I find its alot quicker to just cover the bottom of a sauce pan with it and put it on the stove on high. When the "eruptions" settle down shake the pan a bit to move it around then let it cool.
When its "erupting" it almost looks like its boiling.
The sodium carbonate powder is not as fine of a powder as sodium bicarbonate, its a bit grainier. You can see the difference.
I have had it in a mason jar for probably a year or so and it hasn't re-hydrated, so I don't think its a big issue.
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