A small steady stream as the copper got up to ~1800F
It's apparent your pyrometer is not correct, for copper melts @ 1981° F. You may find literature that claims a slightly higher melting point (just a few degrees). Unless you're melting an alloy, you're achieving a much higher temperature than you assume.
The ingots came out black with an reddish-brown tinge. After hitting one with the brass wheel, it quickly cleans up as a bright copper bar.
A little trick that will help with surface appearance is to dump the solidified ingot in to cold water while it's still red hot. That will remove the vast majority of oxide coating. I used to do that with the ones I cast. A fast and easy way to clean them.
The surface is irregular where it cooled quickly against the form though, ended up layered and separated like sheets of paper in a couple places.
If you're troubled by that, coat your mold with mold dressing (or soot from an acetylene torch), then preheat the mold somewhat. That should eliminate the cold shuts you're achieving. Super heating the copper a little will help, too, but if you're using an electric furnace, you're already running it near it's top end I would think.