My coloured ice balloons turned out well, but as soon as I saw them glowing in the sunshine I just knew they'd make awesome ice lanterns as well.
There are several ways that you can hollow out an ice balloon for lantern purposes.
The third option was obviously Brendan's favourite, since it involves power tools, but having tried all three options I'm also a fan of door number three. Not only is it by far the fastest and least effort, but the resulting ice lanterns last longer due to thicker and more even walls.
Brendan duly procured an inch and a half spade bit and in short order we had beautiful holes in the lanterns waiting for candles. We thought we'd use tea lights and they did work, but next time we'll try floating candles instead as the heat from the candle tends to melt the ice (putting out the candle!)
Brendan thought it might be fun to try lighting the tea lights with his handy dandy blow torch. Let me state for the record that while this is amusing, it completely melts the tea light, destroys the wick and melts the ice lantern. It does not actually light the lantern. I suggest long matches instead...