How a Cold Heat Soldering Iron Works

Joints and Irons: Soldering 101

A traditional soldering iron
A traditional soldering iron
Photo courtesy Consumer Guide Products

One of the best ways to understand how a Cold Heat tool works is to examine how it's different from a traditional soldering iron. Electrical soldering irons usually have a resistance heating unit, similar to what you would find in a hair dryer or a toaster. Electrical current passes through the heating unit, and electrical resistance causes the unit to get hot.

It takes time for the heating unit to make the bit hot enough to use. It can also take a while for the bit to cool off again. This is partly because of the nature of heat itself. Heat is essentially a change in energy within an object. The heating unit warms the bit by passing energy into it. In the process, the bit's molecules begin to move faster and faster. As the bit cools off, it transfers heat into the air around it, and its molecules slow down again.

The amount of time required for the bit to cool off is also related to its emissivity. Emissivity is a measure of how efficiently a substance can transfer heat into its surroundings. The materials used in soldering-iron bits, such as copper, chrome and nickel, have a relatively low emissivity. In other words, they're not very efficient at releasing warmth into the air around them and cooling themselves off in the process.

A Cold Heat tool is different. Instead of plugging it in, waiting for it to heat up and waiting for it to cool off again, you just turn it on, touch the solder and go. To a casual observer, this is the incredible thing about Cold Heat.

But tools that do the same thing have been around for quite a while. They're called resistance soldering tools, and you can even get plans for making your own online. A resistance tool uses two probes that can look like rods, pliers or tweezers. These probes pass a current through the solder. The probes and the solder heat up very quickly because of their resistance to the current passing through them. Removing the solder breaks the circuit, and the tips cool off quickly.

The Cold Heat tool might look like magic -- some prominent explanations for how it works even feature magic -- but electrical resistance should get all the credit. The tool uses the same principles as a resistance soldering tool, but in a significantly less expensive package. We'll look at this in more detail next.