Hal. Posted March 13, 2011 Share Posted March 13, 2011 Could I first make it clear that a container exists which will be able to withstand whatever pressure I put on it , so it need not be considered here for the purpose of the following ? Assuming I can , I shall also assume that at the centre of this container I can place a normal , regular , ordinary egg which is not being supported by anything . If the egg was surrounded by air and a facility existed which could allow me to vary the pressure in the container , what type of a Maximum Pressure ( in psi or bar or n/m^2 or indeed hectopascals if need be ) could I expect to get before the egg cracks ? Thanks to all in anticipation of replies ! Link to comment Share on other sites More sharing options...
Danijel Gorupec Posted March 14, 2011 Share Posted March 14, 2011 I suppose that you 'must' keep surorounding pressure equal from all directions (otherwise it would be possible to produce dinamic pressure differences - sound waves - that would break the eggshell apart). If I am correct, the eggshell permits air, so you will have your chance only if you change the air pressure really rapidly. Still, it would not be easy at all. Maybe, it would be easier to rapidly decrease pressure than to increase - the eggshell should be easier to break from inside. So, maybe the easiest recipe would be to slowly increase pressure and then rapidly decrease it. I cannot give you any numeric value, sorry. Another idea... if temperature can be increased (by pressure increase), you may boil the egg. Boiled eggs break sometime. If you do it rapidly enough, steam from the inside might explode the egg. Link to comment Share on other sites More sharing options...
CaptainPanic Posted March 14, 2011 Share Posted March 14, 2011 Mother nature has designed eggs to be able to breathe (which is quite a good idea if an egg is meant to be the home for a developing animal). So, if you increase the air pressure slowly, it will never break. If you increase it rapidly, then probably just a few mbar will be sufficient to break it. Why don't you just take an egg, and put some weights on it to see when it breaks? It's not a very precise answer, but then again, the quality of egg shells (depending on the diet of the chicken) is probably quite huge too. Link to comment Share on other sites More sharing options...
Hal. Posted March 14, 2011 Author Share Posted March 14, 2011 (edited) I would like to proceed on the assumption that the egg will crack . Theories or facts describing otherwise are welcome . What I am trying to do is to imagine some circumstances for an experiment . If I make my container to fail at 25 psi absolute this may well be a lot of work for nothing , if the egg is still structurally fine near to this pressure . If I make my container to fail at 50 psi absolute then this may also be a lot of work for nothing , if the egg is uncracked near to this pressure . I don't want to excessively shock the egg . I want to apply the pressure slowly and see what happens . If the egg can withstand 100 psi absolute then my container must also . If on the other hand I make a container to withstand 500 psi absolute and the egg happens to crack at 25 psi absolute , I'll be cursing my expensive spending on my strong container . Although on second thought's , my strong container could have other future uses . I see there are suggestions that the air can leak into the egg . Can the contents of the egg also leak into the air ? ( A kind of egg gu / air flow through porous eggshell ! ) I would try to make sure that no amount of heat big enough to cause rupture from within can happen . ( An interesting concept ! ) Anybody reading this should always remember the important things in life . Be careful around high pressure objects . Edited March 14, 2011 by hal_2011 Link to comment Share on other sites More sharing options...
InigoMontoya Posted March 15, 2011 Share Posted March 15, 2011 (edited) I don't want to excessively shock the egg . I want to apply the pressure slowly and see what happens . If the egg can withstand 100 psi absolute then my container must also . If on the other hand I make a container to withstand 500 psi absolute and the egg happens to crack at 25 psi absolute , I'll be cursing my expensive spending on my strong container . Although on second thought's , my strong container could have other future uses . I see there are suggestions that the air can leak into the egg . Can the contents of the egg also leak into the air ? ( A kind of egg gu / air flow through porous eggshell ! ) You may certainly proceed under the assumption that the egg will crack, but I am with the others in the belief that this assumption is invalid and makes every statement made under it suspect at best. As others have said, eggs are porous and will leak air. Don't believe us? Do a very low cost experiment: Put an egg in cold water and SLOWLY heat it up to (say) 150 F. As the air inside the egg expands due to increased temperature, air will leak out. Note that boiling is a long ways away so you aren't seeing steam bubbles. SOoooooo.... One more time: If you apply pressure *slowly* the egg will not crack under static air pressure. Ever. As for the question of whether or not the egg contents will leak out... Yes, the moisture (ie, water vapor) can migrate out, but that's the only thing you'll find leaving the shell barring large pressure differentials. Edited March 15, 2011 by InigoMontoya Link to comment Share on other sites More sharing options...
