Andrew McKay wrote:

Hey Andy, welcome back...

not seen you in these parts for a while!


--
Cheers,

John.

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Weatherlawyer wrote:

I believe it is called the "hot chocolate effect":
http://www.sas.org/E-Bulletin/2004-0...ack/index.html

Interesting... that would seem to support both my viscosity change /
damping effect and Guy's air bubble / velocity one.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
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Might I suggest this item?

http://cgi.ebay.co.uk/very-old-brass...QQcmdZViewItem

Or this:

http://cgi.ebay.co.uk/FINE-OLD-PLATE...QQcmdZViewItem

On Sat, 09 Dec 2006 16:02:02 +0000, in uk.d-i-y John Rumm
wrote:

Roger R wrote:

Now, using the bottled water it doesn't make any noise at all until just off
boiling, but even then its much less than before. I can hear the radio
again. So I think the noise is made much worse by hardness in the water,
making a very thin - invisible micro scale layer on the element, but why
that should be make the noise worse...? Something to do with the breakdown
of the temporary hardness of the water during boiling perhaps.

It may be that the scale adds roughness to the surface which acts as a
seed site making it eaiser for cavitation to occur....

Our kettle has been equally noisy from new, so I don't think lime scale
buildup is an issue, though the presence, or not, of dissolved lime may
well be. I'll give bottled water a try if I can bring myself to buy
some