How to make a Naked Egg
A “naked egg” is an egg that has no shell. Let me say that again, an egg with no shell. This is not something you normally run across and even when I show a naked egg to someone they often just don’t get the idea that the shell is gone – yet the egg stays intact. You might want to check out the anatomy of an egg to get an idea what we are dealing with.
The shell of an egg (typically a chicken egg) is made up of primarily calcium carbonate. If you soak this egg shell in vinegar (which is about 4% acetic acid), you start a chemical reaction that dissolves the calcium carbonate shell. The acetic acid reacts with the calcium carbonate in the egg shell and releases carbon dioxide gas that you see as bubbles on the shell.
CaCO3 (s) + 2 HC2H3O2 (aq) → Ca(C2H3O2)2 (aq) + H2O (l) + CO2 (g)
The egg insides remain intact and are held together by the two fragile membranes just inside the shell.
Here’s what you need
Let’s get to the fun stuff. In order to make a Naked Egg you will need the following items:
- Vinegar (at least 16 ounces)
- A couple of glasses or cups
- Raw eggs
The process is really very simple. Carefully place the egg in a cup and fill the cup with vinegar so that the egg is completely covered. Don’t worry if the egg floats a bit. Just get enough vinegar in the cup to mostly cover the egg.
An egg soaking in vinegar with part of it’s shell dissolved.
Now the hard part – you will have to wait as the acetic acid in the vinegar begins to react with the calcium in the egg shell. In just a short while, you should see some bubbles appearing on the outside of the egg. These are bubbles of carbon dioxide gas from the reaction. It can take 12-24 hours before a good portion of the shell is removed. A good sign of progress is a white frothy scummy layer on the top of the surface of the vinegar.
After a day of soaking you can carefully remove the egg from the vinegar. I would suggest pouring the liquid into another cup and catching the egg in your hand. Using a spoon to fish the egg out might seem like a good idea, but I’ve seen a few eggs break or get damaged when using a spoon to remove them.
At this point you may be able to literally rub the shell off the egg with your fingers. It will rub off as a white powdery substance. Give it try, just be very careful, you don’t want to break the egg, it’s getting more fragile as the shell is slowly dissolved. Depending on your particular egg, you may already have a naked egg. However, I would suggest you fill a cup with fresh vinegar and soak the egg for at least one more day.
After two days of soaking you should have a pretty cool Naked Egg. Notice that the egg is a bit bigger than when you first started. This is because some of the vinegar (and some of the water in the vinegar) has moved through the membranes to the inside of the egg. The membranes are semi-permeable and allow water to move through them. This is called osmosis.
Fun things to do with your naked eggs
Naked eggs are cool, but experimenting with them is even cooler. You have probably already noticed that your naked egg is kind of rubbery. How far above the table can you drop your egg and have it survive by bouncing? I would suggest you start at one inch, then try two inches, and so on. Keep in mind that eventually this is going to get messy when it the membrane breaks. You might want to do this experiment outside.
If you want to see your egg get really big, simply put it in a cup filled with water. The makeup of the inside of the egg is around 90% water. If you put the egg in a cup of (100%) water, the water will begin to move inside the egg through the membrane to equalize the amount of water inside and outside of the egg membrane. This process of water moving through a membrane is called osmosis. Osmosis equalizes – or makes the concentration of water on both sides of the egg membrane the same. This means the egg will swell as the water moves inside and get larger.
You can even color the inside of your egg if you soak it in some water with food coloring. This is a nice way to verify that the water in the cup is really moving through the egg membrane and not just coloring the outside.
A naked egg that was soaked in corn syrup for a few days. Much of the water inside the egg has moved out through the membrane.
Shrink your Egg
Now that you know about osmosis, you might ask “can I make my egg shrink” or shrivel up? Of course, you just need a liquid that has only a little bit of water. A common substance you may have at home that fits this requirement is corn syrup.
