bms wrote:other type with RN (Orca) coating
I'm pretty sure Ocra isn't RN - otherwise it would be called RN. I think this is a chinese/ thai copy of the RN coating.
I've noticed 8" plates come Orca-coated these days. The coating is dishwasher-safe. Plates never were dishwasher safe but a few batches ago, a batch came with Orca labels on them. I had someone put one through a dishwasher for a number of runs and it came out fine. The old ones barely stood up to hand-washing. They're much better to print with than the old ones were as well.
Whether it's a "chinese copy" or whatever, I couldn't say, but Revolution do state that their mugs are coated in the UK.
If, as you say, Orca is different to RN and I get the pits with RN mugs but not Orca, it suggests the problem is in the coating (or how it's applied) and it's solved by using a different coating (or one that's applied by a different manufacturer).
Either way, I'm throwing away less mugs with the Revolution ones due to white spots. Obviously I'd prefer to go back to RN coated mugs from my previous suppliers but I'm not in this business just to top up the landfill.