Introduction: Century Eggs

Picture of Century Eggs

Whether you call them century eggs, hundred-year eggs, millennium eggs or whatever, these outlandish ova are a Chinese delicacy dating back centuries to the Ming Dynasty. The boastful name suggests these eggs take forever to make, this is a misnomer. Century eggs take about 4-5 weeks to make, a few minutes to work up the courage to open, and a few seconds to eat.

Traditionally century eggs were made by preserving chicken or duck eggs in a mixture of salt, lime and ash, then wrapping in rice husks for several weeks. During this time the pH of the egg raises transforming the egg, the chemical process breaks down some of the proteins and fats into smaller, more complex flavours. After curing the yolk of the egg turns a dark green and has a creamy consistency, while the white turns amber and is gelatinous. 

I chose a more modern method to achieve the same results: a salt and lye pickling solution, and encasing in modelling clay. After about a month my eggs were ready, and I'm happy to say they turned out perfectly!

Want to make your own? Of course you do! 
Enough talk, let's make some eggs!

Step 1: Supplies + Materials

Picture of Supplies + Materials

  • 100% lye/caustic soda (NaOH - sodium hydroxide)*
  • salt (NaCl - sodium cloride)
  • chicken egg (duck or quail egg)

* Technically lye is a corrosive, not poison. Though, it' can be labelled as either. It's incredibly dangerous to handle and can cause severe burns with contact to skin, there's also an inhalation risk. Use gloves and a respirator.
There's plenty of other foods that are made/prepared with lye, but use caution and common sense.
Always use pure, 100% lye (sodium hydroxide).

Step 2: Prepare Pickling Solution

Picture of Prepare Pickling Solution
Start by making the pickling solution, here's the basic breakdown:
  • 1L  - Water
  • 42g - Sodium hydroxide(NaOH)   (lye)
  • 72g - Sodium chloride(NaCl)   (salt)
On a scale weigh out the lye and salt. Over low heat dissolve the salt and lye completely in water. Bring the solution to a boil and allow it to cool down before use.

Place raw eggs into glass jar and pour the cooled pickling solution over eggs. Ensure all eggs are completely submerged. 

Step 3: Store

Picture of Store

I wrote the date of submerging these eggs on my label, as well as the expected dates for encasing in clay, and eventual consumption. Label jar and store in a safe place, like the corner of your desk, so all your coworkers can gawk in disgust (or silent admiration). I also added a warning so my coworkers wouldn't mess with the jar while the eggs were pickling.

Leave eggs at 15-20°C (60-70°F) for about 10 days. Keep an eye on them to ensure they don't pop up above the solution and stay submerged.

Step 4: Remove From Brine

Picture of Remove From Brine

After about 10 days it's time to remove the eggs. Carefully pour out brine and pick out eggs, rinse with water then towel dry. The shells should still be hard.

You should be able to see some discolouration through the shells. 

Step 5: Encase

Picture of Encase

Traditionally century eggs were rolled in mud then wrapped in rice husks and buried for a few more weeks. In this modern version I simply wrapped the eggs in several layers of clear plastic wrap then encased in modeling clay. This inhibits oxygen from reaching the eggs while they cure.

Be careful when encasing in clay as not to break the eggs. After wrapping I put all the eggs into a resealable bag and left for another 2 weeks. 

Step 6: Crack Open

Picture of Crack Open

After about a month from the when the eggs were first put into the brine solution it's time to open them up. Carefully remove the clay encasement and the plastic wrap, then tap the egg to break the shell and gently peel away. The eggs should be completely transformed!

The whites of the eggs will now be a jelly-like translucent amber colour and the yolks a very dark green and with a texture much like a hard boiled egg. Take a look at picture 2 in this step to see the different consistency between the yolk and white in my egg-xperiment.

Step 7: Serve!

Picture of Serve!

Century eggs are typically served mashed up in soupy rice. I made a steamy bowl and served it to my friends.

The taste was...interesting. The appearance is deceiving and almost put me off eating it altogether, but once I ate some it wasn't that bad. It tasted kind of like a hard boiled egg, only with a more complex flavour and a slightly mineral/metallic taste. I'm happy I tried this and think I would probably eat it again. You know, sometime later (much, much later).

