I'm on Day 14 of 40 and have completed several shorter MCs over the past few years.
This cleanse seems to be more productive as I have been releasing a lot of mucus, gas, as well as dark brown sediment/ sludge (sometimes with an awful stench), especially over the past few days.
I think it's partly because I've been steadily increasing my cayenne pepper.
Whatever it is, I think it's great because, to me, it's a sign that the Master-Cleanse is working hard to get rid of my old old old fecal waste, etc.
Btw, I had my first colonuc yesterday morning. The therapist reported that she was seeing a lot of orange/ yellow mucus and gas in my water discharge. This morning, after my SWF, my butt pee was darker and thicker (like very thick black coffee) than before. I think it's because the colonic helped to remove the loosened gunk and allowed the lemonades to get to the still hardened fecal matter even more aggressively.
I don't know when the dark butt pee will stop - I just want to keep cleansing : )
(Sorry if I didn't answer your question but just wanted to let you know that I am having a similar experience)