We all know to compress objects into smaller volumes, you would need to apply pressure to them. The required pressure depends on how strong the material is and which form is it (gas, liquid, solid).

I have a 10 cm3 block of steel in my room. I am always wondering how much pressure it would take to compress my steel block into one-tenth of its original volume.

If I built a special custom hydraulic press that could press on all sides, would it be strong enough? I have asked websites such as Reddit and Quora, but they never answer that correctly.

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    $\begingroup$ What is the purpose of this question? Why do you think that a hydraulic press will be able to exert enough pressure to do that? Why one-tenth? Which particular type of steel? Why not an element instead? $\endgroup$ Apr 16 at 3:54
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    $\begingroup$ "I have asked websites such as Reddit and Quora, but they never answer that correctly." How do you know? $\endgroup$ Apr 16 at 3:55
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    $\begingroup$ Do you mean your cube is 2.15 cm on a side, or do you mean it is 10 cm on a side? $\endgroup$
    – Fattie
    Apr 16 at 13:17
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    $\begingroup$ This question is confusing. The title question is seeking a theoretical answer while the body is seeking a realistic answer. This may be one of the causes of a non-definitive answer being provided. Its unclear what a definitive answer would be. Are you seeking an accurate and calculated pressure value that would compress steel to 1/10th its volume with associated factors or are you seeking a real world engineering solution to achieve said pressures capable of compressing solid steel to its maximum value before it phase changes? $\endgroup$
    – David S
    Apr 17 at 14:32
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    $\begingroup$ 10cm3 usually means a cube with 2.154cm sides. one-tenth of that volume would be 1cm3, which would be a cube with 1cm sides. So each side is only compressing 46.4% $\endgroup$ Apr 18 at 18:27

3 Answers 3


The basic answer is "Perfectly achievable pressures, but not for very long (with lasers, it's even legal)"

Metal is perfectly happy to shrink if you squeeze it hard enough. This is in fact the way that fission based plutonium nuclear bombs are detonated: the plutonium pit is squeezed to around 1/3rd its original volume by carefully timed explosive charges. (How much does the radioactive core of a nuclear bomb shrink due to compression by conventional explosives before it goes critical?)

On a related note, if you do successfully build an explosive vice to shrink your steel cube, be aware that you will probably have grey suited visitors.

I did notice that you asked for 1/10th the original volume, not merely 1/3rd. For this, conventional explosives won't really suffice. The solution to this conundrum is of course, more nuclear science. A fusion type nuclear weapon squeezes its secondary core using x-ray radiation from an initial fission explosion. The W-80 nuclear weapon allegedly reaches pressures of 140 TPa, https://en.wikipedia.org/wiki/Thermonuclear_weapon#Radiation_pressure . If you steal a w-80 and swap in your cube for the lithium deuteride fuel and then set it off, it will be adequately squeezed.

Finally, you could use lasers! Here's the chart of squeezing iron with lasers, they get it up to ~2x its original density at 1 TPa, but pressure required to increase density is rapidly increasing. enter image description here https://www.osti.gov/servlets/purl/1860794 However, this isn't nearly the peak pressure achievable at the National Ignition Facility. The top right graph only goes to 1 TPa because that's what's relevant for exoplanet studies. This experiment isn't even an implosion, they just hit one side of the sample with the laser/ Their fusion studies get to 100,000 times higher pressures and compress hydrogen to 100 times the density of lead, so they could very easily compress steel to ten times the density of steel https://en.wikipedia.org/wiki/National_Ignition_Facility. The disadvantage of this approach is that it could only compress a small portion of your cube, while the "steal a nuke" approach could probably squeeze the whole thing.

  • $\begingroup$ A great point! (But I'm wondering, aren't plutonium / lithium deuteride far easier to squeeze than steel?) $\endgroup$
    – Fattie
    Apr 16 at 15:01
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    $\begingroup$ LASERS - recall the OP wants to compress a TEN CENTIMETER WTF ?!?!? block (or possibly a 2.2 cm block, the Q is unclear). If I'm not mistaken this is not possible with laser cavities. (Or the answer would be "so it's a laser the size of the universe, and you need 256 of them" or such) $\endgroup$
    – Fattie
    Apr 16 at 16:33
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    $\begingroup$ Never forget that LASER stands for "Legal Amusement for Scientists, Engineers and Researchers". $\endgroup$ Apr 16 at 19:36
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    $\begingroup$ Cort Ammon suspects in his answer that the pressures required may cause fusion (even if that would be, may I add, endothermic with iron). Indeed, it's in the ballpark of the pressure caused by a nuclear explosion triggering fusion in a bomb. Is that a possibility, even if we increase the pressure gradually and remove the heat? My guess is not; the nuclei don't get really that much closer to each other. $\endgroup$ Apr 18 at 1:03
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    $\begingroup$ @Fattie: The question is not unclear! What is unclear is why people (myself included) assume the OP cannot be relied upon to calculate the volume of a presumably rectangular block of matter. $\endgroup$
    – peter
    Apr 18 at 8:45

