Matter & Chemistry · Project 11 of 12

The Cheapest Clean

Which cleaning method is cheapest and best

Five methods already in your cupboard, one stain, one score each, and the rupees every use quietly costs.

The calendar this needs: Fourteen days of baseline logging starting in week one, one bench day of sequential tests with a drying wait on each side of it, then a switched fortnight logged exactly the same way, which leaves week six for the defence.

Six weeksNo equipment on the paper route 20 written stepsMarked out of 20Free forever
The question

Which of five cleaning methods already in your house shifts the same stain best, and what does each one cost per use?

Every claim printed on a cleaning label started as a controlled comparison somebody ran on a bench, and the industry that runs them — formulation, quality control, consumer testing — pays for people who can hold conditions still. A result means nothing without its controls, which is why the same cloth, the same dose, the same water and the same contact time matter more than the product does. Cost per use is how procurement teams in hospitals, hotels and factories actually choose between products, and almost nobody at home ever works it out.

Two acts. Find, then fix.

Every EAD project runs the same shape. The first act produces a number nobody in the room could previously state. The second act changes exactly one thing and proves whether that number moved.

Act 1 · Find
You take one stain that keeps returning in this house, make identical patches on one cloth — three for each method where the cloth stretches to fifteen — and test five methods already in the cupboard, one method at a time in one bowl, under conditions you hold still and write down first. You then measure how much of each product a single test consumed and divide the pack price by the pack quantity, so every method carries a rupees-per-use figure beside its score.

A one-page costed problem statement: the stain, how often it happens, the five methods ranked by removal score out of five, the rupees per use printed beside each score, and the household's yearly spend on its current method at the real stain frequency. The number of patches each method got is printed beside the ranking, so a single run per method is stated as a limit rather than hidden. Beside it sit the patches or their photographs in a row, the written scoring scale, and the dose behind every cost figure.

Act 2 · Fix
The household switches to the winning method for a fortnight, and every stain event is logged exactly as it was logged during the baseline fortnight: item, product, quantity used, rupees, minutes of scrubbing and the score afterwards. Both fortnights are then divided by their two weeks so they can be set against each other.

Two comparisons on the same page, one for each unit — rupees per week and minutes per week, baseline fortnight against switched fortnight — with the mean score achieved, the named confounders, and the household's recorded answer on whether the switch stays.

What actually gets measured

The numberrupees per use to shift one standard stain, and the removal score those rupees buy, in rupees per use, against a removal score out of five
BeforeIdentical patches from one cloth — three per method where the cloth allows, otherwise one per method with that limit printed beside the ranking — carrying the same stain quantity, the same stain age, the same water volume and temperature, the same contact time and the same scrub count, and tested one method at a time in one bowl. A second person then relabels every patch with a fresh random letter and keeps the letter-to-method key away from the three scorers, who each mark it on a written five-point scale without speaking. Quantity used is weighed or counted per test and multiplied by the pack price divided by the pack quantity. Alongside it, a fourteen-day log of what the household spends and scrubs now.
AfterThe same log kept for a fortnight on the winning method — item, product, quantity, rupees, minutes and score for every stain event — with both periods divided by their two weeks, so baseline and switch are compared as rupees per week and minutes per week.
The honest partA well-measured failure scores higher than an unmeasured success. If the number did not move, say so and explain why.

If your household cannot run this

If there is no spare cloth to cut, no scale, no co-operative household, or nowhere at home where cleaning products can be opened safely, the whole method runs on school property with a member of staff. The school's cloth, the school's tap and bowl, the school's own cleaning products with their pack prices and pack quantities, and the school's own stain events logged for the same two fortnights. It is marked against the same twenty points, question for question, as every other folder. It is not a reduced version and it is not marked as one.

Every step, written out

Twenty steps in total — ten to find the number, ten to fix it. Pick the route that matches what your school actually has.

