Elfie suggested that my beloved laundry balls might be a rip-off, no better than washing clothes in plain water. I couldn't let that pass by, so I did a little googling. Straightdope tested a different type of laundry ball than mine, and decided it was a scam. In their tests, the ball performed a little better than just plain water (which they put down to chance). But surprisingly the ball also performed about the same as using branded laundry detergent. Straightdope concluded that the balls are a scam, but so is laundry powder.
I decided to put it to the test. I had two loads of laundry yesterday so I washed one with the laundry ball as usual and one with just plain water. Both loads had the same programme and were washed at 40degrees.
I found that the wash with the laundry balls came out nice and clean as usual. I examined it closely and it looked and smelled clean, just as I expect. However a yellow pair of shorts which Sam had been wearing whilst digging the allotment were pretty muddy. After washing with the laundry ball they were still dingy-looking around the hems. This matches my usual exerience of washing with the balls (and also of washing with detergent) - some really grubby things need a second pass.
To my surprise, the wash with just plain water also came out nice and clean. It looked and smelled just as clean as the laundry ball load. Believe me I examined it carefully, but it seemed absolutely fine. Without having a more accurate way of measuring cleanliness, the best I can say is that I would be happy if every wash came out like that.
It looks like the balls are a waste of money (and perhaps so is laundry powder, as StarightDope suggested). But a friend on the newsgroup uk.rec.sheds suggested that for a true test you'd need to do many washes, as a small amount of left-behind grime could accumlate and the difference might only show up several washes later.
I carried out one last test, the toughest yet. Eleanor fell into a muddy puddle at school and her red tights and cardigan and her white polo shirt all had a thick caking of mud. Based on the experience with the yellow shorts, I knew the washing balls wouldn't get this out first go, and I thought plain water probably wouldn't either. I washed the uniform at 60degrees with a tablespoon of Ecover bleach and half a cup of washing soda. To my delight they came out good as new first time, even the white shirt.
I will continue washing our clothes with just plain water for the next few weeks to see if the grime builds up. I will also be investigating this whole issue further. What is the best way to wash clothes for maximum economy, effectiveness and impact on the environment?