Slip your Naked Egg into a cup filled with corn syrup and let it sit for a day, or two, or more and you will begin to see your egg begin to shrink and look sort of baggy. Corn syrup has very little water content. Once inside the syrup, the water inside the egg begins to move across the semi-permeable egg membrane to equalize the water concentration. Again, that’s osmosis at work. If you leave your egg in the syrup long enough it will begin to look something like a huge raisin – with of course a yoke inside.
If you get tired of the shriveled egg look, you can reverse the process by just dunking the egg back in a cup of water. The water will once again move across the membrane and fill the egg with water again.
A big thank you to one of our visitors who grabbed a great photo of what happens when you soak a naked egg in corn syrup for a few days. I might call it a “dehydrated naked egg.” And side-by-side is a brilliant red naked egg soaked in red food coloring. Thank you Evers Ding for permission to use your photo and check out the rest of Evers egg photos on his blog.
Can I eat the Naked Egg?
Several visitors have posed the question, “Can I eat my naked egg?” I would NOT recommend eating a naked egg prepared this way. Keep in mind you created your egg by soaking a raw egg in vinegar sitting at room temperature for a few days. That is not how to treat eggs you are going to eat! Even if you stored the egg in the refrigerator, I still would not recommend eating the raw egg. Some have asked if you could store the egg in the fridge, then cook it and eat it. Well, I suppose you could, but given the amount of vinegar that probably moved past the membrane into the egg, it’s most likely not going to taste all that great. Instead of eating your naked egg, just experiment with it.
A dehydrated naked egg side-by-side with a brilliant red naked egg soaked in red food coloring.
Look, if you are really interested in creating a Pickled Egg that you can eat, check out some of the recipes from the National Center for Home Food Preservation and for more information about safe egg handling practices check out the Egg Safety Center.
Does it Smell?
A few of you asked if the eggs will start to have that rotten egg odor after a while. Well, I think it depends on how you store the egg. That rotten egg odor comes from hydrogen sulfide. Eggs contains sulfur because it is needed for the production of feathers in the chicken.
I have not noticed any bad odors with my naked eggs. After dissolving the shell in the vinegar, I keep the egg in a glass of water for up to a week and have not noticed any odor when the egg does accidentally break. It would be an interesting (and probably stinky) experiment to leave an egg out for a week or two in order to give it a chance to start to decompose. I would suspect that as the contents start to decompose, sulfide compounds will begin to form and it will start to smell really bad.
Science Fair Project Ideas
In terms of doing a science fair project here are a couple variables you might want to explore in more detail. Just a list of ideas to get you thinking. If you come up with other ideas let me know!
- Change in the weight of the egg. The egg will swell as water is passes through the membrane after the shell is removed. If you have a scale that measures to something like a tenth or hundredth of a gram, you may be able to measure the weight of the egg from start to finish and estimate how much water is absorbed. Perhaps your school has a scale that could be used for this? You could also soak the egg in corn syrup and chart the lost of water as it moves out of the egg. Could be messy as you would want to carefully wash off the syrup to make your weight measurements.
- Does temperature make a difference in how long it takes to remove all the shell? Eggs in vinegar in the fridge versus at room temperature vs simmering an egg in warm vinegar on the stove. Could be smelly.
- The effects of the concentration of the acetic acid. Typical vinegar is about 4-5% acetic acid. Many asian food markets carry Concentrated Vinegar
(~25% acetic acid). If you cant find the concentrated vinegar you could dilute the normal variety to various concentrations with water and see how that affects the time to remove all the shell. Do multiple eggs in order to collect more data points.
- Strength of the egg membrane. First make a dozen naked eggs so you can do multiple trials. Then test how much weight it will take to burst the membrane. This could be done by pressing ever increasing weight on the egg, or by dropping the eggs from successively higher heights until the membrane fails. This will probably be messy!
References
I’ve received many requests from students doing science fair projects related to the Naked Egg looking for further or deeper references. I have included some print references below. You can use the World Library Catalog to locate one of these items in a library near you!
- B. Z. Shakhashiri, Chemical Demonstrations: A Handbook for Teachers of Chemistry, Vol 3, p. 283-285, Wisconsin (1989).
