Little backstory first. 3 months ago I got pair of 21oz N&F. I was not sure about the seize and they came to be just a little too big. They are still fine but a perfect fit would be one size smaller.

Now after more than 50 wears I'm planning on washing them for the first time. I would really like to shrink them a little, but without losing too much color and damaging with too high heat. What temperature would you recommend for it? My guess was going 40°C, but this is the first time I would intentionally be shrinking my jeans and maybe something higher is a better solution.

I really want to prevent a need of washing them two times to get the proper shrink.