Magnetic shielding for Iron Tattoo Machines

how i shielded the side arm and rear of a iron frame to protect it from the flux from the coils so it doesnt suffer the effects of hysteresis and become weak with use. first build of the year , iron bulldog shielded color/shader 4mm gap 400g tension runs on 7volts all day . handmade 10 layer 22g double lacquered hi temp copper wired coils .