Heat shrink tubing is an expanded plastic product which contracts when it is heated. The contracted tubing can be used to seal connections, identify cables and much more.

There are different kinds of heat shrink tubing. The tubes are available in different materials and different sizes, they also have different shrink ratios. The principles of application remain the same for every piece of tubing.

When you have the correct equipment, applying heat shrink tubing is relatively easy. The ease of use is one of the reasons why heat shrink tubing is such a popular material for protection, insulation, decoration and more.

But making sure you get the perfect connection and a smooth clean seal every time is more difficult.

Getting a perfect seal is about having a simple and easy to follow process which you can put into place easily.

Follow these three steps to perfect heat shrink application.

Step one – Choosing the right size heat shrink

To ensure that your heat shrink fits snugly on your substrate, you need to do some basic but important measurements.

You need to pay attention to a tube’s recovered diameter (diameter of the heat shrink after heating) and the expanded diameter (before heating). Ensure that the recovered diameter is slightly smaller than the area you are going to apply the heat shrink to.

You also need to check that the expanded diameter is wide enough for you to maneuverer the tubing into position prior to heating. If, for example, you are applying the heat shrink to the power cable of an iron, you need to make sure the expanded diameter is wide enough to pass over the plug.

Step two – Cutting the heat shrink to size

Once you are happy with your vertical measurements, you can move onto the horizontal. Measure the area that you want to cover with heat shrink ensuring that there will be a slight overlap on each side.

Remember that as well as shrinking in diameter, heat shrink tubing also shrinks longitudinally as well. A piece of heat shrink will typically only shrink by about 5-7% but it is important to bear in mind before you go snipping the heat shrink with scissors.

Heat shrink can be tricky to remove if you do it wrong, so make sure you measure up properly before you do any heating.

Step three – Position and heat

Work the heat shrink into the correct position, making sure it covers the required area. If you are covering a splice joint, then ensure that the heat shrink tubing is right in the centre and has the same amount of overlap on each side.

Once you are happy with the placement of your heat shrink tubing you can begin heating. First, check the shrink temperature of your tubing. This should be available under the manufacturer's specifications.

Set your heat gun to this temperature and heat up the heat shrink by gently moving the heat gun back and forth over the tube. For a more even application, you can hold the heat shrink tubing in place using zip ties.

We don’t recommend using a lighter or blow torch because this uneven heat can damage the tube and cause uneven shrinkage. It's also important that you don’t set the heat gun on too higher heat. This can cause the heat shrink to go brittle and snap easily.