I recently took afairly big, old transformer apart by boiling it (on a low simmer) in ordinary drain cleaner (sodium hydroxide). I cooked it for several hours, turned the heat off and left it on the stove until the next day. The liquid solution we buy in Denmark holds 40 % weight/volume and that should probably be diluted to about a quater to half that strength. I used the solid stuff and added that to some water in the pot.
WARNING: People who are chemists (I am) can skip this paragraph. Others should know a few things about this chemical before working with it: 1) Always wear safety goggles! (This stuff is nastier than battery acid in terms of burns. It is also much harder to rinse off as it turns the fat in your skin into soap and it penetrates much deeper). Rubber gloves and a plastic apron are prudent measures, too. Your prime concern is not to get the stuff in your eyes or face. 2) It evolves much heat when poured into water. Don't add too much too fast or it may boil violently and spray drops on you. Add the concentrated drain cleaner into the water. Never do the opposite - the heat can get out of hand. Your prime concern is not to get it in your eyes or face. 3) Do NOT use an aluminum pot. Drain cleaner, especially when hot, attacks aluminum ferociously. The pot will dissolve and the reaktion evolves hydrogen (explosive gas). You can safely use most other metals. And glass lids are also safe to use. Steel or stainless steel and glass is left unharmed, though very clean. 4) Sodium hydroxide is not poisonous. It burns, so don't drink it, of course. But, once the pot is rinsed it will be perfectly safe to use for food afterwards. Small dilute traces of it will not harm you in any way. 5) It does not emit any harmful vapours or gasses (if you keep it away from aluminum). If you smell anything, it is just the laquer getting broken down.
(Back to the subject): The laquer dissolved completely on the outsides of the transformer and softeded to a slime, gel or gum on the inside of the coils, dependig on how well it had permeated.. The laminations were really easy to pry loose with a stanleyknife afterward. Only the first layer needed a bit of chiseling with a hammer and screwdriver because of the physical tightness. I was even able to salvage most of the magnet wire in a reusable condition. Apparently the insulation laquer on the wire was indifferent to the drain cleaner. (I wouldn't bet on it, though. So I'm not going to use it for anything high voltage). The whole dissasembly operation was performed in the kitchen sink under gently running water to prevent caustic burns on my fingers.
