Crystal is mashed in the corn, at home I would consider taking green malt (after sprouting but before drying) and BIAB it, then drain, dry and kiln, temperature and time of kilning is mostly what determines colour.
Stewed malts (Vienna, Munich... Aromatic, Biscuit) are heated up late in the sprouting process to encourage melanoidins, then dried and kilned, hotter kilning for darker versions. In the old floor malting days they would at the end of sprouting, heap up the malt and cover it with tarpaulins so it got hot and high in CO2.
Amber to Black are just malt dried then kilned at higher and higher temperatures. The term Black Patent is because to get true black malt there was a fair chance of the malt catching fire, some one "Patent" a drum roaster that made it a safer and controlled process, there days fires in maltings are pretty rare, mind you Joe White burnt down one of theirs a decade or so ago.
Malt is one of the primary ingredients in brewing, knowing a bit about malt helps us choose the right malt for the job at hand, its also a real craft/science in its own right. Lots to learn and it would be fun to play around with if I had the time.
Big ups tubbsy, hope it works well for you.
Mark