Did you make your own version of century eggs? Post a picture in the comments below and earn a free 3-month Pro Membership to Instructables!


KenH61 (author)2016-03-15

Please dont eat anything that required drain cleaner to make. If this isnt illegal it should be.

mikeasaurus (author)KenH612016-03-16

You need to use 100% pure lye, anything mixed with chemicals is unsafe.

Lye has loads of applications with food:

Tommo020788 (author)mikeasaurus2017-07-03

Please change the image you have displayed for ingredients.
Yodu are suggesting for people to use drain cleaner for this by using that image, and that is not safe.
100% lye doesnt mean its safe to use in food apications.
You need "FOOD GRADE" lye. Its even listed in the wiki page you linked to.

JustinI8 (author)mikeasaurus2016-09-11

Hey, i started a batch yesterday and one of the eggs has broken in the jar (i was tipping it round to ensure even coating of solution). Are the other eggs safe? Will the lye kill off all the possible contaminants from the raw egg that is now in the solution?

mikeasaurus (author)JustinI82016-09-11

I wouldn't eat the broken egg, but the others should be fine.

mewat (author)KenH612016-03-25

It should be illegal that you are allowed to post such rubbish. These are eaten since ancient times. Shame on you!

anthonymaw (author)2017-06-11

Why didn't you just go down to your local Chinatown restaurant and just order a dish of the real thing made by Chinese? Or in the USA you can probably just buy "Century Egg" on Amazon these days. Cheers!

cbaumle (author)anthonymaw2017-06-28

Where's the fun in that?

Paulguad (author)2017-03-24

I have been making -- and eating -- these for years. After the brine I seal each one in a little bag with my vacuum machine. Works perfectly well

TaiF3 (author)2017-03-23

You do not need to heat the solution... in fact do NOT pour lye into heated solution because they will react vigorously. The salts will dissolve in cold water (lye will warm it up a bit).

Also the eggs will float since you just made the solution denser by adding salt and lye to it..

phettsack (author)2012-01-13

As those eggs aren't cooked, I am courious about germs.
Whats about bacteria like salmonella? Are they gone?

TaiF3 (author)phettsack2017-03-23

Century egg is pickled, meaning they are soaked in a strong brine solution that kills bacteria. I do not think bacteria can live in an extremely high ph environment, not to mention how salty it is.

I have seen century egg sold in stores here in the states refrigerated and I do not think it's necessary since those eggs are preserved, so it will not spoil unless the shell broke.

It's a bit like pickled eggs.

I eat UNREFRIGERATED, RAW eggs all the time without incident. you can store them on the counter at room temp for at least two weeks. even recommends it. what's more, salmonella is not a death sentence. eat farm fresh, free range, organic, anti biotic free and pesticide free as much as possible.

you feel better now? the guy was simply asking a question, not questioning your beliefs.

crwydryny (author)phettsack2013-08-15

the curing process kills the microbes that would otherwise spoil the egg, that's why the egg can last as the name suggests a hundred years and still be edible. as long as you don't mind something that smells of rotten eggs, it takes a lot to attempt to eat one and is an aquired taste (not to mention texture) so they are safe to eat, but if they'll stay down, that depends on the person eating them. they were invented as a way to preserve eggs through the winter months back when there were no green houses pumping out fresh fruit all year round or imports from africa and south america in the corner shop less than a week after being picked. so it was an emergency solution that evolved into a delacacy

abbyr (author)phettsack2012-02-09

who cares about poison

superbird (author)phettsack2012-01-13

I am not sure about the the germs issues, but I ate it from child till now, not cooked. But will cook with pork Congee most.

YutaiL (author)2016-10-06

Hi Mike, great tutorial. Just wondering about the last step. If the goal is to keep oxygen out, can I just vacuum seal the eggs instead of the cling wrap and clay? Thanks!

mikeasaurus (author)YutaiL2016-10-06

Probably, but if your bags don't seal or are punctured you risk spoiling your eggs. If you try it I'd love to see your results!

AnthonyP131 (author)2016-09-14

In my opinion, the best way to have pidan is either:

crumbled in porridge(congee) with lean pork,

or sliced and laid on a deep plate with big slices of silken tofu and convered in soysauce, green onions, and a hint of vinegar.

