A second three hour high-heat smelting reduced the contents of both crucibles completely. The copper came out as a single large button. The tin was different. There was one small button (5g) and a three layer "cake" of slag... a light grey very granular layer was the bulk of it. Atop that was a dark grey layer and atop that were little balls of tin, like a froth, embedded in the borax.
In researching the tin, I find that tin forms a significant amount of tin silicate slag, given the chance. Historically quicklime was added to displace the tin from the silicon. I will try that next time. 40% of the mass of the cassiterite in quicklime is the proportion recommended.