A hand-drawn five-point scale, a traced outline of every patch and squared paper give the same ranking and the same rupees per use; the arithmetic is done longhand in the margin where anybody can check it.
You need: One old cotton item nobody needs, cut into five identical squares, with a pencil for labelling the backs · A quarter-teaspoon or a dropper kept for the project, a measuring jug for water, and a brush kept only for these tests · A watch or timer for contact time, gloves and eye protection, and one bowl used for one method at a time, rinsed and emptied before the next product is opened, so nothing is ever mixed · A notebook ruled into seven columns: method, dose, pack price, pack quantity, rupees per use, three scores, mean · Tracing or greaseproof paper and a sharp pencil for the traced outline of every patch · Squared paper and a ruler for the hand-shaded five-point scale, the counted stain area and the bar charts

  1. Pick the stain

    40 minutes, plus 5 minutes on every day a stain happens across the fourteen-day baseline log
    Choose one stain that keeps coming back in this house and start counting how often it happens.
    • Ask whoever does the washing which stain returns most — cooking oil, tea, ink, turmeric or grease — and write their answer down word for word.
    • Count how many garments or cloths carry that stain right now and draw or list them on the first page.
    • Rule a fourteen-day household stain log with columns: date, item stained, product used, quantity used, rupees, minutes spent, result.
    • Walk to the shelf and copy every cleaning product's name, pack price and pack quantity off its label into the notebook.
    • Write the household's usual method for this stain at the top of the page, in the words of the person who does it.
    Write down: The chosen stain, the count of items carrying it now, the first dated row of the fourteen-day log, and every product with its pack price and pack quantity.
    Finished when: The log has its first dated row and every cleaning product in the house is listed with a price and a quantity copied off the pack.
    Commonest mistake: Choosing a rare, dramatic stain because it looks impressive. The number that matters is rupees per year, and that comes from the boring stain that happens weekly.

  2. Make the patches

    45 minutes, plus the drying hours before any patch is treated
    Cut one cloth into five identical patches and put an identical stain on every one.
    • Take one old cotton item nobody needs and cut fifteen squares of the same size from the same part of it — three for each of the five methods — so weave and colour match across every patch. If the cloth will not stretch to fifteen, cut five, and print that one-run limit beside your ranking later.
    • Apply the stain with the same tool every time — one level quarter-teaspoon, or three drops from the same dropper — to the centre of each square.
    • Stain every patch within the same five minutes, so all of them are the same age when they are treated.
    • Lay the patches flat on a covered surface, number them in pencil on the back only, and leave them the same number of hours to dry.
    • Have a second person relabel every dried patch with a fresh random letter, write the letter-to-method key on a separate sheet, and keep that sheet out of the room until all three scorers have written their numbers down.
    • Lay tracing paper over each dried patch and trace the outline of the stain, then count the squares it covers on squared paper and write that count down.
    Write down: The cloth used, the square size, the number of patches per method, the stain quantity per patch, the time each was stained, the drying hours, and the starting square count for each patch.
    Finished when: Every patch carries the same stain applied within five minutes of the others, each has a traced outline with a counted starting area, and a second person holds the letter key.
    Commonest mistake: Cutting patches from different garments because one square was short. Different weave holds stain differently, and the test then measures cloth instead of method.

  3. Fix the conditions

    45 minutes
    Write the protocol that holds everything still except the one method under test.
    • Write the fixed conditions down before anything is mixed: same water volume in the jug, same water from the same tap, same contact time, same scrub count, same brush.
    • Draw the five-point scale by hand: five shaded reference squares running from unchanged to no stain visible, each labelled in words, and pin it on the wall.
    • Write how a patch gets scored: the three scorers see only the front and the random letter a second person gave it, never the pencil number on the back, and each writes a number alone without speaking.
    • Read every hazard label aloud with the named adult present and agree the rule out loud: one product open at a time, one product per bowl, the bowl rinsed and emptied and the product closed and put away before the next one is opened, and nothing heated.
    • List the five methods, one per row, each with the exact dose it will be given.
    Write down: The protocol as a numbered list, the drawn and labelled five-point scale, the scoring rule, and the five methods with their doses.
    Finished when: Another person could run the whole test from your written protocol without asking you a single question.
    Commonest mistake: Deciding the scale after seeing the results. A scale drawn afterwards always flatters the method you were hoping would win.

