Hello Daughter in Distress ...

Hello Daughter in Distress - In answer to your Question:

What can you use to get the stuff off the bottom of the kettle?

You can use vinegar or citric acid with water to remove scale from inside a kettle
- see this video on how to:

http://www.videojug.com/film/how-to-descale-a-kettle

[there are other cleaning tips attached to the clip - taps - sinks ... the list is endless !

OR you can buy commercial De-scaler from most supermarkets or a hardware store.
and follow the instructions on the packet.

* Make sure the commercial de-scaler states for use on kettles.

Good Luck,

Jill