Even if you shell out a small fortune getting the perfect creamy colour at the hairdressers, just a few short weeks later, your hair can often turn an undesired shade as your icy tone fades fast.

Fortunately, there are several things you can do to both prevent and fix an attack of the brassy blondes. Here's what the experts have to say...

Why does bleached hair turn brassy?

When your hair is lightened at the hairdressers, it's usually bleached with a mixture of ammonia and peroxide. Even the most silvery of bottle blondes are left with some underlying pigment in the hair though, and as the artificial colour begins to fade, the warm tones start creeping back in.

"People assume that if they leave bleach on their hair for long enough, it will go completely white, but there's still some natural pigment that's left inside of the cortex which never goes away," explains Michael Shaun Corby, global creative director of Living Proof . This is why brassiness tends to strike in dark hair that gets dyed platinum or blonde.

"Some people also have what I call a 'pre-existing condition' though, which is when they previously had their hair tinted a darker shade for the winter, or added some highlights between. This causes permanent staining that never goes completely light.

"As hairdressers, we tone those away with pearl tones, violet tones and shades of blue and red. But when the blue molecules fade, you're left with a sort of 'stained plastic look' that's brassy, yellow and orange."

Tip 1: Shampoo the hair only once

Lather, rinse, repeat. It's a mantra that many of us follow in the shower, but all that double cleansing could be stripping your hair of its precious colour - and with no real benefit to its cleanliness.

"Keeping the beautiful work that your stylist created as long as possible starts with shampooing less," says Corby.

"I always advise shampooing only once, not twice, because you don't need it."

Tip 2: Dry hair immediately out of the shower

You might think that leaving your locks to naturally air dry is the best way to keep your blonde in top condition, but experts say this is the first mistake many people make after leaving the salon.

"The longer the hair is wet, the more the [blue] molecule is prone to fall out of the hair," explains Corby.

"Rather than waiting, get your hair dry straight out of the shower using a hairdryer, and spray in lots of heat protection."

Tip 3: Skip the straighteners

It's tempting to recreate those perfect loose curls you left the salon with, but if you want your blonde to go further, it's a good idea to limit your use of heated tools, like tongs and straighteners.

"Excess heat to the hair can cause blondes to go brassy, especially if your colourist uses a toner," explains Katie Hale, head of colour at Charles Worthington.

"The more heat used, the more it effects the cuticle," says Hale, "which strips out any toner or anti-brass shampoos that have been used on the hair."

Tip 4: Go for a colour refresh

"Pop in to see your colourist for a 'colour refresh'," says Hale. "This usually involves applying a glaze to remove any brassy tones and amp up cooler ashy tones."

Hair toner can help you correct or personalise your colour, to control brassiness and keep hair looking healthy.

The blonde toners used by hairdressers usually come in a purple colour, since the violet reduces yellow tones and eliminates brassiness. A silver shampoo or home toner can help to keep your colour in peak condition between appointments too.

Tip 5: Change your shampoo game

"Use a clarifying shampoo, such as the A'kin Moisture Rich Wheat Protein Shampoo on the hair once a week," advises Hale. These shampoos remove the build-up of pollution or product (like dry shampoo) that coats the hair and makes it look murky or dull.

Drying sulphates are chemicals used as foaming agents to form a lather in many shampoos, but they can strip your hair of their natural oils, so look out for sulphate-free options, which are kind to colour-treated locks.

As a general rule, most experts recommend washing your hair every two to three days, and although opinion is divided on the matter, the overwhelming majority say washing too much can cause hair breakage.

"Wait for three days before you shampoo, and maybe even make it four, if you can stretch it out," says Corby.

Tip 6: Dry shampoo is your best friend

Corby's biggest tip? "Invest in a good dry shampoo, one that doesn't make your hair feel texturised or dirty."

A decent dry shampoo will remove all the excess oil, sweat and odour that's built up in the strands, leaving you with fresh, clean hair that will last for many days.

"Spray it in and leave it for 30 seconds," is Corby's go-to technique.

"People spray, rub and then spray again, but that's the wrong way to use it. You want to spray, wait for 30 seconds and then brush it out."