a familiar seasonal irritation into a fair, repeatable experiment.

Why Winter Brings More Sparks

Static electricity is the build-up of electric charge on a surface. When two materials are pressed together and separated, electrons can transfer from one to the other. Some materials give up electrons readily; others hold them. In a classroom, walking across a carpet in rubber-soled shoes, pulling on a woolly jumper, or sliding a coat from a chair can all separate materials that have been in contact. If the charge cannot flow away, it accumulates. A subsequent touch — especially of a metal door handle or a metal chair frame — can allow a rapid transfer, which we feel as a shock.

The effect is often stronger in winter because indoor air is drier. Heating warms the air, and although the absolute amount of water vapour may not change much, the relative humidity falls. Moist air can help charge leak away across surfaces; dry air allows it to linger. Cold outdoor air also holds less moisture, so ventilation with cold air can lower indoor humidity further. The result is a classroom environment in which charge builds more easily.

Designing a Fair Test

The pupil group began by agreeing that a survey of random shocks would not be enough. Anecdotes from classmates — my jumper always zaps me, or the door handle is worse on Mondays — are useful starting points, but they are not evidence. The team therefore designed a small bench test with clear variables.

The independent variable is the material combination under test: fabric type, surface type or footwear sole. The dependent variable is a simple proxy for charge: the number of small paper confetti pieces attracted to a charged object, or the distance at which the charged object begins to attract them. Control variables include the size of the fabric square, the number of rubs, the pressure applied, the person carrying out the test, and the time between charging and testing. The team also records relative humidity and room temperature for each trial, because these conditions may change the result.

This is not a perfect measurement of charge in coulombs. It is a comparative test, and that is appropriate for a school investigation. The pupils are learning that a fair test depends on holding conditions constant and changing one factor at a time.

The Test Bench: Fabric, Surface and Footwear

The first round compares three fabric squares — wool, cotton and a polyester fleece — rubbed against a plastic ruler. Each square is rubbed ten times over the same length of the ruler, using the same hand pressure. The ruler is then brought slowly towards a shallow dish of paper confetti, and the distance at which the first pieces jump is recorded in millimetres. The test is repeated five times for each fabric, with the ruler discharged between trials by touching it to a metal sink tap. This simple step prevents charge from carrying over from one test to the next.

A second station looks at surfaces. Pupils use a charged plastic rod and bring it near to a range of materials found around school: a carpet tile, a vinyl floor sample, a wooden bench and a metal cabinet. The question is not whether the surface itself becomes charged, but how charge behaves when it is nearby. Metal surfaces allow charge to move easily, which is why a door handle can deliver a sharp shock; insulating surfaces such as carpet may hold charge locally.

A third station examines footwear. Pupils compare rubber-soled trainers, leather shoes and wellington boots by standing on a carpet tile and then touching a metal plate connected to a simple electroscope. The aim is to see whether sole material affects the charge transferred to the person. This station requires careful supervision, because it involves pupils and metal. No mains equipment is used, and the metal plate is isolated from sockets and computers.

Reading Humidity Without Guesswork

The group borrowed a digital hygrometer from the science store and recorded relative humidity at the start and end of each session. This matters because a result collected on a dry day may not be comparable with one collected after rain. The pupils also noted whether the heating was on and whether windows had been opened. Over several weeks, they hope to build a picture of how classroom conditions change the strength of the effect.

The team is careful not to overclaim. A single afternoon of tests cannot explain every shock in the school. But repeated measurements, taken under similar conditions, can reveal patterns. That is the difference between a science survey and a collection of stories.

Safety and Sensible Boundaries

Static electricity investigations are low-risk when handled sensibly, but the group has set clear boundaries. Pupils do not use mains electricity, do not test near sockets or computer equipment, and do not rub materials against their skin. Metal rulers are avoided in favour of plastic ones. Anyone with a sensitive electronic device, such as a hearing aid or a pacemaker, is not asked to take part in the footwear station. The group also checks that no one has a skin condition that could be irritated by repeated rubbing of fabrics.

These precautions are part of the investigation, not an afterthought. Good science includes thinking about risk before starting.

What the First Round Suggested

The early results have been deliberately modest. The pupils have observed that the polyester fleece and wool squares tend to produce a stronger attraction than cotton in the same conditions. They have also seen that the effect varies from day to day, which has prompted a useful discussion about humidity and heating. Rather than declaring a winner, the group is now planning to repeat the tests across different rooms and times of day.

This is a valuable lesson in itself. A result that changes with conditions is not a failure; it is a clue. The next stage is to record humidity more consistently and to test whether the same fabric combination behaves differently in a heated classroom and a cooler corridor.

Taking the Audit Home

Families can repeat a simplified version at home with a balloon, a woollen jumper and small pieces of tissue paper. Rub the inflated balloon on the jumper for ten seconds, then hold it near the tissue pieces and note the distance at which they are attracted. Try the same test with a cotton sleeve and compare. Record the room conditions — heating on or off, window open or closed — and repeat on another day. The aim is not to produce a definitive answer but to practise fair testing.

A simple table with columns for material, number of rubs, distance and room conditions is enough. Pupils can bring their results back to school to add to the class display.

Beyond the Zap

The zap audit is a small investigation, but it connects to larger ideas: charge, insulation, conductivity and the way we control indoor environments in winter. It also gives pupils a reason to look closely at ordinary moments. A shock at a door handle is no longer just a surprise; it is a question about materials, moisture and measurement. At Bolitho, that is exactly the kind of question the science hub exists to encourage.