I can’t be any more clear about the subject of this post than what I’ve selected as the title: this post is a review, it’s about a tool, and … well, it’s not a happy story. I don’t intend on doing this sort of thing here very often, as that’s not what this site is about, but when I get this angry I really want to vent. I’ve been duped, by slick advertising and a full-scale marketing blitz involving several participating companies (including Coleman, Radio Shack, and others), into buying a cheap gimmick that can’t hope to live up to the claims of its manufacturer.

I was shopping for a few items at Home Depot today, to do some work on my Integra as well as the Ohmbre, and while there the thought occurred to me that I really need a new portable soldering iron. I have an ISO-TIP Solder Pro 120 butane-powered iron that has been just wonderful until very recently when it stopped working. A soldering iron like this is based on a simple butane torch, which burns the butane after mixing it with the correct quantity of outside air. This allows the butane to burn at a much higher temperature than the lazy yellow flame that is formed by a simple cigarette lighter. For some reason, the mixing passages became clogged, most likely (my guess) due to collecting too much rosin vapor from soldering in close confines — the fumes got pulled in and collected over time. What little gunk I could pull out was very sticky and organic in nature, which supports the rosin theory.

So, having failed to clean my old iron even with some fairly nasty solvents, I decided to take the $20 plunge and pick up one of these ColdHeat battery-powered soldering tools that I’d heard so much about. I’d seen them being sold at ThinkGeek after all, and to my knowledge the stuff they carry is usually genuinely good, honestly represented and “geek approved.” What geek could resist?

A well-informed one, it turns out. I bought this tool completely on a lark, without reading reviews or doing any sort of real research. I mean, it’s a soldering iron, right? How could you screw that up? Well, had I read the reviews at Amazon, I’d have known better; more on that in a moment. First though, a description of what this thing is.

Calling it a soldering iron is actually incorrect. It’s more accurate to call it a soldering tool, because the term “iron” in this sense implies an object that becomes hot, and is then used to heat other things (solder, a cotton dress shirt, a cow’s hair and skin, political dissidents) via thermal conduction, for some purpose. The ColdHeat tool does not fit this description. Its tip becomes hot, not as a functional part of its operation but as a side effect.

The ColdHeat advertising makes a big deal about the design of its “Split Tip”, but doesn’t really come out and tell you what it does. It’s split, because it’s really a pair of electrodes separated by an insulator. Touch them to a part you want to solder, and the tool pumps an enormous amount of current through the part, and the part’s own resistance causes heating.

In a way, this is some pretty clever outside-the-box thinking. It means that the tool itself requires no resistive heating element of its own, and it means the heating can be localized to the part itself. Why heat up a large metal tip and keep it hot, when all you really want to heat is the part, and the solder? In terms of energy efficiency, it’s a great idea.

There’s just one obstacle, and the ColdHeat’s solution to the problem is indeed novel. The problem is how to get the current to flow through the part without also having to heat the electrodes carrying the current, which would take a very long time and would be essentially like soldering every connection with a cold soldering iron and waiting several minutes for it to heat up as you hold the tool in place. Unfortunately it seems that most materials that conduct electricity (and therefore can be used as electrodes) also conduct heat fairly well. In this case, conducting heat away from the part. Most importantly they also tend to have a high thermal mass — this means that they can “soak up” and store large amounts of heat energy as their temperature rises. This means lots of power wasted as the electrodes soak up heat you’d rather concentrate on the part, and a long delay for the tip temperature to rise and fall.

What they did was create a compound they’ve called “Athalite” which is really the sole innovation of the tool. No information is published about the actual composition of the material, but it appears to be a brittle, carbon-based “foam” that is both electrically conductive (as carbon naturally is), and has extremely low density and thermal mass. So, in theory, they can pump as much current as they want through the part, and when it heats up, the athalite tip won’t sap much heat away because it takes very little heat energy to raise its temperature. And presto, the solution to the problem. You only spend energy heating the part, not the tip, and when you pull the tip away, the current stops flowing and the athalite (having so little thermal energy stored) instantly goes from hot to cool. So, you can power the tool with AA batteries, and touch it seconds after making a solder joint. Just like in the commercials.

