Industrial lens and mirror making is surely not a purely manual process. The method described is clearly meant for use with minimal infrastructure. The lack of

Industrial lens and mirror making is surely not a purely manual process. The method described is clearly meant for use with minimal infrastructure. The lack of jigging and tooling then is actually a feature in this instance. The substrate requires sufficient hardness and dimensional stability to hold its shape. While glass is certainly not the only material that fits the bill, it's probably the cheapest. High-end (read Industrial) 3D printers can probably -not- get a precise enough substrate, at least as designed right now.