Hal. Posted March 15, 2011 Author Share Posted March 15, 2011 (edited) There are only 2 choices I have , namely to assume that the shell will crack or to assume that the shell won't crack . If I assume that the shell won't crack then my experiment is pointless and effectively over before it has begun . I will have not conducted an experiment and I will be no nearer designing a container to test shells . I accept that the shell may withstand a high pressure which could be beyond anything that I can apply to it at a reasonable cost . But , to say that the shell will not crack ever is a statement that to me implies infinite pressure . I can't apply infinite pressure , of course . So , if I happen to apply a pressure of 100 psi absolute and measure the pressure properly to confirm this and also see that there is no damage to the shell and also have a container at the end of it which will be designed to withstand 100 psi absolute with a significant margin of safety , then I will have progressed my experiment . I would not assume from such an experiment that the shell will never crack . Who knows what sort of a weird phenomena may suddenly occur in shells at heightened pressures . I would only have confirmed to myself , that under my conditions of experiment on that day , I found a shell which was able to withstand 100 psi absolute . I now know that shells are porous which I did not know before I asked about them here . So I had never previously thought that anything I was looking at while cooking one was originating from within it . I will definitely put a thermometer in a pot of water at 150 F ( 65.55 deg C approx. ) to see with my new knowledge what is going on . Anybody reading this should always remember the important things in life . Be careful around high pressure objects . Edited March 15, 2011 by hal_2011 Link to comment Share on other sites More sharing options...
John Cuthber Posted March 15, 2011 Share Posted March 15, 2011 (edited) I'm not sure the egg will crack at any reasonable pressure. I think it will squash slightly. Initially the egg will compress roughly evenly in all directions and the airspace in it will get smaller. Eventually the airspace will be crushed to nothing or dissolved. You can generally stretch ceramics (and eggshell looks a bit like a ceramic to me) by a % or so before it cracks, but they are relatively weak in tension because they have cracks that open up and become fractures. In compression they should be much stronger. With a 1% change in linear dimensions it would shrink by 3% by volume and I think that's about the size of the air space ( which is rather variable anyway). I think the shell can elastically deform enough to shrink the airspace to zero. Anyway, back to our squashed egg. It's now a thin layer of ceramic with hight pressure stuff on the outside and also on the inside. In the same way that my chest is able to support the massive forces on it due to air pressure, because it also has air in it at much the same pressure, I think the eggshell is now unlikely to break. Edited March 15, 2011 by John Cuthber Link to comment Share on other sites More sharing options...
michel123456 Posted March 15, 2011 Share Posted March 15, 2011 (edited) A boiled egg floats, but a fresh egg sinks. So you can go at sea and sink a fresh egg to make your experiment. Unless you want pressure by air and not by water. It is supposed impossible to break an egg by pressing in the palm of a hand. Be careful doing the experiment. Edited March 15, 2011 by michel123456 Link to comment Share on other sites More sharing options...
Hal. Posted March 16, 2011 Author Share Posted March 16, 2011 Isn't the egg a complex thing altogether ? We could probably find volumes of studies about it if we looked and take lifetimes to try to understand it's inner workings . The wiki describes chicken eggshell as being .................. " 95 - 97 % Calcium Carbonate crystals , which are stabilized by a protein matrix . Without the protein the crystal structure would be too brittle to keep it's form " . They also think at the wiki that .................. " lower protein compositions are associated with lower shell strength " . Calcium Carbonate is an ingredient in some cements . So , it has a reputation for use as one ingredient in high strength materials ( relatively speaking ) . Another source suggests that chicken eggshell is 95 % Calcium Carbonate and the remaining 5% includes Calcium Phosphate , Magnesium Carbonate and soluble and insoluble proteins . The composition of a shell is like an index of a chemistry book . I think to bring an egg under water to apply the pressure is not what I want to do if I don't have to . I did a calculation which concludes that I must take an egg 10 metres ( give or take a few centimetres ) under seawater to add 1 atmosphere of pressure to the 1 atmosphere of pressure it would already be at , at the surface , to give me 2 atmospheres of absolute pressure at this depth . 10 metres is about 10 metres too many for me in seawater . I suppose an apparatus could be made with some hoses , a bucket with view window , some seawater and a 3 storey building to get the same absolute pressure without too much danger . Pistons , weights and seawater could be an alternative . Again , don't injure yourself following your dreams ! Link to comment Share on other sites More sharing options...
