Egg in brine
I'm fascinated by old cookbooks that describe cooking techniques before food processing took over, which began to happen in the 1920s and then exploded after World War II.  I've mentioned my favorite, Miss E. Neil's cookbook, in this post on recipes.  She's writing at a time when there weren't many standard measuring devices, certainly no digital scales, no instant read thermometers.  A common instruction that fascinates me is to "make a brine strong enough to float an egg."  I've always wondered how much salt that would be.

So I asked my trusted culinary assistant, James, to weigh out three different weights of salt in the same amount of water to make a 5% brine, which is what I use as a standard brine for everything, whether for a chicken or to pickle vegetables or corn beef, a 10% brine which is a good strong brine, and a 15% brine, 75 grams of salt in 500 grams of water.

The above not-by-donna photograph is a little hard to make out, but the egg on the left, in the 10% brine is not floating while the egg in the 15% brine is.  15% brine is very strong, you'd have to use it judiciously. I'm glad I have a scale!

Also, I've always been curious about what happens when you brine an egg.  Can you preserve them this way?  I've heard you could.  Must they be cooked first, then brined? When I left both eggs in the 10% brine for a few days, they both evenutally floated.
Anyone know why this would be?  Anyone brine eggs before?  What's going on here?  I have to assume there's a reason people aren't soaking raw eggs in brine all over the place. I'll leave them in for a week and see what happens.


41 Wonderful responses to “Playing with Food: Eggs in Brine”

  • dan

    Micheal, I haven’t brined eggs but I have ‘smoked’ them in liquid smoke.

    My experience was that after a while (2/3 days)the eggshells softened, eventually becoming quite hard to handle.

    My assumption was that this was to do with the liquid (basically water) and not anything to do with the ‘smoke’ compounds (or chemicals) in the liquid smoke.

    On a tangent, I went diving once off Cyprus where a large auto ferry had been sunk. On the sea bed were 1000s of eggs that were still intact. Wonder what they would taste like 😉

  • brandon_w

    Salted Duck eggs are apparently cured in a brine. I had thought so and confirmed it on wikipedia.

    Here is a recipe for something similiar, Salty Eggs, which is according to the recipe the Thai way to do it:

    When I was in SouthEast Asia eggs prepared in this way were for sale at every market, along with the 100 year egg and a few other seemingly preserved types.

  • elsimom

    There’s a science experiment in which you put an egg in vinegar. Eventually the calcium carbonate in the shell is dissolved, leaving a sort of rubbery inner layer, with the yolk and white intact. The dissolution is the point of the experiment, but I don’t know if the resulting eggs are edible (safe OR tasty).

  • billb

    There are lots of semipermeable membranes in an egg. The strong brine draws out water via osmosis through these membranes. Since nothing is drawn in in any large quantity, the density of the egg drops. Once the egg is less dense than the brine, it floats.

  • Jason B.

    We raise chickens and use a float test in pure water to tell if the eggs are spoiled. I assume its do to a conversion of egg to gas as they rot. Please be careful if you use those eggs. Sulfur is not a pretty smell. Hopefully the salt keeps bacteria at bay.

  • b

    MMmmmmm. I’ve brined chicken eggs in attempt to make Chinese/Filipino salty eggs. Very, very salty eggs. First, I boiled water and kept adding salt by the spoonfuls until there is a brief crystallization on the surface of the water. It was about 1 cup salt to 4 cups of water. Then I added the cooled brined to the *raw* eggs and let sit for anywhere between 2-4 weeks, depending on your taste. I prefer to let it sit for slightly more than 2 weeks, which is not even as salty as the ones sold in Asian markets. Obviously, the longer you let it sit, the saltier it gets. Once I got my desired saltiness, I boiled the eggs in the usual manner and then eat it. This is Asian-style salted eggs, so it’s an acquired taste for that much salt. I’m not sure what Western-style brined eggs are like.

  • chris bellamy

    If you left the eggs floating in an *uncovered* 10% brine for a few days, I would guess the reason they floated is because some of the water in the brine evaporated, increasing its density.

  • Toke-Dawg

    Hey Michael,

    The floating is a matter of density. The less dense material will float atop the denser one. If you add enough salt (dense) to water (less dense), it raises the density so that an egg (at a set density somewhere between salt and water) will float. That explains why it will float in a 15% and not a 10% brine.