I am so happy to have found this post, as I just got a massive craving for these delicious eggs, which I have not had since I moved back to the States from China earlier this year.

Thank you soooooooo much for this delightfully simple recipe! Cannot wait to start a batch of these tomorrow!

KenW5 (author)2016-07-18

Heck, there are plenty of foods that are prepared with lye, such as the wheat in white toast. To all the haters: embrace diversity or at least tolerate it.

zdoan (author)2016-07-07

Here's some informational video.

Bloom. Also known as the cuticle, bloom is the natural coating or covering on the eggshell that seals the eggshell pores. The bloom helps to prevent bacteria from getting inside the shell and reduces moisture loss from the egg. In nature, the bloomdries and flakes off.

ossum (author)2016-04-01

I just ate a whole bunch of these last night for the first time,so I had to google them this morning (that is a pretty standard routine for me when eating in Beijiing). I should have known that one of the first results would be an Instructable, not only explaining what they are, but how to make them too! Great job Mike.

P.S. I received them on a plate of chilli-sauce, covered in chillis

tonysuffolk (author)2016-03-16

I make "pi dan" using this method, except I leave them for 14 days. I first thoroughly scrub the duck eggs to remove the film which sometimes forms on the shell. It's important that the pores of the eggs are not blocked, otherwise the caustic brine solution cannot penetrate properly. When dried, I paint the eggs with PVA glue to seal out the air and then wrap them in "cling film". They are usually ready to eat in a further 2 weeks. I get the odd failure. I love them with tofu, sweet sticky soy sauce and a sprinkling of pork powder (if I can get it at my local Asian food shop). Dried onion flakes also give a pleasant crunchy texture. My wife, who is Taiwanese, and I don't need to share them with friends. One look and they usually pull a face! All the more for us!

mikeasaurus (author)tonysuffolk2016-03-16

You're either in the centry egg club, or wonder why people are. There's no middle ground.

LarryL33 (author)2016-02-25

Thank you so much, I made about 2 dozen duck eggs and it turned out pretty good except that the egg white somehow remained mostly liquid even after over a month of being covered in clay. I followed each step, what did I miss? :(

mikeasaurus (author)LarryL332016-02-26

Were they soaked in the lye solution long enough? Perhaps they were'nt completely sealed from air afterwards.

There's definitely some experimentation to achieve the best results for your eggs. I'd love to know more of your results, please share!

acd111 (author)2016-01-17

I just started the process of making this, and I measured the lye and salt very carefully (within 1g of accuracy) but my eggs seem to be cracking open within 12 hours of submerging in brine. At least 3, maybe 4, out of a dozen chicken eggs have cracked a bit, but the membranes are mostly intact. My guess is due to osmosis, or maybe the egg shells are a bit thin.

XuanV1 made it! (author)2015-11-01

I have successfully made it today, followed exactly your instructions and steps. I cracked the egg and astonished with the transformation of the egg. Can't explain how happy I was. Thank you very much for your wonderful egg-xperiment!

mikeasaurus (author)XuanV12015-11-02

Glad it worked out for you! Your egg looks awesome, how did you enjoy the taste?

Thanks for sharing a picture, enjoy the Pro Membership!

XuanV1 (author)mikeasaurus2015-11-02

Dear author, thank you very much for the member you offered me. I sure will enjoy it very much. The taste is a little bitter on the amber part, muddy part tastes good, and it has the smell of clay, is it strange ?

jacobevolved (author)2014-05-03

I wonder if sodium silicate could be used instead of the clay....

painrelief (author)jacobevolved2015-07-16

Sodium silicate found in furnace cement should probably not be used. In my experience, it dries up really hard and is tough to remove. In the past, I've seen these eggs rolled up in a coat of (wood) ash. I assumed that it was also used to raise the pH

RayL4 (author)2015-03-01

Alright! I'm gonna start the process tonight! Thanks so much for this write-up! How in the world did you even get the asian century egg sensei's to give up their secrets??

byesuah (author)2014-04-15

i had this in China a few years ago. everyone was freaked out by this and didn't try , but I didn't think it was bad. I'm interested to try it on my own. :-)

rtiamson (author)2014-02-20

if i will use lye many cups i need?

mikeasaurus (author)rtiamson2014-02-20

See Step 2

GnomeToys (author)2013-06-11

"Drain opener" style sodium hydroxide may contain heavy metals. You should really, really, find food grade lye online instead.

