As most of us know, the Heat metal spell is quite devastating anyone in metal armor. Look at the doffing times an it is a virtual death sentence.

Something this devastating will drive minds to contrive contingencies. The simplest contingency? Improve doff time. If you can get doffing down to say an action, that is a great improvement.

Is there a historic armor that is relatively quick to don and , more importantly to doff? I believe that the Logrica Segmentata and the Brigandine both would.

Both armors go on and off like vests. So, both should be easy to doff.

THE UPSHOT: The doff time for Logrica Segmentata and the Brigandine should be 1 full turn. Thus, if a soldier's armor was attacked with Heat Metal, they would be able to cut the bindings and drop off the armor if that is all they do with their turn.

The fact that Romans adopted and wore this to fight druidic Celts is just a wonderful historic coincidence that makes me like this idea even more.

QUESTION: The Brigandine is sheathed in cloth with the metal hidden from view. We know that mail shirts can be immune to the Heat Metal spell if they are worn under clothing. So, how does not seeing the metal of a Brigandine affect the Heat Metal Spell? Is it immune, should it give advantage on the saving throw. (I can see advantage and it taking a tiny bit longer to doff.)

Finally, if this has been sorted elsewhere, I would love a link to that. Thanks.

Quote from Solinoure >>

As most of us know, the Heat metal spell is quite devastating anyone in metal armor. Look at the doffing times an it is a virtual death sentence.

Something this devastating will drive minds to contrive contingencies. The simplest contingency? Improve doff time. If you can get doffing down to say an action, that is a great improvement.

Is there a historic armor that is relatively quick to don and , more importantly to doff? I believe that the Logrica Segmentata and the Brigandine both would.

Both armors go on and off like vests. So, both should be easy to doff.

THE UPSHOT: The doff time for Logrica Segmentata and the Brigandine should be 1 full turn. Thus, if a soldier's armor was attacked with Heat Metal, they would be able to cut the bindings and drop off the armor if that is all they do with their turn.

The fact that Romans adopted and wore this to fight druidic Celts is just a wonderful historic coincidence that makes me like this idea even more.

QUESTION: The Brigandine is sheathed in cloth with the metal hidden from view. We know that mail shirts can be immune to the Heat Metal spell if they are worn under clothing. So, how does not seeing the metal of a Brigandine affect the Heat Metal Spell? Is it immune, should it give advantage on the saving throw. (I can see advantage and it taking a tiny bit longer to doff.)

Finally, if this has been sorted elsewhere, I would love a link to that. Thanks.

I like the solution that metal armors would be "hidden" from view.

If plate armor then rather than cover yourself in a carpet, instead coating yourself in a lacquer makes the most sense. Lacquer is non-metallic, and if the objective is merely to hide the metal so the spell cannot be activated against it, then this is the most practical solution. Meticulously ensuring your armor is lacquered might be seen as the hallmark of a professional versus a careless "sellsword".

Quote from Solinoure >>

QUESTION: The Brigandine is sheathed in cloth with the metal hidden from view. We know that mail shirts can be immune to the Heat Metal spell if they are worn under clothing.

Citation?

Also, I think you're badly overestimating how common Heat Metal would be on a battlefield.  In most cases, the real counter to someone casting the spell is going to be "the soldiers who aren't the target of the spell fill you with arrows."

Brigandine Armor is well documented historic armor. Just google the term and you will see what it looks like. It is often confused with studded leather for it's similar appearance. The thing about Brigandine is the the plates are mounted to the inside of the coat. Leaving the cloth on the outside. It's a bit like wearing scale mail inside out. With brigandine, there are no large surfaces of metal to identify the object as metal.

"the soldiers who aren't the target of the spell fill you with arrows." I am afraid it is too easy to surprise cast this and go completely full cover and run away while their buddies close in. It's only a 2nd level spell and the casters will get away. Heat meat will make an army think twice about chasing opponents into forests, swamps and mountains. 

Quote from SimeonTor >>

Quote from Solinoure >>

As most of us know, the Heat metal spell is quite devastating anyone in metal armor. Look at the doffing times an it is a virtual death sentence.

Something this devastating will drive minds to contrive contingencies. The simplest contingency? Improve doff time. If you can get doffing down to say an action, that is a great improvement.

Is there a historic armor that is relatively quick to don and , more importantly to doff? I believe that the Logrica Segmentata and the Brigandine both would.

Both armors go on and off like vests. So, both should be easy to doff.

