I run low voltage and get little to no brown sludge. When I was running 12vdc across the cells, the sludge appeared very quickly. I use a palm sander with 80 grit on the plates, then while wearing rubber gloves, I completely clean the plates with isopropyle alcohol and then put the cell stack together. (+-+-+-+-) I then test fire them for about an hour to observe and make any needed changes. I like to use a clear container for testing so I can see what's going on. This seems to work. It has reduced having to flush the installed cells dramatically.
Randohr
02' Jeep; 18mpg Highway w/o HHO
23mpg highway w/ HHO.
Parallel plate water baths, 3vdc, 16A
Efies(x4), MAP diode, AIT mod, WTS mod.