- B. Cocanour and A. S. Bruce, J. College Sci. Teach. 15:127 (1985)
- V. L. Mullin, Chemistry Experiments for Children, Sterling Publishers: New York (1961).
- L. A. Ford, Chemical Magic, T. S. Denison and Co.: Minneapolis, Minnesota (1959).
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This is so totally cool! My kids and I are so doing this! Thanks!
if i’m not mistaken, vinegar is also use in the commercial food processing to “peel” hard cooked eggs in volume (the kind restaurants buy in gallon jars).
this is so cool im gona try this
I think,if you place the softend egg ,before the shell dissorves but is soft on the mouth of a heated glass soda bottle ,when the bottle cools it will suck the egg into the bottle.I think egg will get hard again inside the bottle.
you can also take another egg, cover it with flouride toothpaste, and put that egg in a container filled with vinegar, now let both eggs sit for the same time, and let kids see what happens. The flouride toothpaste will protect the eggshell, which is acting as the enamel of our teeth, and the vinegar is acting as all the nasty bacteria in our mouths. Your children will see why it’s important to brush their teeth everyday..this is a great science fair project..both of my children did this yrs ago, and both won!!!
I am a fifth grader and has chosen this project as my school science fair project.
I would like to know what sources you have used to come up with this idea.
Also I would like to know a little bit about you, please can you help me with this project?
Hi J-Dog,
Send me an email at carl@imaginationstationtoledo.org and we can talk in more detail about the naked egg experiment and your science fair project!
Carl
Carl Nelson
Chief Scientist
Imagination Station
I love science! Thanks for sharing!
ares had not cracked yet but its getting ready to so this is so exitting for us….
from
elie
pritty cool it look so amazing
this thing was so cool i dropped it from 6 inches on different surfaces and it never popped on the wood i used concrete and my asphalt road!
oh hi pliz help do u think it would be a good science fair questions and project?
I always thought the refrigerating eggs thing was just a refrigerator marketing ploy, although it probably depends on your climate. In a temperate country like the UK they will last for weeks just left in their cartons somewhere cool and dry.
I have cats and I was wondering so that they don’t get in it and play with the egg and break it can I store it in the refrigerator while the shell dissolves will it affect anything?!? I need an answer ASAP!! Thx
Will putting the food coloring in the vinegar or the vinegar itself change the taste of the egg or would the egg just not be edible anyway? I’m thinking about doing Dr. Seuss’ Green Eggs and Ham and just wondering if this would work.
Do you put the food coloring in with the corn syrup to make it that color?
Hi Samsang,
You can certainly put the food coloring in the vinegar and get a color change in your egg. I just wouldn’t suggest eating the egg that has been sitting out for several days just to be safe.
Carl
Hi,
You can do this experiment in the refrigerator. It may take longer to fully dissolve the egg shell since most chemical reactions slow down as the temperature is reduced. Give it a try and let me know how it works.
Carl
I put the naked egg in a cup of water with a lot of food coloring to get it that deep shade. When you put the egg in the corn syrup you are trying to remove as much water as possible, so it would slow down the extraction of the water if you put food coloring in the corn syrup.
Carl
Just to be on the safe side, I would not suggest to anyone that eating eggs that have been stored in a vinegar solution at room temperature is a good thing.
Carl
Sure!
You could explore all sorts of variables. For instance, the concentration of the vinegar, the temperature of the solutions (try it in the fridge), etc. If you have a sensitive food scale you could try to measure the weight change of the egg over time as it swells or shrinks (in corn syrup).
Carl
Thank you for this information. I am adding it to my sensory training for our teacher assist preparation program my agency is sponsoring. They are going to love this! I may have to add it to my SUTQ training also
I’m doing a science fair project similar to this, but I’m trying to test what type of liquid would dissolve the shell the fastest. Is vinegar the only liquid (liquids that are edible) that would dissolve the eggshell?
What happens if you soak the egg in vinegar for about 2-3 days and you don’t change the vinegar water…what will happen?
