Steel baths better for retaining heat

Am getting a bath in, what would be the best type of bath ? , are steel baths better than plastic for keeping water warmer? ay other points I have missed would be appreciated.

Metal baths retain heat better but are much heavier - so are your floors fit for it.

If a bath is quite deep, the heat retention is less of an issue. I've a deep, claw foot plastic bath and it stays plenty warm to watch an hour long programme in comfort in the bath.

Exactly the opposite is true. Metal has a much higher specific heat capacity than plastic. It is also much more thermally conductive. So when you put hot water in a metal bath its heat is not only very quickly shared between the water and the bath (resulting in a lower average temperature), but it is conducted to the outside surface of the bath where it is radiated away. The metal is warmer to the touch, which may give the illusion that it is "retaining the heat", but in actuality the reverse is the case.

dub_nerd said:

Exactly the opposite is true. Metal has a much higher specific heat capacity than plastic. It is also much more thermally conductive. So when you put hot water in a metal bath its heat is not only very quickly shared between the water and the bath (resulting in a lower average temperature), but it is conducted to the outside surface of the bath where it is radiated away. The metal is warmer to the touch, which may give the illusion that it is "retaining the heat", but in actuality the reverse is the case.

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+1
It would be akin to having a large radiator in your bathroom.

Thanks for the replies Lads

This makes sense , just wondering if there are any advantages to having a steel bath?

I went to buy a steel bath (not cast) to put below a shower hoping to stop movement.
The owner of the plumbing company said he only sold them to hotels. The reason being that they could not be burnt by people smoking in the bathroom.
I would advise against them

Go raibh maith agat Dinny

Had a bathroom done up two years ago and have had to replace the bath already due to cracking. Make sure you don't get the skimpiest plastic bath ... 5 - 8 mm thickness is a must, especially if it is used for standing under a shower.

Thanks DubNerd, will get thicker bath

dub_nerd said:

Exactly the opposite is true. Metal has a much higher specific heat capacity than plastic. It is also much more thermally conductive. So when you put hot water in a metal bath its heat is not only very quickly shared between the water and the bath (resulting in a lower average temperature), but it is conducted to the outside surface of the bath where it is radiated away. The metal is warmer to the touch, which may give the illusion that it is "retaining the heat", but in actuality the reverse is the case.

Click to expand...

Well, actually, this is partly true. According to wikipedia, steel has a lower specific heat capacity (0.46 J/gK) than say polyethylene (2.3 J/gK). This means it takes five times more energy to increase the temperature of a given mass of polyethylene than steel by one degree Kelvin. This is not really that important though.

Much more relevant is the thermal conductivity. Steel (16-24 W/mK) is much more thermally conductive than polyethylene (0.42-0.51 W/mK). Steel and metals in general are much better at conducting heat away from the bathwater and therefore may feel warmer to the touch as pointed out, but this is energy being taken from the water.

In summary, if you want to keep the bath water warm for longer, go with a plastic bath, or think about insulating the underside of a metal one.

With a metal bath, you could run some very hot water into it and let metal absorb the heat, then add more water to required temperature and water level. We have a metal bath and it was simple job to change colour from its original orange to white with 'Renubath'. I dont think you can do with plastic baths. On a bathroom makeover, the plumber said it would be a big job to get the old bath out and it would have to be broken up. So I came up with idea to change colour and am happy with result.

I have a heavy metal bath and I feel the room/floor temperature dictates how quickly your bath retains or loses heat. My feeling is plastic baths are less prone to this. Personally, I prefer metal baths for both the look and durability. Mine is very old and I had it resurfaced by Renu-bath some years back and it was as good as new.