You’re welcome Joy, This is a latent subject it seems; and many have crawled out of the woodwork, well…they’ve come forward and granted expert opinion about this historical technology which obviously predates the wheel [and fire]. It would appear, like cooking and burping baby, much information has come down the pike via word-of-mouth from mother to daughter passed down over the millenia — less so from father to son — in fact, they’re disgusted, [I believe!]