>Anyway, I'm using a 3-litre (IIRC) polypropylene cereal container
>as an etch tank. There's a bubbler Araldited into the bottom and
>an aquarium heater fitted to one side. I had loads of trouble with
>"Combi Heater" branded heaters breaking - three DOA, 100% failure
>rate. I've got a Visi-Therm now, which seems to be OK. It's only 25W
>though; in hindsight I should probably have bought something a bit bigger.

I would be tempted to glue or tape some slabs of polystyrene sheet, anything
up to an inch thick, to the outside of the cereal container to stop heat
loss. If you want to see how the etch is going a 2 or 3 inch window in one
slab of the polystyrene would probably be sufficient without compromising
the thermal insulation to any noticeable extent.

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