Giving something a "deep clean" is a somewhat trendy thing to do these days for reasons unknown, but if it's good enough for hospitals and kebab shops then it's good enough for Hopcraft towers and our stock of casks!
For the past 3 years we've followed the cask washing mantra of...
1) steam clean cask with 130 degree steam from the Karcher
2) visual eye / nose inspection of cask
3) if it passes, then it's taken inside for filling (rinsed with peracetic first)
4) if it fails, then it's washed again, tested again, and if it still fails the residue / rancid aroma test then the cask will be filled with caustic solution and left to sit for a few days before being emptied, rinsed and inspected again....
Before being filled with beer the casks are peracetic rinsed to sterilise them and flushed with CO2 to hopefully evict as much oxygen as possible to prevent staling in cask.
Now, however, we've added an additional step after the cask is brought inside for filling of giving every cask, if possible, a kegbrite wash followed by a water rinse. Kegbrite is a chemical which is designed to remove hop residue and other baked on crap from inside casks - and if you've looked inside as many as I have you'll know how much potential for crap there is inside casks - which can only, hopefully, improve our final product's stability and shelf-life further.
So, the policy of "permanent revolution" rumbles on, pushing it's nose into all aspects of the brewing process, and I for one welcome it.... and so should our customers with better beer leaving the brewery!