Does regular descaling damage a kettle and make it more susceptible to limescale?

[Peter]

Does anyone have any comments on whether regular descaling of a kettle causes surface damage that can make it more susceptible to limescale in the future?

[Rolyata]

We use one of those knitted wire thimble things in the kettle.

So long as you wash it out every couple of months, it totally solves the scale problem.

Our kettle is about ten years old and the inside is perfectly clean, but previous kettles have been badly furred up within just a few months use.

[s--p--o--n--i--x]

Use filtered water.

[Dave Liquorice]

Your water isn't particulary hard if it takes a few months to become baddly furred, either that or you don't use the kettle that much. B-)

In a real hardwater area a kettle becomes badly furred in a few weeks. Our rapid boil kettel would start to trip on the safety cut out if it wasn't descaled every 5 weeks or so. The water Co changed the source of our water about a year ago, from a local adit to a reservior in the next vally. Haven't descaled the kettle since and there is virtually no scale in there, pity about the brown stain, presumably from peat.

The knitted metal ball things do help with only mildly hard water and are easier to clean, just scruch up under running water. But with really hard water I doubt that it would make much difference.

[David Lang]

Properly formulated kettle de scaler will be 'buffered' to reduce it's effect on anything other than limescale. Ordinary acids not specifically intended for this purpose may also attack other items.

Dave

[Mr Fizzion]

Filtering water cannot remove dissolved ionic salts.

Mr F

[john49]

Oddly enough, it is more likely that _using_ it has that effect. For the scale to form the minerals (normally calcium/magnesium carbonate plus a touch of silica) need a nucleation site to begin to form their crystals on. once a seed crystal is formed, it will continue to grow as long as there is available saturated solution. I have not got my reference book to hand, but I think all three minerals have a positive solubility coefficient i.e. they are more soluble in hot water than cold. If the kettle cools with boiled water in it further crystallisation will take place This is how Travertine marble (really a limestone) is formed by hot springs. The buff squiggly stone on the front of a certain very litigious burger chain is this rock. But I digress.

When you boil water it cavitates i.e. a bubble forms and collapses. The collapse is violent, so violent in fact that it can damage metal. Eventually the bottom of the kettle will be microtextured, with myriad nucleation points. If the cavitation is bad enough, it can, over time, erode metal. If you try to put too much shear stress on water cavitation occurs. I once the impeller of a Francis turbine (hydrelectric use, water powers the turbine) which had been in service for 20 years. A quite staggering amount of bronze (15%?) had been removed. Cavitation also affects ships propellers, which keeps bronde foundries in business. If the propeller is run grossly too fast the cavitation can get to the stage where almost the entire propeller is a cloud of cavitated water and the efficiency is greatly reduced.

Finally, should you wish to see nucleation points in action, buy yourself a pint of fizzy cider or lager. When it was settled examine the liquid near the side of the glass. Do you see a stream of little bubbles heading to the surface? They are all coming fron the same point. That is a nucleation point.

John Schmitt

[Andrew Gabriel]

Well, all the 'filter' jugs contain ion-exchange softeners as well as filters, so they do in practice exchange out the salts which cause hard water.

[dave stanton]

Nice chemistry/physics post John

To the point

Dave

[David Lang]

If you go to

there is a little box where you can enter your postcode and it tells you how hard the water is!

Dave

[Rob Summers]

Only, I'm afraid it doesn't seem to be very accurate..... erring on the side of "Please buy more Calgon" even for postcodes that I know don't have hard water.

Rob

[Mike Dodd]

Mine, it claimed was a medium level area, and recommended Calgon for every wash to avoid damaging the washing machine.

Hmmm

9 year old kettle - no scale

Washing machine packed up after 6 years - entirely due to a slipped belt, which snagged the wiring loom and in repairing it, I knackered the level sensor; New washing machine = 3 years and going strong.

Pinch of Salt?

[Dave Liquorice]

I got " Soft Sorry, we do not recommend using Calgon for soft water areas." Sorry? I'm not but I guess they are... I'd have expected medium if they had data for the old supply not the new.

I did notice that the full entered post code changed to just district level (the first half) when I clicked submit. Bunging in the same full postcode but without the central space gets " Not Available. We're sorry! There are no records for your location, if in doubt use Calgon in every wash."

So it looks like they are doing it on district sized areas and the page coding can't cope with a postcode without the space. The area is to large and the page coding hasn't been properly tested.