Optimal electromagnet bobbin material

[jlknauff]

I can't seem to find any answers on this...I'm experimenting with some electromagnet designs, but I'm not sure what the best bobbin, or end caps would be. I was thinking about using steel washers welded to the iron core since it would be the strongest, but I thought that may affect the EM field. The other option was to use nylon washers attached to the iron core using a special industrial epoxy because it would have no effect on the EM field.

Any thoughts on this?

 

[Xiao10]

Wouldn't a steel washer remain magnetised after the current is switched off?