Alloying sterling silver?

Hi!
I've just tried [unsuccessfully] to alloy some sterling silver for the first
time. Seems like it should be easy right?
Melted 31.1g of fine silver with 2.5g of 99.95 pure copper (I analyzed it at
work). Both metals were cleaned in acid then washed off in water first.
I'm using a propane / O2 torch and stirred the heck out of the molten metal
with a quartz rod..... Poured it into some water to make some grains and
lo-and-behold....
I got a mess!
The copper and silver separate into a un-homogenous clump. I tried several
times to get it to blend but it's being very stubborn.
Any help on the topic would be much appreciated.

Thanks!

Dave B.