    The change in the floating capability of the egg in the 10% brine is a matter of osmosis. Osmosis is a type of diffusion that involves an object with a semi-permeable membrane, a shell in the case of the egg. The shell, being semi-permeable, allows for water to pass through, but not salt. By the laws of probability and entropy, diffusion works in a way that favors a solution that has a uniform osmolarity (basically meaning water to stuff ratio). This means that the water inside the egg white (water is pretty abundant in the egg white together with the albumin protein) will pass through the shell to try to equalize the osmolarity on each side. Since the egg loses water, its overall density becomes lower, meaning that eventually, when it loses enough water to make its density less than the brine, it will float. Additionally, don’t be surprised in a small-scale experiment if your 10% brine becomes 9% or 8% due to the water that it “takes” from the albumin in the egg.

    Hope that helps.

  • billb

    I like Chris’ answer, too. It might be fun to try an experiment with plastic wrap over the top of your container.

  • Andy Coan

    “Make a brine strong enough to float an egg” is brilliant technique. No measure, no fuss, just salt and water. That’s pretty cool. What else floats/doesn’t float that could be used for meaningful measurements?

  • Andy Coan

    I must say my first instinct of the suddenly-floating egg–half joking–was in line with Jason B’s post…I would do the egg-cracking part of this experiment outside. 🙂

  • Sam Engelhardt

    What about pickled eggs? They’re all over the south. Would you have to use vinegar or could you put them into a brine with some vegetable that would add flavor and give the sugars to break down into vinegar? For those I know you cook the egg first.

  • Russ

    Not sure what else might be im- or semi-permeable in the natural world, but for someone who makes a lot of brines it might be interesting to make a set of floats for various percentages.

  • John Bowers

    I have soaked hard boiled eggs in apple-cider vin overnight. As was mentioned in a previous comment, the calcium carbonate breaks down and the egg (shell and all) becomes squishy and bouncy. I eventually ate some of this egg and found it pretty gross but I imagine the right balance of vinegar, salt and maybe other aromatics may yield some interesting flavors… Particularly within Asian flavor profiles.

  • kayenne

    i concur with the above posts on asian salted duck eggs. duck eggs are used due to the higher fat content. when there’s oil in the dark yolk after it’s been cooked and cracked open, that’s the sign of quality.

    a supersaturated salt solution should cover the raw duck eggs and left to brine for 21-28 days for best quality. a plate or a bag filled with water is usually put on top to ensure the eggs are completely submerged. then boil like you would for hard-boiled eggs. allow to cool. this can be refrigerated for a looooong time.

    some sellers wanting a quicker turn over let the eggs brine for a shorter period of time, but the eggs tend to go bad easily and doesn’t taste as good.

    chicken eggs are not normally used. doesn’t taste as good – too low fat content.

    now, you made me crave for some with a steaming bowl of congee.

    preserved sliced green mangoes and peeled santol (aka wild mangosteen) is preserved similarly in a salt-sugar solution.

  • kayenne

    if i recall what my science teacher told me, the eggs float as osmosis takes place. salt is drawn into the egg, while water is drawn out to equalize the pressure or density.

    also, if i recall correctly, a not-so-fresh egg will float in water due to evaporation. the air pocket at the bottom of the eggs gets bigger due to the loss of moisture. a few days in salty water speeds this up.

  • chris bellamy

    @toke-dawg and @kayenne – I think that if osmosis were the only factor at work, that:

    a. Osmosis through an eggshell, if it happens at all, would be much slower than evaporation of the water in the brine. The classic osmosis experiment with an egg involves dissolving the eggshell with vinegar to allow osmosis on the membrane inside the shell without the shell in the way.

    b. Osmosis with water going from inside the egg to outside the egg would also decrease the density of the brine, not just the density of the egg.

  • mike

    @AndyCoan: “What else floats/doesn’t float that could be used for meaningful measurements?”

    Wood? Very small rocks? A duck!

  • cory barrett

    Do you think that over time the egg will sink? the shell has pores, and the salt may pull water from the white changing the salinity level in the brine, and making the egg less dense… i don’t know.

  • craigkite

    I was just waiting for the Monty Python responses to come in. The egg is a witch!! But it made batter.

  • ruhlman

    cory, i think it will ultimately achieve equilibrium with the water due to osmosis.

    Delighted people have been able to bring Monty Python into this discussion!

  • Rhonda


    Dear Mother of God: it is floating due to salt vs water content.

    My experience with brining eggs is cultural.

    I am Irish/German (no, I do not know how that happened) but yes, you probably could brine an egg this way.

    The question is WHY?

    You are part Ruhlman (German). Make peace with your salt and vinegar and all will be well.

    I have a fantastic cookbook that was partly assembled by my Great Grandmother. It calls for Vinegar in Tomato soup. Made during the war.

    Fascinating. Will copy and send when I can.