  4. Run the tests, one at a time

    90 minutes for one round of five methods — three rounds if you have three patches per method — plus the drying hours before anything is scored
    Treat the patches under identical conditions, one method at a time, and record the result twice over.
    • Test strictly one method at a time in one bowl. With gloves and eye protection on, a window open or the bench outdoors, and the named adult in the room, open one product only, measure its dose, treat its patch, then rinse and empty the bowl, close that product and put it back on the shelf before the next one is opened. Five products are never open together on one bench.
    • Time every treatment on the same watch to the same contact time, and count the scrubs aloud so somebody else can hear the count.
    • Rinse each patch with the same jugful from the same tap and hang every treated patch to dry in the same place for the same hours.
    • Trace each dried patch again on fresh tracing paper and count the squares the remaining stain covers, giving a measured area beside the human score.
    • Have three people score every patch against the drawn wall scale, knowing it only by the random letter a second person gave it, with the key kept out of the room, and write all three scores separately rather than agreeing one.
    Write down: The five treatments with their timings and scrub counts, the three blind scores per patch, the mean score, the spread between the repeats of the same method, and the before and after square counts.
    Finished when: Every patch carries three independent scores and a traced outline with a counted area before and after treatment, and no two products were ever open at the same moment.
    Commonest mistake: Scrubbing the stubborn patch a little longer to be fair to it. Those extra scrubs become the reason it won, and the test then measures your arm rather than the method.

  5. Cost each use

    50 minutes
    Work out what one use of each method actually costs in rupees.
    • Measure each product before and after its test with the kitchen scale, the jug or a counted number of drops or level spoons, and record the quantity consumed.
    • Divide the pack price by the pack quantity longhand in the margin, leaving the working visible, to get rupees per millilitre or per gram.
    • Multiply by the dose used to get rupees per use, then add the water as one line marked as an estimate with the reason beside it. There is no fuel line: nothing is heated in this test, so fuel is zero by protocol, and costing it would inflate every rupees-per-use figure on the page.
    • Draw the result on squared paper: rupees per use up the side, mean score along the bottom, one labelled point per method, with the scale stated.
    • Underline the cheapest method that scored four or five, and underline twice the most expensive method that scored two or below.
    Write down: Rupees per use for all five methods, the dose behind each figure, the counted areas, and the drawn cost-against-score chart.
    Finished when: You can name the cheapest method that scored well and the expensive one that did not, and show the longhand arithmetic behind both.
    Commonest mistake: Costing by pack price instead of by dose. A large expensive bottle can be the cheapest per use, and only the quantity consumed tells you which.

  6. Name the cost

    50 minutes
    Finish the costed problem statement and choose the method the household will switch to.
    • Write four lines: whose problem this is, how often the stain happens, what the current method costs per use and per year at that frequency, and what the winner would cost instead.
    • Multiply rupees per use by the stain count from the fourteen-day log longhand, scale it to a year, and write the difference as one rupee figure. Write the caveat in the same line: this assumes your fourteen days are a typical fortnight, and they may not be — a week of oily cooking, a festival or somebody away from home moves the stain count more than the product does.
    • Pin the patches themselves in a row across the page, grouped by method, with the cost figure written under each group and the number of patches per method printed beside the ranking. If each method got one patch only, print that limit in the same size as the ranking before you name a winner.
    • Choose the winner on cost and score together and write: 'The household will use X for a fortnight, and I expect rupees per week to fall from A to B and minutes per week from C to D.'
    • Read the page aloud to whoever does the washing and have them sign and date it if they agree to the switch.
    Write down: The one-page costed problem statement, the yearly figures for the current method and the winner, and the switch written as one testable sentence.
    Finished when: Somebody who was not there reads the page once and repeats your rupees-per-use figures back correctly.
    Commonest mistake: Picking the top score whatever it costs or however long it takes. A method nobody will keep using for a fortnight measures nothing at all.

