Question: where does the copper come from that ends up on the nickel strip

title: Copper in architecture
text: A shield can be effective against one type of electromagnetic field but not against another . For example , a copper foil or screen RF shield will be minimally effective against power frequency magnetic fields . A power frequency magnetic shield could offer little reduction of radio frequency fields . The same is true for different RF frequencies . A simple large - mesh screen shield can work well for lower frequencies , but can be ineffective for microwaves . Copper