  • Rhonda

    To Clarify:

    The food in my Great Grandmother’s Church assembled cookbook was absolute Shiite.

    What is fascinating is the ingredients they had available to them at the time (rations), and how they used them.

  • Cali

    My grandmother used to make dill pickles using the egg floating brine method. As I recall, once they were done stinking and were canned they tasted darned good. I remember going to sleep at night in the summer with boxes of canning jars under my bed going pop, pop, pop, at random intervals. Thanks for the nice memory.

  • luis

    Why brine an egg in the first place?. This obssesion with oversalting everything is another indication you like to push the envelope. It is very confusing Michael. One minute you are the picture of healthy organic local grown groceries and the next you are the wacko over salt over sugar and over fat fiend the comercial world rotates around. Very confusing indeed.

  • Chip

    Andy Coan asked, “What else floats/doesn’t float that could be used for meaningful measurements?” When I need a very specific measure of butter or shortening, I float it in water to measure by displacement. If I need 1/3 cup butter, I measure 2/3 cup water and add butter until the water rises to 1 cup. Done.

  • Jennifer

    I’m an elementary school counselor and I do an activity using eggs and brine with students. The egg is sad and covered with negative emotions (the water) and the students make positive comments (and I add salt for each comment) and eventually those comments buoy the egg and make it float. I use about 2 or 3 cups of water and in the course of 15 minutes we end up adding about a third of a Morton Salt canister to the water, but the egg floats by the end.

    Schools also use the egg in vinegar experiment to show what happens when you don’t brush your teeth–the enamel gets soft and doesn’t protect the teeth as well.

    We obviously don’t eat any of these eggs–it is just to give a visual to the lessons.

  • Jw

    I have done the salted egg thing before (as a condiment in pho or laksa) and have often wondered if there is any way to get jalapeno flavor/heat in there as well as salt. Perhaps the brine would serve as a vehicle for the jalapeno?

  • chef gui

    Yep, you have smart readers, Ruhlman. Commenters before me talked about osmosis and evaporation, which are both responsible for the egg starting to float.

    And don’t take this personally, but we prefer photos by Donna. Put her to work!

  • mike

    All the osmosis stuff is way off. It’s simple buoyancy that is responsible for the egg floating. Things are more buoyant in saltier water. As Jennifer pointed out above, we did this in elementary school but as a science experiment (I actually entered almost exactly what you did above in a science fair).

  • Donna

    chef gui–I totally agree!
    Michael, why do you insist on taking such bad photos with your iPhone? I know you can do better—I think you might be doing it because you know how much it bothers me and I’ll be sure to lurk around looking for your kitchen experiments more and ask if you need me to shoot.

  • luis

    Donna, I love your work in still photos and ratio etc… no lack of talent there. Why haven’t you published some videos? I mean To me it seems if you can do stills… a video should be cheesee piecee…for you.

  • Donna

    To luis
    Video and still photography are 2 different disciplines completely–
    I have tried taking videos and the results were not good–and that’s due in large part to not having done them for 27 years–which is how long I’ve been doing stills.
    Are videos more desirable then stills for blogs?

  • Darren

    Donna, your photography is wonderful. As for video don’t sell yourself short. You might look into the Canon EOS 5D Mark II Digital camera. It has the ability to shoot HD video (with sound). And since it’s a SLR it wouldn’t be much different for you. Compose, focus, shoot!

  • pastrygirl

    Growing up Chinese, my father an actual chemist and chemistry teacher made the Chinese salted duck eggs a few posts have been talking about. He used duck eggs from the local farmers markets, boiled the water added the salt to a specific molarity and then put in the eggs. Of course he double checked the solution by seeing if the eggs floated- since the eggs did vary season to season. My mother would then use the eggs in a variety of Chinese dishes throughout the year. I have to say they were better than what I’ve bought in the stores- I just might have to look up his recipe and find a scale. The real question is finding good raw duck eggs at a farmer’s market.

  • matt_bazley

    I think this is a very interesting discussion. but the thing that has me quite amused is the fact that donna and her prowess with a camera has somehow managed to take over the conversation. you all do a very good job, but I thought we were talking eggs….just thought I’d throw my comments in the mix 🙂 keep up the good work

  • Robin Easterbrook

    Michael: About 20 years ago I first became interested in the subject of sausage making and meat curing. The book I picked up on this topic seemed to me to use a horrendous amount of salt in their cure. So one day when I was buying some sausage from a butcher whose work I very much enjoyed, I asked him what the proper amount of salt to use in a cure would be. His response was “enough to float an egg”. Just thought you’d like to know.