  7. Agree the switch

    40 minutes
    Write the rules that keep the switched fortnight's measurement identical to the baseline fortnight's.
    • Write what stays fixed: same log columns, same drawn scale, same watch, same scorer, same tap, same brush.
    • Write what is allowed to move: only the product used to treat the stain.
    • Set the winning product aside in one container, weigh it or mark its level on day one with a pen line, and write that starting reading down.
    • Rule two blank labelled rows for weeks one and two, with the dates beside them, before any data exists.
    • Write your prediction on the page, date it, and have one person witness it with their signature.
    Write down: The protocol as a numbered list, the two week dates, the starting weight or marked level, and the witnessed dated prediction.
    Finished when: The page holds empty labelled rows waiting for two weeks and a signed prediction that predates the data.
    Commonest mistake: Starting the switched fortnight with a fresh bottle and no starting mark. Mark the level on day one, or the fortnight's real cost can never be recovered.

  8. Week one switched

    20 minutes across the week — a few minutes on each day a stain happens, written the same day
    Run the household on the winning method for one week and log every stain event the day it happens.
    • Log each event on the day: item, product, quantity used, minutes spent scrubbing, and the score against the drawn scale.
    • Read the container level or weight at the end of the week and compare it against the sum of the logged doses.
    • Trace one treated item's stain before and after, so the switched fortnight carries a measured record beside the patch tracings.
    • Write down what went wrong: a forgotten entry, somebody reaching for the old bottle, a stain treated twice, an event nobody told you about.
    Write down: The week one rows complete — events, rupees, minutes, scores — the container reading, plus a dated failure entry.
    Finished when: Week one carries every column the baseline fortnight had, and the failure log holds at least one honest entry.
    Commonest mistake: Reconstructing the whole week from memory on Sunday. Entries written days later lose the minutes, and minutes are half the finding.

  9. Week two and the comparison

    45 minutes, plus a few minutes on each day a stain happens across week two
    Finish the switched fortnight, normalise both periods and compare them honestly.
    • Keep logging every stain event through week two, changing nothing the protocol does not allow.
    • Divide each fortnight by its two weeks, longhand, to get rupees per week and minutes per week for both periods.
    • Draw two separate charts on squared paper, each to a stated scale, because rupees and minutes are different units and never share an axis: two bars for rupees per week, before and after, on one, and two bars for minutes per week, before and after, on the other.
    • List every confounder you can name: fewer stains this fortnight, a cook away from home, a price change, warmer water, somebody scrubbing harder than before.
    • Write the change as a rupee figure, as a percentage and in minutes. Say how many stain events the percentage rests on: with ten events it can only move in steps of ten points, so claim no change smaller than one step. Then say plainly whether a fortnight on each side is enough to be sure.
    Write down: The two drawn comparison charts, the per-week figures for both periods, the difference in rupees and minutes, and the confounder list.
    Finished when: You can state the before figure, the after figure, and at least two reasons the difference might not be your doing.
    Commonest mistake: Comparing the two periods as raw totals. Divide both to rupees per week and minutes per week, or a fortnight that lost a few days to travel or illness will look like a saving you made.

  10. Share and reflect

    60 minutes
    Publish the finding, defend it to real people, and record what the household will keep.
    • Deliver the defence live: ten to twelve minutes of unseen questions answered out loud in front of two witnesses who sign and date the page. There is no recording on this route.
    • Read the one-page explainer to three people who wash clothes in this house or nearby and write down what each of them said. If that means leaving the house, a named adult goes with you and stays within sight.
    • Ask your teacher to send the cost-against-score chart from the school address to the expert with one question: what would you have controlled that I did not.
    • Ask the household in front of a witness whether the switch stays and why, and write the answer down word for word.
    • Complete the relations ledger with ten codes, roles, dates and what each person replied, keeping the sheet that matches codes to names with your school.
    Write down: The defence, signed and dated by its two witnesses, the one-page explainer, and the relations ledger holding ten coded relationships.
    Finished when: Ten coded relationships are logged with dates and replies, and the household has said on record whether the switch stays.
    Commonest mistake: Calling it a success because the house smells better. The metric is rupees per week and minutes per week — report those first and opinions second.

