Some weeks ago my electric kettle ceased to be . I've since been using a hob kettle. Now when I make the tea, the tea goes frothy. Why is this? Is it just because the water boils hotter on the stove? It doesn't do it every single time which seems strange.
If I turn the electric kettle off before it's fully boiled (so as not to 'scald' the coffee) there is always a 'scurf' on top. But of it fully boils, there isn't - could it be the same for your hob one?
You must have something in the kettle that reacts with the water. Was it a new one ? Did you bring it into a soft water area from previous use in a hard water one ? Not sure about the "not every time" though. That's a puzzle. Maybe it was a different brand tea :-)
It's quite an old kettle. Kept it on standby for when we have power cuts.
It does still have the original descaler thingy in it. Could that be it, lol! It's stopped working.
If you shake the cup so the froth turns into mini-waves and add this tea diffuser you could have a good sing along... :o)
http://oi58.tinypic.com/2hwl2li.jpg
The temperature at which water boils is dependent upon atmospheric pressure which in turn is dependent upon elevation above sea-level. Perhaps there is a difference in height between cupid's stove top and counter top:)
Not to get too technical, cupid; however, if the kettle does have a thermostat that cuts off the heating process, then the water hasn't actually boiled: It's just been heated to a high temperature.