THE UPSHOT: The doff time for Logrica Segmentata and the Brigandine should be 1 full turn. Thus, if a soldier's armor was attacked with Heat Metal, they would be able to cut the bindings and drop off the armor if that is all they do with their turn.

The fact that Romans adopted and wore this to fight druidic Celts is just a wonderful historic coincidence that makes me like this idea even more.

QUESTION: The Brigandine is sheathed in cloth with the metal hidden from view. We know that mail shirts can be immune to the Heat Metal spell if they are worn under clothing. So, how does not seeing the metal of a Brigandine affect the Heat Metal Spell? Is it immune, should it give advantage on the saving throw. (I can see advantage and it taking a tiny bit longer to doff.)

Finally, if this has been sorted elsewhere, I would love a link to that. Thanks.

I like the solution that metal armors would be "hidden" from view.

If plate armor then rather than cover yourself in a carpet, instead coating yourself in a lacquer makes the most sense. Lacquer is non-metallic, and if the objective is merely to hide the metal so the spell cannot be activated against it, then this is the most practical solution. Meticulously ensuring your armor is lacquered might be seen as the hallmark of a professional versus a careless "sellsword".

 I can see that. Lacquers, or elaborate tabards and robes. Or perhaps special clothing designed to contain and hide the armor.

Hiding is a bit what the brigandine is about since it shows the cloth and the holds the plates to the body .

I know what brigandine armor is.  I'm asking for a citation that wearing cloth over metal armor makes you immune to Heat Metal.

And you're vastly overestimating how much effect the spell has vs an army.  A Medieval army would have hundreds or even thousands of soldiers in it.  They're going to have people who are actually looking for trouble and sooner or later someone's going to spot you no matter how good your stealthiness is.  And that's ignoring that the army itself could also be employing spellcasters of its own to counter you.  Best case scenario is that you take out one soldier, and that's no more effective at taking out an army than using a pair of tweezers to move one grain of sand is going to get rid of a sand dune.

If Heat Metal was common enough, I guess most armor would be designed to counter it: Steel plate with copper cooling flanges on the outside, and heat-resistant wool on the inside. Should be available from reputable armorers everywhere.

Edit: Or aluminum? It strikes me that the heatsink on my cpu is aluminium, not copper. Whatever, I'm no engineer, I don't need to know this stuff =)

Quote from 6thLyranGuard >>

I know what brigandine armor is.  I'm asking for a citation that wearing cloth over metal armor makes you immune to Heat Metal.

I assume they're basing it on this:

Choose a manufactured metal object, such as a metal weapon or a suit of heavy or medium metal armor, that you can see within range.

But do you need to be able to see the metal bits specifically, or just the armor itself?

Yeah, that's the sticking point.  Given that certain magical armors like a mithral breastplate are noted as "being able to be worn under regular clothing, I believe that it indicates that by default, armor cannot be worn under clothing and therefore the trick of covering yourself up in cloth wouldn't work.

I agree that the evolution of weapons and armor wouldn't likely change much due to Heat Metal spell, for reasons already addressed. Countermeasures such as battle tactics and spells cover this pretty well.

Regarding armor construction methods intended to render Heat Metal ineffective: RAW, the spell has a range, is line of sight only, and it affects an object made of metal. At my table, I rule that one could cast the spell at the target's chest, for example, and affect the first metal object or contiguous metal assembly reached in that (call it 1foot diameter, 30cm)target area, within range. If there is no metal within that direct line of fire and range, the spell is wasted. One can agree that armor under-padding (better word?) offers X points of insulation, as it heats up and burns first. Padded asbestos long johns? Neat idea, but slow death by another means. Also, who made the underwear for you? 

As far as how one might shed armor quickly, I could see quick-release buckles and straps being made using medieval methods, but how does one prevent accidental release during close combat? Added complexity, more time to get out. Then there's the layering problem. Say a hidden breastplate is affected, and gets red hot. The affected PC has to drop everything resting on, strapped around, and dressed over that breastplate, in order to get to those leather straps or quick-release buckles.

Drop the bow and quiver, unbuckle the belt around your cloak and drop it, shed the cloak, release your weapons belt or harness and drop it. Yank off your shirt(s), and doff the hot breastplate. To do this fast, one must practice it. To do this in a mass battle, one opens themselves up to becoming the next pincushion on the field.

The other issue is if you have some sort of quick-release mechanism for your armor, opponents can theoretically attempt to use it against you in close combat.  And the question then becomes is the ability to quickly ditch your armor in the event of a hostile party casting Heat Metal on you worth the liability of accidental or purposeful release of your armor while in melee?