Well, that is a great idea for an experiment! Remember that the acid in the vinegar is reacting with the calcium in the egg shell. When enough (or all) of the acid is used up, the shell will stop being dissolved. I’ve always been in a hurry to remove the shell, so I’ve never just let it sit in the original vinegar for to long. Give it a try and let us know what happens!
Carl
Well, it’s the acetic acid in the vinegar that is doing the work of removing the shell by reacting with the calcium carbonate in the shell. If you can find other edible liquids that have acetic acid in them they should work to some degree as well. Other acidic solutions such as sodas that contain acids such as citric acid or phosphoric acid may work as well. Sounds like a good science fair project.
Carl
This project seems awesome but I’m trying now and it takes really long.is there any way to speed up the process?
Hi Anastasiya,
It should only take two days to remove the shell with ordinary (5%) vinegar. If you want to speed things up you could use concentrated (25%) vinegar. You can typically find it at an Asian market. If you are very careful, you could also speed up the process a little by gently rubbing the egg to help remove some of the shell as it sits in the vinegar.
Carl
Carl- Ali and I made the naked egg. My questions are
1. How long will it set for, before it starts to smell or anything else?
2. Should we freeze it or put it in the fridge.
3. How long does it have to sit in water before it starts to get bigger?
We keep our naked eggs in a cup of water in the fridge. I’ve never tried freezing a naked egg, might be an interesting experiment. We have never had an egg that smelled bad. The egg should start to swell as soon as its put in the water. It may take a day or so before you will begin to see a difference.
I’ve tried to do this 3 times now and every time it get a pin size hole in it I was wondering if there’s a way to fix it before its completely broken? and witch vinegar works best? I’ve been trying it with apple cider vinegar and I almost have it but then when I lightly rub off the last of the shell it pops plz help.
Can you put a glow stick in it
I haven’t tried it yet, but another liquid that may dissolve the egg shell is Coke or Pepsi. They will eat away at a tooth. We tried this in elementary school.
we started our egg after school today, my 5 year is very curious as to what will happen. Please if you have any other cool science experiments that are safe for a his age please let me know. Thanks and I am looking forward to see my egg change!
Would white vinegar work?????
Yes, white vinegar will work.
Carl
Hi Rebecca,
I would suggest you just leave the egg in the vinegar and don’t try to rub it. Sometimes that works, but you have to be really careful. Try swapping out the vinegar every day for a few days and you should have no problems with the egg bursting.
Carl
hello i am a seventh grader and i might do this for my science project in two weeks hope i can do it in time !!
do you think i should do this for my science project in two weeks i am a seenth grader not sure so you tell me if i should or not?
Hi Sandylily9,
I think you should give this experiment a try. Seems like you still have time to get things done if you start now. Get some vinegar and soak some eggs now, just to try things out. You should still have time to do it again (it only takes a few days) and apply some questions to the process. If you need more help let me know!
Carl
Cant wait to try this with the kids. Wondering what would happen with different things like glow in the dark chemical or Black light eggs! How could I remake the shell to trick someone….dried glue?
I am a 5th grader and doing this experiment. My egg began to spin and move around in the vinegar about 45 min after I put it in the vinegar. Can you tell me what caused this to happen?
how high can the egg bounce just give me a estimate please really need one?!
Did you cover your cups or have you ever used jars and sealed them?
Hmmm… Can I put several eggs in a larger container?
Yes, you can put multiple eggs in a large container.
We generally don’t cover the containers when doing this activity. You could try this and see if it makes a difference. There is some carbon dioxide gas released during the reaction, but I doubt it would build up enough pressure to burst the container. Give it a try both ways and see if you get different results.
Well, it could be a few inches or more. It really depends on the individual egg membrane.
Hummm, that’s interesting. I wonder if it was the build up of carbon dioxide bubbles on the side of the egg causing it to move? As the egg moved some of the bubbles could have popped and then bubbles on the other side of the egg could have started it moving again.
what do u do the egg when u r done