Clean carbon takes a Washer Chamber to make which requires sealant glue to make which requires a mixer to make which requires clean carbon to make.

Only things craftable are the Purification Chamber, Still Chamber, and Copper Boiler. Everything else requires either Clean carbon or sealant glue to make, which take each other to craft.

Is this a bug, or am I just missing something completely obvious?

Wait I figured it out, vanilla bug, you can use pure carbon for it, vanilla only looks at one of the recipes for autocrafting the entire machine and doesn't consider other recipes.

Ok :)