I have a bottle of concentrated formaldehyde based Tetenal STAB (stabilizer, 1:100 mixture ratio for creating stabilizer solutiion for E6/C41) that I have been using over the last year for slides. There is no printed expiration on it, but I believe it may have been made in 2010. Does anyone (PE?) know if formaldehyde based stabilizer lasts for a very long time? Or is it prone to oxidize or break down over time once opened?
Thanks in advance.