So today, I'm taking apart a duvet cover I made my daughter last year for her dorm room, which is no longer useful apparently. We have decided a) down comforters are too hot in the summer, and b) we're tired of our shoulders getting cold because the duvet slid down to the bottom of the cover, regardless of how many ties we try to use to keep it in place. Hence, a TON of serging to rip out.
Over the years, I have come up with a method for un-serging that at least works, and is less messy and frustrating than my earlier attempts. I will say that I only have a 4-thread serger, so I am not certain if this method also applies to 5-thread sergers. Here is the only article I found on the subject. So, I will share what works for me. (If you have a better way, I would love for you to share. Please leave me a comment.)
Serging, at least 4-thread serging, consists of 2 loop stitches and 2 straight stitches formed by the needles and held together by the loops. There is no one thread you can pull to make the serged stitch come apart (believe me, I've tried!) So here is the best way I know to un-serge a seam.
First, cut one line of loops. Try to cut only the loops on the side facing you, and not cut any of the loops on the back side of your seam or at the top, where the two loop threads join. Cut every stitch.
Voila! One serged seam, un-serged.