What the student hands in

Nine pieces. Together they are the folder a parent can sit down and read.

1. Question cardOne card naming the stain, the cloth, the five methods already in the house, and the question: which one shifts this stain best, and what does each cost per use.
2. Expert interview packFive written questions for a dry cleaner, housekeeping supervisor or formulation chemist, your cost-against-score chart attached, the date and channel of the request your teacher sent from the school address, and the reply recorded word for word. If no reply came, the questions as sent, the dated attempts and one named published source stand in its place.
3. Evidence logEvery dose measured, every contact time and scrub count, the random letter each patch carried and the key the second person held, all three blind scores per patch, every pack price with its pack quantity, and every stain event logged on the day it happened.
4. Failure logThe patch scrubbed longer than the protocol allowed, the entry written three days late, the week somebody used the old bottle, and what each one did to the comparison, all dated.
5. The buildThe test set-up itself — one bowl rinsed and emptied between methods, one brush, one timer, the fixed photograph rig or the drawn scale — with the patches in a row and the cost-against-score chart.
6. One-page explainerOne page a neighbour reads in ninety seconds: the stain, the five methods, the rupees per use beside each score, the switch, the switched fortnight's result, and what this cannot tell them.
7. Identity cardA name and a one-line promise for the winning method, so the household can refer to it by name, plus the single sentence you want repeated in somebody else's kitchen.
8. Relations ledgerTen coded entries, each with a role, a date and what was said: E1 the cleaning professional or chemist, A1 to A3 the people affected who wash clothes here, P1 to P3 the peers who checked your controls, and R1 to R3 those who answered when the chart was sent. No names appear in the ledger, and no health, money or literacy detail about anybody. The sheet matching codes to names is held by the school and destroyed after moderation.
9. The defenceTen to twelve minutes of unseen questions, answered live in front of two witnesses who sign and date the page: the stain, the controls held still, the scores, the rupees per use, the switched fortnight, and the limits you accept without argument. A recording is optional evidence and never the requirement; on the No-Tech route there is no recording at all.

The expert they have to find

Ten logged relationships are required before this project can be marked. One of them is an expert, and this is who.

A dry cleaner or laundry owner, a hotel or hospital housekeeping supervisor, a formulation chemist at a soap or detergent maker, or a quality-control chemist who tests cleaning products for a living.

How to find one

Name institutions and roles, not individuals. The institutions are dry cleaners and commercial laundries, the housekeeping department of a hotel or a hospital, the quality laboratory of a soap or detergent maker, and the chemistry department of a nearby college or university. The roles that can answer are the stain technician at the counter, the housekeeping supervisor, the quality-control chemist and the formulation chemist. You do not make the approach yourself. You write the five questions and hand them to your teacher, who contacts the institution from a school address, names the school, and arranges either a written reply or a call with the teacher present.

What to say

Dear [name or role], I teach at [school]. One of my learners has tested [number] household cleaning methods on identical stained patches, holding the water, the contact time and the scrubbing constant, and has costed each one per use. Could you spare fifteen minutes — on a call with me present, or by written reply, whichever suits you? Their five questions are below.

What to ask

  • When you test whether a treatment works, what do you hold constant, and which of those has caught you out before?
  • How do you decide a stain is gone — by eye, against a scale, or by something you actually measure?
  • What do you pay per use for the product you reach for most, and how do you know that figure?
  • Which household remedy do customers believe in that you have watched fail on your own bench?
  • If a stain like mine arrived at your counter, what would you do first, and why that first?

