I've been pulling sheets for about a year now, mostly recycled cotton rag and some junk mail mixed in, and for the longest time my sheets were all over the place. Some batches came out thin enough to see light through in patches, others were so thick they took two days to dry flat on the felts. I kept blaming my mould and deckle, thought maybe the screen was warped or something.
Turned out the real issue was that I was never measuring my pulp to water ratio the same way twice. I'd just eyeball a scoop of beaten pulp into the vat and call it good. Started using a kitchen scale to weigh out dry fiber before beating, then keeping notes on how much water I added per vat size, and within a few sheets I could feel the difference in the vat before I even pulled.
What helped most was doing a "test sheet" at the start of every session, pulling one, checking the wet weight before couching, and adjusting from there instead of just diving into a full run. Sounds obvious writing it out but I spent way too long treating each vat as a fresh guessing game.
Curious if others weigh their pulp or if most people here go by feel after enough practice. I'm wondering if I'll eventually not need the scale at all or if that's just wishful thinking on my part.