The moral of the story: when doing a big plate AND a filament switch,

The moral of the story: when doing a big plate AND a filament switch, be extra-careful to clean up thoroughly!
http://toybuilderlabs.com/blog/2013/10/7/filament-dust

I just noticed carbonized dust in my clear PLA that I just switched to. Although this could be clear PLA dust as well i guess

I find that just a purge isn’t enough to clean out old colors, I really need to work it back and forth some (retract 1x, extrude 2x, repeat a few times). My working theory is that this pulls molten plastic off the walls inside the nozzle.