In a fantasy setting I'm working on for an RPG, I was trying to determine what properties I could use to determine how well metals resist magic and how readily they absorb enchantments based on something measurable in the real world. Then it hit me, conductivity.

The rule: More conductive metals would be able to soak up more magic before being saturated, but would also be more vulnerable to magic damage. Less conductive metals would resist magic damage, but could not hold as powerful enchantments.

Going off a world that has the equivalent of ~14th century metallurgy and blacksmithing techniques, which metals would be favorable for magic resistant armor? And which metals would make for the best enchanted weapons and armor?

Keep in mind, they still need to be able to be light enough and durable enough to function as armor and weapons (otherwise I think gold and silver might win in the enchanted category.)

Clarification: The conductivity rule is only for metals. I'm going to work out a different measure for non-metals.

  • 4
    $\begingroup$ Is non-metallic armor like boiled leather up for consideration? $\endgroup$
    – Alexander
    May 4 '18 at 23:55
  • $\begingroup$ Best electricity conductors in widespread use in the 14th century were silver, copper and gold (in this order). Worst was iron, about 6 times less conductive than silver. Steel was rare, and is about 60 times less conductive than pure iron. Look at the table graceously provided by Wikipedia. $\endgroup$
    – AlexP
    May 5 '18 at 0:28
  • $\begingroup$ I'm only applying the conductivity rule to metals. That chart is great! $\endgroup$
    – Arvex
    May 5 '18 at 3:11
  • $\begingroup$ Fun flavor suggestion: for armor that tries to meet a middle ground between physical defense and magical enchantment, you could have steal that is inlaid with copper/gold. That gives you a great mechanical excuse for a cool-looking cosmetic feature. You can see lots of gorgeous examples of medieval armor inlaid with precious metals, but I believe these were mostly for ceremony, not war. However in your world, there might be a real utility need for this craft! $\endgroup$ May 5 '18 at 15:08
  • $\begingroup$ What would happen of you built capacitors into your shields? $\endgroup$
    – John
    Apr 16 at 4:04

This is an interesting question.

All metals conduct reasonably well. Besides, your knights want to look good! They want to feel important! They want silver and gold on their armor, which would be like lightening rods to magic.

But... what if we coat the armor? In an ideal world where all materials were present, if you coated the inside of your armor with rubber (a wonderful insulator), then you'd have armor that could withstand sword and wand alike and sill make the knight feel grand!

On the other hand, if we assume all materials aren't present and we only have access to those materials available in medieval Europe...

  • Laquer could be applied to rigid armor, such as plate mail.

  • Leather would be an inexpensive and easily available insulating material, but when wet it conducts just fine (salty sweat is not your friend).

  • Plant fiber is a reasonable insulator, and it wouldn't be quite so susceptible to sweat. Would wear out quickly, though. as in, decompose.

I've got it!

Layered satin or silk would probably do the trick. And your knights would look smashing at the same time. Those layers would still become more conductive with sweat, but the trade-off is they'd last longer than plant fiber, wouldn't chaffe like leather, would breath almost like Egyptian cotton, and would look good.

In fact, you'd look a bit like a Roman soldier.

