First real job while in high school was tanning leather at a couple of ancient, now shuttered, firetrap leather tanneries up in Peabody & Salem, Mass. Used to work 2nd shift and tan 'raw' New Zealand sheepskins that came in on pallets. For 6-to-8 hours, a huge quantity of leather would rotate inside of dual wooden tanning-wheels (picture a giant wine cask that holds 10,000 gallons of fluid) constructed of 2" thick bands of Italian wood and lined with dozens of oversize wooden pegs to keep things from clumping up. At various intervals you'd pump in chromium, formic acid, wattle, dyes, etc.. Drain it......fill 'er full of cold water a few times & 'rinse' ....then send thousands of pounds worth of wet leather & water crashing down into the 20 foot-long, 3 ft deep 'carts'.
Funny story for all of you pack rats out there. I saved one piece of tanned suede as a souvenir and had it stashed away in various boxes & drawers for close to 30 years. I can't begin to tell you the number of times over the years that I'd happen upon the stupid thing while cleaning out a box and think about tossing it in the trash. Never did though. About two months ago, I took my jacket in to get dry cleaned and they somehow managed to mangle the leather collar and even tear a small gash in it that couldn't be prepared. I searched the house, found that piece of leather and the nice Thai seamstress who works down there used it to make a replacement collar. Thirty dang years I schlep that silly piece of leather around...and then one day...bing!!