Lo all, and happy new year!

I wonder if anyone can advise on a soldering mishap I had. I had two commissions for collars (they ordered on the 9th in time for valentines day, then the wire I use was out of stock until end of last week, so I've been a bit ) and whilst the first one went well, I had problems fitting the staple for the fastening into the holes to rivet it. I did eventually manage it though. After, I filed the back down to solder a small silver plate over the rivets. I applied the heat and it was looking good until I turned the collar over and saw the solder had flooded through to the front. It actually looked quite good because it made smooth joins between staple and collar, but I need to get it off to be hallmarked tomorrow and I'm worried about the amount of solder on there and also about the colour difference. I've filed it down loads and then I put some more heat on it and there is clearly loads more solder on there.

So, what i would like to know is, how do I know when I'm filing the solder off when I've hit silver, or is there a better way of doing it?

cheers, in desperation, Liz