Is it possible in 21st century Earth for someone to create a small super insulated box to store heat like an "anti-freezer" such as putting lava inside the box and the box not being hot to the touch because it is so insulated yet inside the box contains molten lava?

How small could this box be made and how much would it cost and what materials? I guess the ability to open this box and yet release the heat when desired would be the most difficult part.

  • $\begingroup$ A partial answer would be that such approaches are utterly essential to developing fusion reactions which generate power. $\endgroup$
    – Cort Ammon
    Dec 3, 2019 at 6:57
  • $\begingroup$ @CortAmmon-ReinstateMonica pulsed fusion designs rather avoid that issue, and may be more practical than continuous-burn type designs. $\endgroup$ Dec 3, 2019 at 17:20
  • $\begingroup$ Is containing lava a specific requirement, or just a random example of something very hot? Because liquid stone (lava) can be very chemically reactive / corrosive, and may chemically dissolve the inner surface of the container, even if the actual heat/temperature is not a significant factor in the reaction. So, are we talking about containing heat, and only heat, or lava specifically? $\endgroup$
    – Harthag
    Feb 22 at 0:07

5 Answers 5


You will need a high-temperature thermos.

@Surprised Dog gave an idea of making the inner part of it of tungsten. This may be good, but may be an overkill - the lava that we see erupting is never even hot enough to melt iron (melting point 1538 °C).

To prevent heat loss, the inner part of the vessel has no air, and reflective coating prevents radiating heat loss.

The big problem with thermoses is that they are designed to keep liquids that don't solidify at ambient temperatures. Even with slow heat loss, the lava inside will eventually solidify, and it would be very tough to get it out of the thermos. To prevent this, you will need a heated container.

  • $\begingroup$ Great idea, super thermos! I wonder how long you could prevent it from turning solid, because if you could have a super thermos with lava that you could hold without burning you it could be used as an emergency source of heat or energy by unscrewing it. 1 million years is good enough! $\endgroup$
    – CodeCamper
    Dec 3, 2019 at 4:02

The box would need to be a box within a box, with a vacuum in the gap but with a couple of layers of photonic crystals.

Heat transfers through materials via three methods:

  • Conduction (vibration of atoms)
  • Convection (energy transfer through gas)
  • Radiation (infrared light emitted by the hot material)

A vacuum would sufficiently deal with Conduction and convection, depriving the inner box of any direct way to influence the outside. A typical vacuum Thermos uses this method.

However, that does not deal with the infrared radiation, which Photonic Crystals are designed to absorb and/or reflect. Keep in mind the Sun, and how hot it is, is heating up our summer day with just infrared radiation. This would actually now make the box more insulative than space itself, which is only simply a vacuum.

You should then be able to pick up this box with no discernible, or possibly even measurable, heat from inside.


Silica based aerogel

Withstands temperatures of 1200 C and has very low thermal transmission.

Aerogel would not be durable enough on its own, so you would want to make an inner box of tungsten insulated with a layer of silica aerogel and an outer metal layer for durability. Something like stainless steel or titanium would work well.


Construct a cooler out of LI-900 tiles. The tiles used on the Space Shuttle for re entry.

They can withstand high heat, 1500 C and transmit very little heat through the tile.


  • $\begingroup$ Interesting! Are the properties of keeping heat out the same as keeping heat in though? $\endgroup$
    – CodeCamper
    Dec 3, 2019 at 4:03
  • $\begingroup$ Yes. It’s just a thermal insulator. Like an insulated mug. Keeps hot things hot and cold things cold $\endgroup$
    – Nate White
    Dec 3, 2019 at 4:04

The hardest problem with containing lava is finding a container that won't melt on contact. Tungsten is the metal with highest melting point of any element at 3422 degrees C. In fact, Tungsten has such a high melting point that if you throw liquid tungsten into lava, it will freeze.

So you will want to make your container out of that. Tungsten is not an insulator so my idea is to suspend the entire box from a long tungsten wire and then entomb the contraption inside a thick stone chamber. The stone will reflect the heat and insulate it from the outside world. Of course, there still will be loses, which is why you will need a small heating source at the base of the tungsten chamber to keep the heat up.

If you need a higher temperature, then you may have to investigate magnetic confinement, which is how experimental fusion reactors like ITER contain plasma at temperatures up to 100 million degrees.

  • 1
    $\begingroup$ While tungsten won't melt at high temperatures, it also won't prevent those temperatures from reaching its surface. It'll be solid, but superheated. $\endgroup$
    – Cadence
    Dec 3, 2019 at 2:49
  • $\begingroup$ @Cadence So hang the tungsten box from a tungsten wire. Make the wire long enough and it won't transmit too much heat to melt whatever the wire is attached to. $\endgroup$ Dec 3, 2019 at 2:51
  • 2
    $\begingroup$ @SurprisedDog the issue would be if the tungsten is radiating heat then wouldn't that mean the heat was rapidly escaping the tungsten box? $\endgroup$
    – CodeCamper
    Dec 3, 2019 at 3:19
  • $\begingroup$ @CodeCamper I suggest lighting a fire underneath the box to keep it warm. Make the tungsten thick enough and you won't have to use that much fuel to keep it warm. Place the whole contraption within a stone container (with a gap between stone and tungsten) to contain the radiated head from the tungsten box. $\endgroup$ Dec 3, 2019 at 4:00
  • $\begingroup$ This is a good core of an idea, but the radiant heat is going to be a problem. Ultimately, you need an insulator, and tungsten isn’t an insulator. $\endgroup$
    – SRM
    Dec 3, 2019 at 13:57

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