michel123456 Posted March 17, 2011 Share Posted March 17, 2011 (edited) The chemical composition of the shell is one thing that concerns the resistance of material*. The shape of the shell is another thing. The shape makes the forces to act under pressure inside the thickness of the shell. Have a look at vault or shell strucures, and at "funiculaire des charges" sorry I am lost in translation. In your case, pressure exerts force always perpendicular to the surface, unlike the diagram. The result keeps the resultant vector tangent to the surface which means the shell is under compression and will crack only in 2 situations: _when the pressure inside the material will exceed its resistance. _when the resulting vector change direction and gets no tangential anymore. That happens when pressure is not uniformly applied all around. In your case that will happen at the air cell inside the egg shell. *material resistance is an easy course involving elementary physics, you can get your head around in about 1 or 2 years of cursus. Engineers need 4 or 5 for structural applications. But I doubdt you will find easily information about basic properties of organic materials. Maybe in specialized engineering for medical purpose. -------------------------- Shell structures is a very interesting subject. You encounter these not only in buildings, but in any kind of objects, like a bottle of coke for example. Edited March 17, 2011 by michel123456 Link to comment Share on other sites More sharing options...
Hal. Posted March 20, 2011 Author Share Posted March 20, 2011 Egg ! Link to comment Share on other sites More sharing options...
forufes Posted March 25, 2011 Share Posted March 25, 2011 i think the egg will withstand an unimaginable amount of pressure, since it's applied evenly from all sides. Why don't you just take an egg, and put some weights on it to see when it breaks? It's not a very precise answer, but then again, the quality of egg shells (depending on the diet of the chicken) is probably quite huge too. no, this is extremely inaccurate, when you put weights on an egg you're multiplying the stress into a concentration factor, a big one. when the egg undergoes pressure from all sides only normal stress will be developed, however when you apply a weight or hit it against something there will be shear stress, and that is what will break the shell. it's like the difference between trying to crush a wooden plank under even weights and fixing it from the sides and applying the same weights to its middle. Link to comment Share on other sites More sharing options...
CaptainPanic Posted March 25, 2011 Share Posted March 25, 2011 i think the egg will withstand an unimaginable amount of pressure, since it's applied evenly from all sides. no, this is extremely inaccurate, when you put weights on an egg you're multiplying the stress into a concentration factor, a big one. when the egg undergoes pressure from all sides only normal stress will be developed, however when you apply a weight or hit it against something there will be shear stress, and that is what will break the shell. it's like the difference between trying to crush a wooden plank under even weights and fixing it from the sides and applying the same weights to its middle. Then why don't you make some mold, so that you distribute the forces to a much larger area? I never suggested that you concentrate the entire weight onto a single spot. It's still inaccurate, but you'll at least get an order of magnitude. Who knows... maybe the pressure is just a few mbar, and then you can create a pressure chamber with household equipment. Or you learn that it's several bars, and then you have to find a very different solution. Link to comment Share on other sites More sharing options...
Hal. Posted March 25, 2011 Author Share Posted March 25, 2011 This is Franc Grom who from what I see is an expert with eggs ! Link to comment Share on other sites More sharing options...
Danijel Gorupec Posted March 26, 2011 Share Posted March 26, 2011 This is Franc Grom who from what I see is an expert with eggs ! Must be that Franc Grom is an expert in egg-breaking. I guess that he uses following techinques to break an egg: He uses container half filled with special oil. He puts the egg into the oil. The oil he uses will not pass through the eggshell even under high pressure. At the same time, the oil has the same density as the egg, therefore the egg is perfectly supported from all sides. He then slowly increases pressure of the air above oil, until the egg breaks. When Franc Grom doesn't want to mess with oil, he simply warps an egg into airtight foil. He probably calls this a "quick-method". Link to comment Share on other sites More sharing options...
michel123456 Posted March 26, 2011 Share Posted March 26, 2011 (edited) Why would he do that? You can insert a pin into a fresh egg without further damage. Also I suspect that Mr Grom don't use eggs from the supermarket. It is well known that the fragility of the shell is related to its thickness, and that "The variation of breaking strength and thickness of eggshell is the least at the time of heavy egg production" You could ask a farmer instead of looking in Wikipedia. He would also probably say that the thickness is related to nutriments. Edited March 26, 2011 by michel123456 Link to comment Share on other sites More sharing options...
