Norman, when we carry out the thermite the vast majority of the product is not magnetic despite what looks to be some nice balls of iron (we do it over water so it forms balls). Our understanding is that our mix is not perfect and consequently the iron formed is contaminated with so much iron oxide, aluminium powder and various unreacted ignition materials that you can`t detect the magnatism from the produced steel. I could be miles away from the truth, but it seems very possible. It also rings true since the balls crumble easily, so they are clearly not pure iron - that said, some lumps are magnetic so it is working to a degree....and besides, it looks good!
I`d love to see a video of them actually using the thermite reaction practically. We have to teach that it is used to "repair railways lines" but have no video showing it and in all honesty, no proof that this actually is done other than me being told to say so!
good luck and stay safe....
Chris