Hot take: Green sand vs. petrobond is no contest for small batch work
I spent two years messing around with green sand on my home foundry stuff here in Tulsa, fighting moisture issues and inconsistent ramming. A buddy loaned me some petrobond for a brass pulley job last Saturday and I got cleaner casts on the first try with zero tempering fuss. Why are guys still swearing by green sand for small scale when petrobond cuts the headache so much?
You said "why are guys still swearing by green sand for small scale" and honestly I think it's just pure stubbornness... I spent three weekends in a row trying to get my green sand right and ended up with a lumpy mess that looked like a failed science project. Petrobond made me feel like I actually knew what I was doing for once.