BetterBags

Shopping bags are not-very-strong, this because they are cheap, disposable and (now) biodegradeable. Like most not-very-strong things they break if you overload them, usually when you've put too many expensive glass bottles in one bag. We've all done it, walking through the car park when two bottles of chardonnay and a bottle of McGuigan Black Label escape out of the bottom of the bag and onto the tarmac in thousands of pieces.

If plastic could be manufactured (and I'm fairly certain it can) to discolour under stress, it should be a simple matter to manufacture plastic bags that change colour as they are approaching their weight limit. Because they are manufactured entirely from this material, they will start to discolour wherever the fault appears. For example, if you were to (stupidly) put in a bottle of wine upside-down, you would be well within the designed weight limit of the bag and the handles would be in no danger, but around the top of the bottle there will be a lot of pressure on the plastic. This would turn, let's say, red, alerting you that the bag was about to give way at this point and maybe you should double-bag. Or turn the bottle the right way up.

Happier shopping makes happier shoppers.