I have a question about ferric chloride for etching. How long will a 1:4 solution of Ferric last. I’m thinking of trying to do a hamon once I’ve refined my finishes. If it’ll only last a year or so, I may buy a second bottle as a backup. It its good and stable for years I may just get one bottle. I suspect its more related to number of blades or prevention of contamination but I’d like to hear what you guys think. Btw, I saw a great video from Ed Caffrey on etching this week.