Check out Rocktumbler.com. They recommend 2 Tbsp per pound of material for nearly every recipe! I usually only burnish for an hour. Do you think it makes a big difference to do it much longer? I dont generally have unused grit left over in the Nat Geo 3 Lb tumblers. I use 4 Tbsp in the 3 lb Lortone tumblers (per manufacturer instructions) and it happens in those barrels ocassionally. They don't actually hold 3 lbs of material - more like half of that. Sort of misleading on their part.
Gotcha! I know the Nat Geos are considered toys by some but I have to say, I have 6 of the 3 Lb professional models and they hold 2.5 lbs and the results are better than the more expensive (and critically reviewed) Lortones for results. They have day/speed timers, nice rubber barrels, run pretty quietly and produce nice tumbled rocks. From my experience, not toys and pretty nice, workhorse tumblers that produce some lovely batches of tumbled gems.
They also stand behind their product. I had two with engine issues and they replaced them at no cost with no explanation required if they failed within a year.
Check out Rocktumbler.com. They recommend 2 Tbsp per pound of material for nearly every recipe! I usually only burnish for an hour. Do you think it makes a big difference to do it much longer? I dont generally have unused grit left over in the Nat Geo 3 Lb tumblers. I use 4 Tbsp in the 3 lb Lortone tumblers (per manufacturer instructions) and it happens in those barrels ocassionally. They don't actually hold 3 lbs of material - more like half of that. Sort of misleading on their part.