The basic answer is "no, you cannot." Consider that if you have enough pressure to compress an "incompressible" steel to one tenth its volume, the surfaces doing the pressing experience the same forces, but in only one direction. The surface of your hydraulic piston will literally squeeze out the sides before you compress the steel.

But if you really want a number, we can make a ballpark estimate. Steel typically has an elastic modulus of 200 GPa. The pressure needed to deform this steel to 1/10th its size would be 10 times that much, 2TPa. That's a gross estimate, missing out on an astonishing number of factors. I would expect the real answer to be higher, but this is at least a number we can work with.

Turning to Orders of Magnitude (pressure), we can find pressures to compare against. The highest pressures we achieve in a diamond anvil are on the order of 0.6TPa. 5TPa is the kind of pressure we see in fusion experiments. Since I am certainly discounting all sorts of non-linear effects, it is very likely that you will reach the point of fusing atoms together before you generate the kind of compression you seek.

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    $\begingroup$ Crushing a car is very reasonable, because a car body is mostly air. All it has to do is bend the metal into a shape that has less air volume. Actually compressing solid metal (with no air volumes in it) is substantially harder. $\endgroup$
    – Cort Ammon
    Apr 16 at 5:06
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    $\begingroup$ @ZanMoon Eg, the Earth's inner core is (mostly) an iron-nickel alloy, with ~5% nickel. At STP, that alloy has a density ~8 kg/L. At the centre of the Earth, the density is estimated to be ~13 kg/L. To achieve much higher density, you need to put your steel block in the core of a star. Eg, the solar core density is ~150 kg/L en.wikipedia.org/wiki/Solar_core $\endgroup$
    – PM 2Ring
    Apr 16 at 6:45
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    $\begingroup$ @ZanMoon-chan Out of 3 standard states of matter, only gases can be easily compressed. Both liquids and solids would require huge amounts of pressure to compress even by a tiny amount. In practice, compressing any object is either pressurising gases contained (e.g. when you try to crush closed empty plastic bottle) or removing gases/liquids contained altogether (crushing opened bottle). $\endgroup$
    – matszwecja
    Apr 16 at 11:11
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    $\begingroup$ I think the threshold for fusing hydrogen and helium atoms is far lower than the threshold for fusing metals. Unless the steel has a significant quantity of hydrogen inside it, fusion is unlikely. $\endgroup$
    – nickalh
    Apr 16 at 12:33
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    $\begingroup$ @Fattie The highest pressures I am aware of outside of fusion experiments actually use diamond to compress the subject. For the particular kind of pressure that needs to be applied, diamond is stronger. But even those aren't sufficient for what the OP sought. $\endgroup$
    – Cort Ammon
    Apr 16 at 13:45

The bulk modulus of steel is 160 GPa, meaning that if it were linear, it would take 160 GPa to compress it twice. The pressure at the center of Jupiter is up to 7 TPa, which would be sufficient to compress steel 40 times, if the pressure/density relationship was linear.

It's not linear. Compressing matter 10 times takes even more pressure. Still, at some point, inside a large enough celestial body, it will be possible.

No need to ruin a perfectly good hydraulic press. It's literally as easy as flying to the nearest supergiant, dropping off your block of steel, and whistling casually like you have no idea how it got there.


  • $\begingroup$ Excellent reference! $\endgroup$ Apr 16 at 20:41
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    $\begingroup$ Isn't the block likely to find a layer denser than itself and thus basically "float"? $\endgroup$ Apr 18 at 1:30
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    $\begingroup$ @SoronelHaetir Only the very core of supergiants is iron and nickel, so the block will be very close to the center. Well, it won't stay in one piece of course... $\endgroup$
    – Therac
    Apr 18 at 5:57

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