Which would make the cost of each mirror higher, right? Additional processing will naturally increase the cost per unit.
By the way, super cool project and thank you for sharing. My experiments with concentrating sun power when I was a child were directly related to the spontaneous combustion of insects. Still making amends for the number of ant hills my brother and I cooked with the sun.
I still naively think that we could make mirrors completely encased in glass to limit their degradation (pure speculation here).