Here it goes:
Most denim, especially prewashed (pre-faded) denim comes "sanforized". In other words. prior to being sewn together, the factories subject the denim to a compressing, stretching process so that it shrinks as much as possible before its turned into a pair of jeans.
That way, you can buy your jeans at whatever size you think you are and not worry about them shrinking dramatically (sanforized denim shrinks only about 1-3%).
Now, even some dry denims are sanforized (eg. nudies, apc etc.).
In the case of japanese denim, it comes "raw", or un-sanforized, meaning, when you wash them, they will shrink up to 10%. Kinda like a shrink to fit kinda deal.
Which is why I bought these true to size 30"; when I got them pre-soak, the waistline was actually 32"...post soak it is now 30" as the tag reads.
And there ya have it...go to wikipedia and search for sanforization.
How to soak them? Usually a 1-2 hour hot tub soak is good. Then let all excess water fall off for 30 min and throw into the dryer along with two dark towels for 30 mins on high heat. Thats what I did atleast.
And I too am scared at the suprising lack of indigo loss...
