painting on copper

prepping copper for oil painting:
- Use fine grit sandpaper or wool to create a "tooth".
- Rub crushed onion juice on the copper an letting it dry (this seems to take forever)
- To create a strong bond, apply a thin layer of resin or mastic varnish

Begin your painting with 3 layers of a lead white ground letting them dry between layers. This is kind of like laying down your first layer on the slippery panel and then coming back the next day to continue.