DIY Dehumidifier

Why Does The Windscreen Mist Over?

Do you have problems with the windscreen fogging up on the inside? It’s there because water vapour in the air has condensed on the cold windscreen.

How Does The Water Get In The Car?

There is almost always water vapour in the air, you can’t do much about that. The natural water vapour stops you getting sore throats and coughs. Other water can be introduced through wet clothing, your breath and leaks that let rain water into the car.

If you have a Roadster and it mists up badly, check under the carpets for the inevitable pond. The water gets under the carpet and sits there until the car is driven and the heater is put on (or the car is left out in the sun). The heat turns the liquid water into water vapour and this ends up on the windscreen. (Or in worst case scenarios, on the printed circuit board of your SAM unit, causing it to die).

Clearing the windscreen is very easy and has already been previously covered here.

How About Making It Not Mist Up In The First Place?

Makes a lot more sense doesn’t it. The problem is cost and space.

You can buy dehumidifier products which either come in small plastic buckets or cloth bags. The problem is that the buckets take up space, cost a lot and aren’t reusable. The cloth bags are usually quite expensive and can be large but can be reused.

Making Your Own For Cheap

You knew that was coming didn’t you?

1 litre dehumidifier buckets and cloth bags are about £10(ish) However, it’s very easy to make a 4 litre dehumidifier for as little as £2. These home made dehumidifiers can be easily reused. What you need is some socks. If you have odd socks, that’s perfect. Ideally cotton.

To fill them, you’ll need cat litter.

Not any old litter though. You need to get the crystals. This bag is 4 litres and cost me about £4.

Crystal cat litter is silica. The same as the small sachets you find in boxes of electronics.

It’s a dry crystalline product that soaks up water from the air and holds it. We just need to get the crystals into a porous and hard wearing case. In this instance, a sock. Grab a funnel or cut the top off a plastic bottle.

Hold the sock over the end and start filling up the sock.

When it’s nice and full, tie up the end securely.

To tidy the end…

…you can open it out…

…and fold it back over the end of the sock. Yes it looks like a big black penis.

You have one made.

Repeat with other odd socks or socks you really hate. You’ll need 3 or 4 socks to use all 4 litres of silica cat litter.

The filled socks are easily hidden around the car. At this point, I recommend weighing them for future information.

Silica Gel – The Facts

It’s not a gel and it doesn’t feel wet even after absorbing the full amount of water. Silica crystals are a desiccant which means it will pull moisture from the air. Silica crystals are best at dehumidifying enclosed spaces like boxes and car interiors. It is non toxic despite what the little packets have written on them. Silica crystals can absorb 40% of their total weight.

Reusing The Magic Water Socks

When the silica inside the socks has reached their maximum absorption, they need a refresh. You can put them on a hot radiator for a very long time but it’s less than ideal.

The best thing to do is to put them in the oven at 100 to 120 degrees Celsius. An electric oven is preferable and cotton socks are less likely to melt.

The duration required is hard to calculate due to the thickness. Flattening them a bit will help.

The reason for weighing them will now become apparent because when they are wet, they will be heavier. Keep them in the oven until they get down close to their original weight. They are now dry again. They can now be redeployed back into the car.