FlatLinerMEDIC (author)2012-07-25

They taste like urine- andrew zimmerman - think thats how you spell it

desmondtheredx (author)2012-01-29

In china there are eggs like this that are made really quickly but were kinda dangerous to eat (due to chemicals). but how does NaOH and NaCl pickle the egg?

BioT (author)2012-01-18

I'm very concerned about the number of people I've seen referring to these as being made with "drain cleaner" (or some variation of that statement).

Lye itself is corrosive but if it's used in the right amounts and carefully it is perfectly safe for preparing food (it is such a high pH base that it kills bacteria, similar to pickling with vinegar -- a low pH acid)

But most dry "Drain Cleaner" usually contains bits of aluminum. The lye (NaOH), when it becomes liquid in water, reacts with the aluminum and creates:
- (A) bubbles,
- (B) heat... and lots of it. Enough to cause heat burns (I've seen it melt plastic bottles!). and then
- (C) the bubbles are likely pure Hydrogen -- thus, flammable or explosive!!

As a Biology teacher (hence the "BioT" name) I made these in class but I also had to teach some Chemistry. I used to use this Lye + Water + Aluminum to show that it would make hydrogen.  I collected the gas in a balloon in class. Then to prove it was Hydrogen I'd have someone ignite the balloon with a match at the end of a yard/meter stick. BOOM!   

SO, I'M JUST SAYIN' -- #1. Don't use Draino, drain cleaner, etc... use plain old Lye (NaOH), and #2. Don't use the Lye if it might come in contact with Aluminum... the catalyst that causes it to release Hydrogen gas!

Other than that, have fun and enjoy your eggs. They're good. As I said, we made these in my Biology class, too. But only a couple students were "gutsy" enough to try them. ;-)

chiao (author)2012-01-14

Yes! I love these! Unfortunately, my wife just bought some, so she won't let me make them right now. I like to eat them sliced with soft tofu and thick soy sauce. Mmm! Now I just need to learn to make my own rice wine and tofu...

zhenpenthaye (author)2012-01-12

Often served in Chinese restaurants in Thailand - in Thai language referred to as "horse urine eggs" - go figure!

(It's the ammonia.)

eyewalk (author)zhenpenthaye2012-01-13

Thanks - always wondered how they made them!
Here in thailand, these "kai yeow maa" (horse piss eggs) are used in a few dishes.
I would say the best is "kai yeow maa gaprow grop" which translates to horse piss eggs with crispy basil.
Simple recipe:
1. Heat oil in wok and flash fry basil leaves until crispy. Here we use holy basil which is slightly spicy. The fried basil loses most of its flavour though so any basil will probably do - it's for colour and texture anyway!

2. Quarter horse piss eggs and deep fry until outsides are a medium brown. Drain or put on paper to soak up excess oil.

3. Make a sauce using soy sauce, vinegar, sugar, chilis (optional but gooooood!), then corn or tapioca starch in water to thicken the sauce. Heat and simmer to thicken the sauce. Add basil leaves (lots) in the last 30 seconds of cooking.

Put the eggs on a plate, pour sauce over them, then sprinkle the fried leaves over top.

ksexton1 (author)2012-01-13

Everyone thinking lye is artificial, lye is traditionally made by slowly leaching water through wood ash. The eggs might even be able to be considered an organic food. Powdered drain cleaner is lye+aluminum shavings+possibly color crystals, anti-clumping agents, fillers, etc.


try eating them steamed. it takes the "edge" off the taste. Also, great steam with egg and salted egg!

ChrisSWK (author)2012-01-12

I am Chinese from Malaysia and in my country, we eat this with pickled sliced ginger and its taste is awesomely great. However, do take caution as this egg is high in cholesterol. Won't want to have heartattack after taking it...

To have this in Fear Factor, eating it will be a piece of cake...

Great stuff in sharing the "Recipe"....

branhamr (author)2012-01-12


See comment by submark on Step 1 page.

PCBrewing (author)2012-01-12

Correct me if I am wrong, but I think you could use; