On Sun, 14 Jan 2007 12:52:24 -0000, Sal wrote:

Is mould in a shower unavoidable,

It's more like mould in silicone sealer is inevitable. The sealer contains
acetate, a by product of the curing process, which is very tasty to mould,
in laboratories moulds are often cultured in an acetate solution.

One solution is to use a more expensive sealant. However these are also not
without their problems. I use "Evostick Nail and Seal" for many jobs. It's
far superior to silicone since it is a sealant designed for use below the
waterline in boats immersed in salt water. It does not support the growth
of mould. Sadly if used where it can be seen, it has the unfortunate
characteristic of yellowing with age.

An alternative is to use a polyurethane sealant such as Sikaflex which is
also resistant to moulds.