The Detergent Question

What is the best type of detergent to clean cloth nappies?

After many weeks of discussion and consultation with several soap, fabric and water experts, this is the experimental protocol the working group produced:

Updates to the protocol are in green. These are changes we made as we went along, which happened when experimenters had questions we hadn’t thought about in the planning stage.

1. Recruit at least 15 volunteers to test each detergent. 35 volunteers were recruited. 
2. Send each volunteer 3 random samples of detergent from the list below including instructions on how to measure the right amount (based on water type and drum size) and guidelines on how to run the experiment. Each sample of detergent will be labelled with letters A, B or C. 105 detergent samples were sent out, however due to dropouts only 81 were returned.
3. Each volunteer will clean their machine by doing three empty washes with no detergent before each test to remove traces of old detergent in the machine. Then each volunteer will run 4 washes of their normal dirty nappies, using detergent A, B or C plus a control test (water only). The choice of detergent for each wash will be random and blind to the volunteer (it will be performed and annotated by a partner, friend, relative etc, as to be unknown to the volunteer. We will supply each volunteer with an empty eco egg shell which will also be put into the machine by the confederate, so that the bumping noise doesn’t give away the eco egg test).  Due to a mistake with how the experiment packs were packaged, participants knew whether they have an Ecoegg to test, so participants left out the shell altogether. In practice blind testing  using a helper was not possible for everyone, though it was done where possible.
4. The wash routine will be the same for all: cold pre rinse, 40ºC wash, additional rinse. If regular washes needed to be done between the experiment washes, an empty rinse cycle was to be run prior to each subsequent test wash. Test nappies had at least one wash in the participant’s usual washing agent between the trials of different washing agents. It did matter if the test nappy is weed or pooed in.
5. Each volunteer will be asked to select a certain material to swab (i.e. cotton, bamboo, microfibre). A guide on how to swab will be provided. A set date will be given for the volunteers to conduct their tests, so that all the swabs can be returned at the same time. For example, the A test will take place one week, then followed by the B the next. The samples should be posted first class back to the labs, because each sample needs to be sent immediately.  The part of the nappy closest to baby’s bum was swabbed (excluding liners). For pocket nappies, participants swabed both the microfleece and the absorbent material (with the same swab). Not all participants were able to send back the swabs on the same date, so they were sent back in weekly batches. 
6. Once washed and dried, each volunteer will assess the cleanliness of the nappy based on subjective measures and using a descriptive scale to record softness, smell and look.
7. Each volunteer will also fill out a survey with the following information: water hardness, washing machine type, washing machine age, nappy material washed and drying method used.
8. We will finally gather all the results and compare how well each detergent performed relative to each other.

The detergents that have been chosen for the experiment are:
Sainsbury’s non-bio powder
Sainsbury’s bio powder
Sainsbury’s non-bio liquid Sainsbury’s non-bio liquid tablets were used in the end as liquids are very difficult to send in the post.
Totsbots Potion
Sainsbury’s non-bio powder + Miofresh sanitiser.