Heat-stained metal, the right way.

How should we paint heat-stained metal?

I’m just going to come out and I say this… I think the hobby community has been painting that discolored hot metal (aka heat-stained, heat-soaked or annealed metal) effect the wrong way around. In every tutorial or example I’ve seen, it’s painted towards the barrel of the gun. After all, it looks cool and makes it clear that’s the business end, if there was any doubt.

I’ll start off saying I doubt this article will get much traction. It’s not even ‘wrong’ to paint them however you want, per se, and the rule of cool has a lot to do with it. But we, meaning the hobby as a whole, are doing heat-stained gun barrels backwards in my opinion, and I think we ought to talk about it like it’s actually a real issue that matters (they’re just toys, I know, but I’m a geek and this shit keeps me up at night).

Heat-stained tailpipesI’ve been thinking about it ever since I did my Knight, since that’s the first time I’ve attempted to paint heat-staining on anything. At that time I watched some videos online and looked around at some reference material, and the heat staining always come from the source of the heat. I know it sounds obvious but we never seem to paint our guns like that. I didn’t think about it much at the time, but now I’m seeing more and more people use the technique and it’s starting to bug me.

Painting heat-stained metal on exhausts

Heat-staining diagram for tailpipesIf you look at engine exhaust from cars and motorcycles like the picture above, the discoloration occurs right where it connects to the engine. If there are curves in the pipes you’ll see some there as well, because it catches the heat. You’ll occasionally see it on the very tips of car exhaust, but that seems to be a cosmetic thing cause by a different metal on the tips. That said, when wargaming folks paint heat-staining they usually focus it on the front of the barrel. I’m not really sure why that is.

Heat-stained brass on Thermal CannonOn my Knight, I added a heat-staining effect to the brass-colored heat shroud around the pipes. I figured at the time that the pipe material was probably an alloy that could withstand the heat without discoloring (a sign that the metal is under a lot of stress), as these machines are built to last thousands of years. The shrouding, however, is there partially to more quickly diffuse the heat, which means it would need to be more conductive and therefore, in theory, susceptible to the annealing process that produces the discoloration. Phew! That’s a lot of BS logic for a model… But bear with me.

Heat-staining on a motorcycle exhaustOn a dreadnought, for instance, you might see the heat-staining starting at the bottom where it connects to the torso and working its way up the pipe, like the image here. Whether you do it on the pipes or the shrouding, or both, is totally up to whichever you think looks the best. That would mean the soot staining we see around the tips of the exhaust would be a totally separate process from the discoloration caused by heat. When I say it like this, it makes perfect sense to me and I wonder why I never really thought about it before. Very few people even seem to do those pipes anyway, including myself. Usually you see it on weapons.

Painting heat-stained gun and cannon barrels

Guns are different from car exhausts. Duh. But the heat pretty much works the same way: there’s a clear source. Even in a science-fiction environment, we can make some assumptions about how they might work. We know many guns like bolters, stubbers, assault cannons, etc. fire a shell from the breach, which then travels through and is expelled from the tip of the barrel.

Heat pattern on minigun barrelStubbers and assault cannons seem pretty analogous to their real-life counterparts, and luckily we can actually see how those suckers glow. What I find from looking up reference material shows the glow starting at the rear of the gun, and as they’re continuously fired, the glow works its way forward. Some miniguns have a slightly cooler band towards the rear, which means they really should have the heaviest color between a quarter to half-way down the barrel. Yes, eventually the entire barrel gets hot, but that’s not very dramatic to paint, is it?

Bolters may be a little different, as they are supposed to be two-stage weapons that fire an initial charge to clear the shell from barrel before an internal propellant ignites outside the gun. It would make a lot more sense to ignite that second charge inside the barrel for accuracy’s sake, but space magic, peeps. Space magic.

Gun barrel glowing red-hotIn rapid-fire guns, the heat is clearly focused towards the breach end of the barrel. I actually found a scientific study that measured the temperature along the barrel as guns were fired, and it showed much higher temps towards the breach with a pretty steep drop off. Again, looking at real-life examples of guns fired at night, the effect is quite clear. The heat stress is most pronounced at the rear of the barrel. That means we’re collectively painting it backwards on many of our models, if we care about trying to make anything somewhat realistic.

Different guns may heat up in different ways

This seems obvious, but let’s look at a few common examples. Flamers, for instance, don’t even ignite the fuel until it clears the barrel so there really should NEVER be heat staining anywhere but at the front, so I think we’re doing those correctly. I’m pretty sure the first examples of the heat-staining technique I’ve ever seen were flamers, so that’s probably why we always paint it towards the tips on other guns.

Melta guns are up for some debate. I’ve heard some folks say there’s some kind of chemical reaction that takes place when it meets the air, so then it would look like flamers. They’re supposed to be based on microwaves, but I’m not sure how that would actually work. I always imagined a superheating chamber of some kind within the gun itself, which then expels this hot air out the tip. This is why I painted my Knight’s thermal cannon with the heat towards the rear, just like a gun breach. I think of it sort of like a jet engine (also hottest at the base), mostly because of the way the melta rules make it most effective at very short ranges. To me, that makes sense.

Plasma weapons are really up in the air. I guess we all assume the coils are the hottest part, but what happens to the heat as it travels through the bulbous tip? Would the thickest metal at the rear be the most resistant to the heating effect? If so, it would make sense to tint closer to the barrel. Or do we think the heat disperses rather quickly after exiting the coils? If that’s the case it would make sense to add the heating effect towards the back. I’m really not sure about this one. I think rule of cool might decide this, but I haven’t painted a plasma gun since I started thinking about it.

Some guns, like maybe las weapons, don’t really seem like they would exhibit a heating effect at all, but I regularly see them painted that way. If anything I’d make a case that the powerful energy source would cause the most heat, so that would mean the base of the barrel, again. Traditional cannons on tanks (and Knights), in my opinion, would definitely be hottest at the base of the barrel, not the tip. Same for missile launchers (though there would be a backwash of heat from the jet on the missile itself). I could go through each weapon here but I think I’ll leave that all up to you to ponder as you paint.

As for xenos weapons, I really have no clue… Some of them, like the Tau weapons, seem more or less grounded in traditional weapons. Maybe rail guns wouldn’t produce much heat as the particle sort of floats through the magnetic chute? Our modern rail gun prototypes produce more heat toward the tip, if I remember correctly, as the shell accelerates and causes friction with the air around it. What about Necron gauss weapons? Shuriken catapults (I don’t think wraithbone would heat like that) and such? Comment down below if you want to make a case for any of them.

So should we start painting it the other way around?

In conclusion, I want to repeat that I doubt my article will really change the game here, much. I’m not the kind of jerk that will start calling it out on Twitter when I see them, and frankly I’m not even 100% sure which way they should be painted. Logic seems to point one way, though, if you’re shooting for realism. No pun intended.

These are, after all, fantasy weapons. But, I have seen a lot of tutorials and examples of weapons painted with the heat staining at the ends of the barrel. ForgeWorld even does it with their tanks. Maybe some people can tell me if this is actually something they’ve seen in real life, but I couldn’t really find any reference material online and I don’t have access to a tank gun, unfortunately.

What do you think? Do you really care about this, or am I overthinking it? Actually, I already know I’m overthinking it… You don’t have to answer that one.