This method or trick to separate the ferrite core of the transformers from its winding, I got it from the elemental page in the cheat section.
The main problem for separate winding from core, is that the glue is very stuck being the ferrite quite fragile, and if we try to force it we break it.
To avoid this and remove it without difficulty, you just have to put the transformer Boil it in a saucepan of water for 10 to 15 minutes, so that the glue softens and the winding comes out "without difficulty". Although one of the drawbacks of this method is that we make the winding unusable, but hey… we took advantage of something.
We have tested the method and here are some small commented photos of the experiment.
This is ours small transformer, three columns and a main winding and two secondary ones. East transformer I have had it at home for years, I don't know where I got it from and I have no idea of the ranges it transformed or the coils it is made of, so you are the perfect candidate to disarm.