If no reply comes, submit the questions exactly as your teacher sent them, the dated record of the attempts, and one named published source in the expert's place. That route scores: the gate is a properly made approach, never a reply somebody was pressed into giving.

The defence

Eight of the twenty marks. A student who cannot answer these has not finished, however good the artefact is.

  • Would the household's cleaning spend have fallen anyway this fortnight without your switch, and how do you know?
  • Three people scored your patches by eye, working from random letters given by somebody else who kept the key. What would two more scorers have done to your ranking, and what could still have told them which patch was which?
  • Show me how many patches each method got. If it was three, show me the spread between them and say whether it is smaller than the gaps in your ranking. If it was one, show me where that limit is printed beside the ranking and tell me what a second run would most likely have changed.
  • A neighbour has harder water and a different cloth. Which part of your result travels to their house, and which part stays in yours?

How far a student can take it

starterYou run five methods on identical patches, one method at a time, score them against a scale written beforehand, cost each per use from the pack price, and question one professional who cleans for a living.
practitionerYou choose the stain and defend the choice, cite the pack price and pack quantity behind every cost figure, and make one chart of cost against score that a stranger reads correctly unaided.
researcherYou write the protocol before the first patch, justify three blind scorers and the dose you chose, and quantify the error added by your eye, your water and the number of runs you managed per method.
contributorYou set your ranking against a published cleaning or surfactant study, printing your own measured scores beside the published figures rather than in place of them, defend your controls to a chemist who disagrees, and publish your raw scores, doses and patch photographs through your school, where your school agrees they may be published.

If you want to go further

Run the same five methods against a second stain and find out whether the winner holds or whether the ranking turns over completely.

When it goes wrong

  • If nobody replies to your interview requests - then ask your teacher to try the next institution on the school's contact list, accept a written reply if that is what suits them, and if nothing comes back submit the questions as they were sent, the dated attempts and one named published source instead.
  • If the household or the site says no - then run the whole method on school property with a member of staff, log the school's own stain events across the same two fortnights, and hand it in as the same folder, marked the same way.
  • If your before and after look the same - then report that as the finding, check first whether the household actually used the winning method on every stain event, and write what you find in the failure log.
  • If you cannot weigh the product used - then count level quarter-teaspoons or drops from the same dropper, weigh one dose once on a shop's scale, write that conversion at the top of the page, and mark the row as estimated.
  • If you run out of time - then shorten the switched fortnight to one week rather than dropping the baseline fortnight, normalise both to rupees per week and minutes per week, and print the shortened period on the charts themselves.

Before you start

Safety and consent.
  • Never mix cleaning products with each other. Bleach with an acid — vinegar, lemon, lime, a descaler or a toilet cleaner — or bleach with ammonia releases a gas that damages lungs. This rule is absolute: one product per bowl, each bowl rinsed and emptied before the next, and no leftovers poured together. Only one product is open at any moment — it is closed and put back on the shelf before the next one is opened, and five products are never out together on one bench.
  • Air that moves is a requirement, not a preference: an open window, an open door, or an outdoor tap, and the test does not start without one. Gloves and eye protection are worn for every test. One named adult is in the room from the first bottle being opened to the last one being put away, and they stay for the whole session. Nothing is heated, boiled or put near a flame; every test uses water straight from the tap.
  • If you smell fumes, or anything stings your eyes, skin or throat - stop, leave the room, tell the adult, and rinse the place it touched under cool running water for several minutes. Do not go back in to tidy up. Then tell the adult who knows where you are, the same day, tell your teacher before the next session, and write what happened in the failure log.
  • Nothing is tasted, nothing is deliberately smelled, nothing is inhaled to identify it. Keep every product in its own labelled container, never decant into a drinks bottle, and rinse skin or eyes under running water immediately on contact.
  • Any product carrying a hazard symbol is used exactly as its label instructs, or it is left out of the test. If the label is missing, or you cannot read what is inside, it does not go near a patch.

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