Measuring the composition of some tin-based alloys (in the original form of solder pastes)
First I melt the solder, pour off the flux and then tip the molten metal into a little round mould to give a little slug like this.
Then- to make it nice and flat and expose a fresh surface- I machine it with a lathe (it's a soft alloy so very easy to machine and the swarf doesn't give you splinters!)
Then I pop the sample face down on the spark stand of this atomic emission spectrometer (spark AES) and give it a whack with the electrode (it goes bzzzzzzzzzzzzzzzzzzzzzzzzzzzz-zzzzzzzzzzzzzzzzzzzzzzz-zzzzzzzzzzzzzzzzzzzz)- some magic happens and it displays the composition of the alloy (selected elements I'm interested in, anyway- silver, lead, bismuth, nickel, antimony, copper- several others)
Meant to have been a 15 minute job but the bismuth composition was low so a recalibration, preparation of new samples, re-testing of a known-good sample followed- took up a lot of time. Still not resolved so will pick it up again next week.