When it comes to shrinking heat shrink tubing, nothing beats a heat gun. But if you do not have one, what should you do?
Rest assured, you can still use heat shrink without a heat gun. It responds to many sources of heat, so there are plenty of alternative tools that you can use instead.
In this article I have listed some of the most popular alternate methods for shrinking heat shrink. I have no doubt that you already have some of these tools lying around!
What temperature does heat shrink tubing need?
Whenever you choose a tool for heating shrink tubing, it is important to keep the tube’s shrinking temperature in mind. For the most popular tubing materials, Polyolefin and PVC, these lie around 90°C (194°F) and 100°C (212°F), respectively.
If you don’t sufficiently heat the tubing, it does not shrink to its full potential. This leads to a loose fit that does not protect well.
Aside from the shrinking temperature, each type of heat shrink also has a maximum temperature. This is not as important when choosing a heat source, as it is always possible to reduce heat by moving the heat source further away.
Alternatives to a heat gun
A hair dryer (or blow dryer) can sometimes be used instead of a heat gun. Blow dryers are just small heat guns, after all.
Whether you can use a hair dryer for heat shrink depends on the specific model of hair dryer and the type of heat shrink being used. Hair dryers tend to have a low upper temperature limit for safety reasons, and not all of them get hot enough to activate shrink tubing.
Depending on the output temperature of the blow dryer, you might get full, partial or no shrinkage. Polyolefin heat shrink is likely to work best, as it has the lowest activation temperature of common heat shrink materials.
To use a hair dryer on heat shrink, simply set it to its highest heat setting and hold its nozzle close to the tubing until it shrinks. You will have to rotate the wire or blow dryer to evenly spread the heat.
Be patient as you wait for the tubing to get up to temperature and shrink. Because of the low temperature, it can take a while with a hair dryer.
An alternative option for activating heat shrink is a simple lighter. It has a sufficiently high temperature for every type of heat shrink and works quicker than a hair dryer. But it does come with some limitations.
One thing to be careful with is that its open flame can leave black soot on your heat shrink. This is not an issue if you use black tubing, but for colored tubing this can be something to watch out for.
You can mitigate this problem by holding the blue base of the flame next to the heat shrink, instead of the tip.
Another possible issue is the effect of the flame on other objects. If held too closely, it can burn heat shrink, wires, your fingers and potentially ignite flammable materials in the area.
If you have no other solution available, and you are working in a sufficiently safe area, a lighter is an okay option for activating heat shrink. But even then, it is still tedious.
One step up from a lighter is a butane torch. Not only does it give you a flame that is easier to control, it also outputs more heat to a larger area. For multiple or larger pieces of heat shrink, this tool is a much better solution.
While higher temperatures sound riskier for overheating shrink tubing, in practice there is not that much to worry about. Reducing the flame and/or holding the butane torch at a greater distance from the tubing is enough to prevent damage.
You can also use a soldering iron to activate heat shrink. This method works best on small pieces of tubing. For shrinking larger pieces, the limited surface area and heat of a soldering iron is not enough.
To use a soldering iron for heat shrink, hold the barrel of the iron close to the tubing without touching it. Move the iron back and forth while rotating the wire, so that heat can reach all sides.
When using this method, make sure to not touch the heat shrink with the tip of the iron. It is way too hot and will burn, melt or warp the tubing.
Hot air rework station
One of my favorite ways to activate heat shrink is with a hot air rework station. It lets me precisely control the air temperature and I already have one on my workbench for soldering purposes.
A simple hot air rework station, like the 858D model, is more than sufficient. If you regularly deal with soldering and other electronics work, a tool like this provides you with a lot of utility outside of activating shrink tubing.
For heat shrink, you would use it like a standard heat gun. Set the heat to the appropriate temperature for your heat shrink and move the nozzle around the tubing until it has evenly shrunk. That’s all there is to it.
Things to watch out for
When shrinking heat shrink (with or without a heat gun), there are a couple of things you must keep an eye on.
- Make sure to use the correct size of heat shrink. If you use tubing that is too large, it will never shrink to the right dimensions. For this reason, I always recommend having a kit with a variety of sizes of heat shrink at hand.
Here you can find instructions for calculating the correct heat shrink size.
- Check the tubing’s specifications before you start. Not all heat shrink is the same, knowing the maximum temperature and shrink ratio of your tubing is essential in getting good results. You can typically find this data on the sales or specifications page of the particular heat shrink, or imprinted on the tubing’s side.
- Avoid overheating. When heating heat shrink tubing with something other than a heat gun, there can be a risk of overheating the tubing. Overheating can cause the shrink tube to become brittle or damaged, so try to avoid this.
So why even use a heat gun?
With so many alternatives out there, why would you even use a heat gun? Surely, shrink tubing does not know the difference between heat from a hot air gun, lighter, hair dryer or soldering iron, right?
To get reliable results with shrink tubing, it is important to heat it with a controlled heat source that is not too hot, not too cold, does not light anything on fire and that does not make a mess of things by leaving soot or other residues behind.
The easiest way of achieving all this is to use a heat gun. None of the other methods above give the same results. While they do meet some of those criteria, using them can also lead to uneven shrinkage, improper insulation or even physical damage from overheating.
For things like adhesive-lined heat shrink, a hot air gun is the only option to evenly shrink the tubing, heat the glue and form a proper waterproof seal.
Which hot air gun is best for heat shrink?
The good news is, heat guns for heat shrink are very affordable. There is no need for a fancy model with high temperatures, temperature regulation or fancy attachments. A simple hot air gun for heat shrink can be picked up for about $10-15.
Hair dryers, soldering irons, lighters and butane torches are all valid options for activating heat shrink tubing. They rarely give perfect results and are tedious to use, but they are better than nothing.
Pay close attention to overheating, as this can cause heat shrink to degrade and become brittle. Picking the right size of heat shrink is important too. If you choose a diameter that is too big for your wires, it will never shrink to the right size.
A heat gun always gives the best results with heat shrink. You can pick one up for about $10-15 and save yourself quite a bit of time and annoyance.