Why Do Freezers Frost Up?

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By Elizabeth Masterman

Reading Time: 4 minutes

With the invention of frost-free freezers, you may have thought that frost in your freezer was a thing of the past. If your supposedly frost-free freezer has developed a layer of frost, you may wonder if your appliance has a problem. So, what causes frost build-up in a freezer?

What Causes a Freezer to Frost Up?

Every time you open your freezer door, the warm air from outside meets the cold air within, creating condensation, which then freezes, forming a thin layer of frost. Over a period of time, these layers can build up. This is perfectly normal.

How Do You Know When Ice Build-up is a problem?

If the ice has got so thick that it’s taking up space in the freezer, or it’s stopping the door from shutting, then you need to take action. Another warning sign would be if you notice the amount of ice has increased suddenly.

If you think there might be a problem with your freezer, there are a few simple things to check.

Was the Door Left Open?

Firstly, might the door have been left slightly ajar? If warm air has been continuously entering your freezer, this will contribute to a thicker layer of ice.

Signs to look for include condensation on the outside of the freezer, and perhaps a tiny puddle of water underneath the freezer door, where the frost has started to melt.

If you think the door may have been left open, check the food carefully, because if anything has started to defrost it will need using, rather than allowing it to freeze again.

You should also check the door seals, also known as the gasket. If the seals are damaged or dirty, they can allow a small amount of air to constantly seep into the freezer.

You can check if the seals are working efficiently by placing a piece of paper on the seal, closing the door, and then trying to remove the paper. If you can remove the paper without opening the door, there is a problem with the seals.

If this is the case, clean the seals with a toothbrush, using a mixture of 1 part bicarbonate of soda and 3 parts water. Rinse and dry the seals thoroughly. Then check the full length of the seals to see if there is any damage. If the seals are damaged, they need to be replaced.

How Do You Avoid Frost Build-up?

Try to open the door as infrequently as possible, and when you do, keep the door open for as short a time as you can. You can make this easier by organising your freezer carefully so that things are easier to find without rummaging about in it.

If you freeze freshly cooked food, give it sufficient time to cool down before putting it in the freezer. If hot food is still steaming, then this steam will create condensation which then freezes and turns to ice.

You also need to make sure food is either wrapped securely or placed in properly sealed containers, as otherwise, moisture can escape from the food and then freeze, adding to your ice problem.

Freezer Containers

You should also avoid overfilling your freezer. It’s best to keep your freezer around 70-80% full to achieve optimum efficiency.

Having frozen food in the freezer helps keep it cold, but if there is too much in there it means there isn’t enough space for the air to circulate, which will stop the freezer from working efficiently.

How Do You Remove Frost Build-up?

The best way to defrost a freezer is to unplug it and leave it with the door open, allowing it to defrost in its own time. It’s a good idea to use up as much food from the freezer as you can beforehand.

When you are ready to defrost your freezer, remove any remaining food and store it in the fridge or in cool boxes with ice packs.

Be aware, this won’t stop the food from defrosting, it will simply slow down the process, so if the ice is particularly thick and you think it’s going to take a while to defrost, it’s worth asking a friend or neighbour if they have any space in their freezer.

Next, switch off your freezer at the wall and unplug it, making sure the plug is kept off the floor and out of the way. Put towels in front of and inside the freezer to absorb the water as the ice defrosts. Then leave the door propped open and simply wait for the ice to melt.

Once the ice has melted, wipe away any water, give your freezer a clean with a cloth and antibacterial spray, then you can plug it back in and wait for it to get back down to temperature.

Can You Leave Frost in a Freezer?

If space is at a premium in your freezer, then it can be really frustrating if chunks of ice are taking up valuable space. Ice can also stop the door from closing properly, allowing more warm air to creep in, intensifying the problem.

If left for too long, it can also cause an unpleasant, stale smell within the freezer.

Frost Build Up in a Freezer

Perhaps more significantly, if you leave frost to build up for too long, it means your freezer has to work harder, using more energy and making it more expensive to run. It also puts extra strain on the working parts, reducing the life of the freezer.

If ice is building up particularly quickly, this can be a sign that something is wrong with your freezer, so defrosting it regularly can make it easier for you to notice when something’s not right.

Don’t worry, we’ve put together our full guide to defrosting freezers here.

Do you still have questions about freezers frosting up? Then check these common questions out:

How Often Should You Defrost a Freezer?

As a good rule of thumb, you should aim to defrost your freezer twice a year, or when the ice is around 6mm thick.

Is Ice Build Up in a Freezer Bag?

A thin layer of frost is perfectly normal. However, every time you open your freezer door, this thin layer is joined by another thin layer, and over time this can create a thick layer of ice, which can be much harder to remove.

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