Berg Copper toning experiment with my Night Clings image that I sent for my postcard.
I thought about copper toning them all but wasn't sure if it would appeal to everyone so I sent them out untoned. I like the reddish image, it lightens it back up a fair bit and loses the sky detail.
The copper seems to need a print 1-2 stops darker than normal while selenium needs about a stop or so lighter than normal. Depends on how long you tone too of course.