[dadkar2]

Yes it sounds like your current is too high. It should definitely not froth. The black stuff is a smut that will form if the current is too high. It should polish off, but you should lower the current. Start by putting a 100 ohm resistor in series with the part. Radio Shack has them. Buy 100, 220, 330, and 470 ohm and try them starting with 100 ohm until you get the color and result you want.

Ken