Unfortunately reality seldom emulates the magical world of advertising. In reality, the tool just doesn’t work for real soldering jobs, for which you’d want a portable iron. Remember the bit about ultra-low thermal mass? Well, it’s not only important for the tool, it’s also important for the part you’re soldering. Which means the ColdHeat might work well for tiny joints on a circuit board, but it’s lousy for anything bigger than that. Larger parts like automotive wiring, spade, ring and faston connectors, stuff you’re typically working with when you want a portable iron end up being too large for the gutless ColdHeat tool. Their large thermal mass makes it take forever for the part’s temperature to rise enough to melt the solder because the part itself is diffusing the heat and drawing it away. If the copper wire is beyond a given thickness (say about 16 gauge or so) then it will never heat up enough for a good joint. The tool just does not deliver enough power and what little heat is produced is conducted away too quickly by the copper wire. A simple task which can be handled by the cheapest of portable soldering irons is impossible for the ColdHeat.

But let’s get back to circuit boards. It should be fine there, right? No big wires, just small components with tiny leads, and thin circuit traces on the board. But, if you’re working on a circuit board, you’re probably already sitting by a proper, ESD-grounded soldering station with precise temperature control (as many modern electronic parts require, and which the ColdHeat does not offer) and have no real need for a portable, battery powered tool. And if you’re working on a modern electronic circuit, the prospect of massive electrical current flowing through a part of your circuit is NOT reassuring and in fact there have been reviews about this tool frying semiconductors, especially where the tip accidentally bridges multiple pins simultaneously. The current this tool has to pass to get a highly-conductive material like copper to heat up is truly impressive; the arc it often produces during operation is bright and like any electrical arc, it comprises a high proportion of eye-damaging ultraviolet light. Likely too small in this case to be a concern, but I would not want to have to look at that arc frequently.

Finally, let’s take a look at energy conduction. With a soldering iron, the energy you’re trying to conduct is heat — you’ve heated the tip, and you want to conduct that heat to the part to be soldered. The trick to doing this effectively is to wet the tip of the iron with solder. The liquid solder forms a higher contact surface with the part, and the heat transfers many times more quickly than if the iron were dry. Soon the part is hot enough to melt additional solder without direct contact with the iron, and the result is a high-quality joint that is both mechanically and electrically sound.

Now let’s compare this to the ColdHeat’s domain. The energy in this case is electrical energy, since the ColdHeat’s tip is only an electrical conductor. There is no heat to conduct from the tool to the part, in fact a small amount of heat energy flows the opposite direction from the part to the tool, this being unavoidable but minimized by the tip’s low thermal mass. Since the tip is made of such a hard, brittle substance, it does not conform at all to the part, and since the tip itself is not being directly heated, you can’t wet the tip with solder. So, you’re forced to deal with a very poor electrical contact, which makes some arcing unavoidable and slows down the task of heating the part. In fact, I was amazed at how difficult it was to get the ColdHeat to actually activate. It apparently detects continuity between the two halves of the tip and uses that as a signal to turn on the main power circuit, and even directly shoving solder into the gap would often not provide enough continuity to light up the red light on top which tells you it’s in heating mode. When a soldering tool can’t melt solder that’s being touched to it directly, it’s time to give up on the tool.

After about twenty minutes of trying to solder a single joint — a tiny 22-gauge automotive wire to a small faston lug — I had nothing to show but a ball of incompletely-melted solder stuck to the end of the copper wire, and no visible change to the lug. Certainly nothing approaching what I would call a successful joint. I felt like I’d been had. And to complete the story, though I was being gentle the ColdHeat’s tip accidentally slipped off of the part I was trying to solder, and tapped against a nearby metal surface. The tap was too much for the expensive $10 electrode, which broke instantly in such a way that the tool is now completely unusable. As shown in the picture, half the tip broke off leaving the other half, and the insulator. I could buy a new one, or for a couple more dollars I could buy a cheap butane iron that may not be as nice as my old Iso-Tip but that actually works and is less expensive than the ColdHeat.

I’m certain there must be some worthwhile uses for a substance like Athalite, but this is not one of them. Regardless of the interesting, novel and potentially useful properties of the tip material, the problems with the ColdHeat are predictable to anyone who knows how it really works, they’re easily demonstrated, and that this tool ever made it to become a retail product shows a level of dishonesty I find upsetting. There is no way this could be advertised as a functional product by anyone with a conscience — there are just too many things that a soldering iron can do that this product cannot. Like, just as an example, solder things. This lack of ethics and responsibility has been picked up by others as well, who have noted that the product listings on Amazon keep being regenerated, to try to hide the quantity of negative reviews. And oh, there are quite a few of those.

The bottom line on the Cold Heat soldering tool? No thanks. I’ll take actual heat instead.