Size and shape, strangely, are the things that most people find difficult. Because we're so used to the idea that a bath is something that is longer than it is wide, most people seem to assume that all baths must be like that for a standard bathroom, and don't give the matter much more thought. The fact is that baths can be bought in such a huge array of shapes and sizes that there's probably one that's perfect for every bathroom in the country.

If, for example, you have a small or a very square bathroom, you might find that a corner bath, either square or rounded, is right for you. Although corner baths tend to be a bit less popular with really tall members of the family, they can be great for bathing kids. They use space efficient, and can be fitted with showers just like any other bath. On the other hand, if you're more interested in style than utility you might consider an oval bath, or some other shape that breaks up the boring straight lines that seem to typify the design of most bathrooms.

Colour is another tricky issue. The exact colours available to you will depend on the material from which your new bath is made - for more information about materials, see below. Basically if you buy an acrylic bath you have a much wider choice of colours than if you buy an iron or steel bath. Metal baths are enamelled, and there is a relatively limited number of coloured enamels on the market. With an acrylic bath the colour goes right through the material of the bath, so any scratches and scuffs won't show up a different colour underneath. Obviously this is not the case with enamelled metal baths - deeply scratched enamel will reveal the metal underneath. However, it can be repaired relatively easily, and the probability of your damaging your enamel that badly is really quite small.

The reasons for choosing one particular material over another for your bath are quite subtle. As we've said, there are basically two choices: an acrylic bath or a metal one, made out of either cast iron or rolled steel. From a purely practical point of view, you should consider acrylic if the bath needs to be carried up tight or weak stairs to get to your bathroom, or if you're not confident about the strength of the joists beneath your bathroom floor. The average bathroom floor in the average house is quite strong enough to support a cast iron bath full of water, but if you know of or suspect some sort of structural weakness you should either get it sorted out or opt for acrylic. Don't forget that an acrylic bath full of water still weighs a lot, so for complete peace of mind you should consider asking a builder's advice before installing a bath in a room that has never contained one before.

If you're not constrained by practicalities, it really comes down to taste. A metal bath - unless it's free standing in the centre of the room - looks much like an acrylic one to a casual glance. But some people would say that an enamelled metal bath gives a bathroom a certain sense of class that an acrylic one does not. It looks and feels in some way substantial. Another strong argument in favour of metal is that it pretty much constrains you to go for a timeless look - an exotically coloured acrylic bath might look pretty cool now, but it might look pretty awful in ten years. By re-enamelling, you can also change the colour of a metal bath - something that's impossible for acrylic.

Metal baths are also very, very tough. Although the enamel might suffer a little, they can take all sorts of heavy usage and mistreatment, and they're unlikely to be damaged by spilled cleaning chemicals or hair dyes. If properly looked after and properly treated to prevent rusting, there's no reason why a metal bath shouldn't take the punishment of generations of users - they potentially have hundreds of years of life.

Acrylic baths, although still pretty tough, are a little more fragile. They will also certainly need a metal frame to support them (usually provided with the bath, and concealed behind the bath panel). After a lot of years of use they may become brittle or begin to deform. On the upside, they are cheaper in the first place, and, because of the ease with which acrylic can be moulded, they are typically available in a much wider variety of shapes than metal baths.