I opened my kiln this morning after my glaze firing yesterday and found some pieces melted...they didn't explode, they didn't warp or bubble, they actually melted. I'm so confused why this would happen. I fired to cone 6 in my electric kiln and what's also curious is that other cups I slipcast with the same slip, and positioned next to a piece that melted, are intact and made it through like normal. And one piece that melted was not a slipcast piece...it's so odd. Any thoughts? Has this happened to anyone else?