I built my reflux still a few years ago. Used it several times, but the output always seemed to taste a little funny. Last time I used it, I took the tower off to clean the pot and set the tower on a white towel. A few hours later I noticed that the tower had leaked whatever condensation it had in it onto the tower and it was a pure looking blue!
As I was moving, I took the whole still apart, thinking I would clean everything and rebuild it. Recently I push the copper scrubbers out and they were horribly corroded. Then it occurred to me that copper does oxidizes to a greenish corrossion, (like pennies do.) I have been using a sugar wash, stainless steel pot witha cork gasket - everything else is copper.
How can you ever expect to get a pure liquid when using a copper tower and scrubbers? Or am I doing something wrong.