I surprised myself in that the balls soldered securely, first time round, but I let my attention wander for half a second and the edge of one of my discs buckled. Still. I'd intended to LoS the earrings, so I made the warped one into a stick / tie pin* with some 1.2mm sterling wire and a push cover and the other into a pendant. 

I also took my eye off the ball when filing, and nearly filed through my finger. The moral of this is that if you have some alligator tape, you should jolly well use it!

A really enjoyable project, and one that I'll repeat in the attempt to get a matching pair. Thanks Jo.

*After doing all the photography, I realised the pin looks a little warped. It isn't - I hadn't realised the inherent problem with using wonky slate to put it on, but happy to take one for the team ;-)