Danijel Gorupec Posted March 27, 2011 Share Posted March 27, 2011 Why would he do that? Michel, I was actually joking because (I felt) this thread went too odd... I have no idea how this artist realy make his stuff (but I like it). Link to comment Share on other sites More sharing options...
boogieman Posted April 26, 2011 Share Posted April 26, 2011 A boiled egg floats, but a fresh egg sinks. So you can go at sea and sink a fresh egg to make your experiment. Unless you want pressure by air and not by water. It is supposed impossible to break an egg by pressing in the palm of a hand. Be careful doing the experiment. Hal - michels suggestion has some merit. Where I live (and fish), we get sea depths of 200meters (284 psi) within 12 kilometers of land. Simply by attaching the egg to your sinker and sending it down to pre-determined depths will be able to determine what pressure it will crush at. NO expensive container required!! This will cancel out the "air leaking in" effect as discussed in other posts, and if WATER ingress is a problem, cling-wrap or varnish will solve that as well. If you WANT the "air leaking in" scenario, putting the egg inside a plastic bottle may work. Gonna need a larger sinker though. The cap staying on might be your biggest problem. I may even try this myself the next time I got out, will let you know - lol Link to comment Share on other sites More sharing options...
baxtrom Posted May 4, 2011 Share Posted May 4, 2011 Hmmm.. if egg contains egg white + yolk, any external pressure evenly distributed over the egg would be balanced by hydrostatic counter-pressure from the near-incompressible (?) fluid inside, and the only resulting stress would be through-thickness compressive stress (not too effective for cracking the shell wall). If as by magic (or needle) egg is empty, it's a different question. Link to comment Share on other sites More sharing options...
CaptainPanic Posted May 4, 2011 Share Posted May 4, 2011 Hmmm.. if egg contains egg white + yolk, any external pressure evenly distributed over the egg would be balanced by hydrostatic counter-pressure from the near-incompressible (?) fluid inside, and the only resulting stress would be through-thickness compressive stress (not too effective for cracking the shell wall). If as by magic (or needle) egg is empty, it's a different question. All eggs have an airpocket (or egg sac, egg cell), and therefore cannot be considered incompressible. Link to comment Share on other sites More sharing options...
baxtrom Posted May 4, 2011 Share Posted May 4, 2011 (edited) All eggs have an airpocket (or egg sac, egg cell), and therefore cannot be considered incompressible. Right, so back to drawing board. Engineering approach: first of all, recognize relative complexity of egg geometry (egg shaped!) and imagine instead a spherical egg, as an approximation. Assume diameter of [math]d [/math] = 50 mm and wall thickness [math]t[/math] = 0.3 mm (from this article abstract). Now, from pressure vessel engineering, the hoop stress in a spherical shell is [math]\sigma = \frac{p d}{\mathbf{4} t}[/math], where [math]p[/math] is the applied pressure. This source gives a value for the tensile stress of egg shells as [math]\sigma_{\mathrm{max}}[/math] = 15.2 MPa. Assuming further the eggshell has similar strength in compression, and neglecting buckling, this gives [math]p_{\mathrm{max}}[/math] = 0.36 MPa or 3.6 bar. Would correspond roughly to the water pressure at a depth of 36 meters. However, presence of white & yolk will likely strengthen egg. A complicated question! (Edit: errors corrected! ) Edited May 5, 2011 by baxtrom Link to comment Share on other sites More sharing options...
Moontanman Posted May 5, 2011 Share Posted May 5, 2011 A boiled egg floats, but a fresh egg sinks. So you can go at sea and sink a fresh egg to make your experiment. Unless you want pressure by air and not by water. It is supposed impossible to break an egg by pressing in the palm of a hand. Be careful doing the experiment. NO IT'S NOT! Wipes egg yolk off shirt... Link to comment Share on other sites More sharing options...
michel123456 Posted May 5, 2011 Share Posted May 5, 2011 NO IT'S NOT! Wipes egg yolk off shirt... So you made the experiment! Link to comment Share on other sites More sharing options...
Hal. Posted May 14, 2011 Author Share Posted May 14, 2011 There was a demonstration on television a few months ago and it was about the impact energy that was absorbed by newly invented materials . An egg was dropped from a height , which was 4/5 metres at the time . It landed with it's longest axis vertical and this new super impact energy absorbing sample of material , covering part of the landing area , distributed the impact loads and the egg stood there , structurally fine . The demonstration was Chinese and the material was like plasticine , but I don't know if tricks were used . If it was all true , then the egg survived a 4/5 metre drop and impact . It was a short demonstration on a news channel and I haven't seen anything of this type of material since then . Link to comment Share on other sites More sharing options...
Hal. Posted June 27, 2011 Author Share Posted June 27, 2011 Here is a short demonstration which is about 10MB in data . Link to comment Share on other sites More sharing options...
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