"It all starts with cutting and cleaning plates of brass and copper. In this case the critical dimensions were 50x50x0.7mm (That's 2"x 2" of gauge 22 sheets) First they are sanded with four different coarseness of sanding paper and then cleaned with scouring pads. Then they are left to soak in industrial grade alcohol. After this the sheets aren't touched with bare hands, just soldering tweezers."