  • 1
    $\begingroup$ Realistically, as long as the metal bits connected to each other and then had a grounding rod in each foot (a short metal spike or three, kind of like cleats) and you wouldn't need much in terms of insulation (electricity flows across the surface of metal, not through it) beyond not wanting to chafe (or get burned: the lightning does heat up metal pretty good). Which means.... chain mail! $\endgroup$ May 5 '18 at 3:59
  • $\begingroup$ @Draco18s I don't think it should be assumed that just because magic is resisted like lightning, it automatically moves exactly like it and can be negated with lightning rods. $\endgroup$ May 5 '18 at 12:31
  • $\begingroup$ Magic won't be behaving like electricity. I'm just using conductivity as a measure to determine which metals are more vulnerable and resistant to magic. $\endgroup$
    – Arvex
    May 5 '18 at 12:52
  • $\begingroup$ Why would plant based armor decompose? I know that's the explanation for why it's hard to find plant-fiber armors like Linothorax in archeological digs, but it's not like these knights are going to store their gear in a pile of dirt. $\endgroup$ May 5 '18 at 15:11
  • 1
    $\begingroup$ @Arvex in which case, metal is an awful choice for armor. As in, the worst. Most metals are around 5*10^-8 Ohms of resistance (that's 0.00000005!), drinking water is 20, and air is 1.3*10^16 (13000000000000000!). Of all metals I can find numbers for easily, Stainless Steel is "the best" at 6.9*10^-7 (with Silver the worst at 1.6*10-8). Mercury is better, but a liquid at room temp. $\endgroup$ May 5 '18 at 18:31

I assume you meant resistivity (which is the property of the material) not resistance (which is the property of the object), since we are comparing different metals.

Since you mentioned that this only applies to metals, I will not consider semiconductors like Silicon and Germanium either. Nichrome has a very high resistivity, almost 60 times of that of Copper. Due to its high resistivity, it is also most widely used as heating elements, for instance in electric kettles. Wikipedia tells me that it is usually "80% nickel + 20% chromium". Unfortunately both were not discovered until the 1700s.

If you are unwilling to ignore the historicity, then we have to only look at the metals that were known to us in the 14th century, which were not many:

  • Arsenic (metalloid): 3×10-7 m Ω
  • Antimony: 4×10-7 m Ω
  • Tin: 1.1×10-7 m Ω
  • Lead: 2.1×10-7 m Ω
  • Zinc: 5.9×10-8 m Ω
  • Copper: 1.7×10-8 m Ω
  • Silver: 1.6×10-8 m Ω
  • Gold: 2.2×10-8 m Ω
  • Mercury: 9.6×10-7 m Ω
  • Iron: 9.7×10-8 m Ω

So the winner seems to be Mercury (though it is a liquid in rtp).

The winner that is a solid in rtp is Antimony.

(Could not find much information on alloys though.)

  • $\begingroup$ Antimony honestly sounds like a metal that would have some sort of special relation to magic too. That's a pretty happy coincidence. $\endgroup$ May 5 '18 at 14:16
  • $\begingroup$ The setting isn't 14th century. I'm just using the 14th century metallurgy to establish a baseline of what metals are available. I might introduce other metals if I believe that the means I've established in the setting can reach them. I may or may not go further back. $\endgroup$
    – Arvex
    May 5 '18 at 18:25
  • 1
    $\begingroup$ @Arvex you may find this useful: en.wikipedia.org/wiki/Timeline_of_chemical_element_discoveries; the "purple" metals were all found in the 1700s. $\endgroup$
    – Lowell
    May 6 '18 at 6:19
  • $\begingroup$ @JasonClyde I disagree with that notion, as in alchemy it is the grey wolf which eats the king leaves back the crown, as it's one of the few ways to separate gold and silver. I would imagine that that would give it some relation to magic. $\endgroup$ Apr 14 at 22:36

Iron Nickel Alloy

While our pre-modern ancestors did not know how to isolate Nickel from Iron to create these alloys in a controlled manner, Meteorite Steel has been used by man since the early bronze age. Some of these natural alloys contain around 30% Nickel. Iron Nickel alloys in this range typically have an electrical resistance of about 8.15E-7 m Ω giving it a higher resistance than any pure soild at room temperature metals known before the 14th century.

... or rusted iron depending on your definition of "metal"

If you allow for metals alloyed with non-metals, you could also consider using rusted iron armor. While rust was normally avoided by the medieval knight, metal oxides typically have electrical resistances that are orders of magnitude higher than pure metals. So if you want to make your breastplate able to stop a magic attack, just leave it outside in the rain for a few weeks. That thin rusty exterior will offer more resistance then the entire remaining width of breast plate.


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