Actually, the factory - if they do it - usually do a great job. And if they do it, the knots are totally invisible and you don't need to do anything!

Problem is, for some strange reason, every now and again the factory sends back units without bleached knots. I don't know what it is that makes them decide whether or not to bleach, perhaps some orders don't state it clearly enough.

Buying some bleach is cheap and it's quick to do, so usually I just bleach myself rather than sending it back.

It's funny you should ask this question because for my first 6 or 7 months of wearing, I also didn't understand why people would ever want to bleach knots when the factory did such a good job. But believe me, you will need to learn to bleach knots at some stage Especially if you get a stock.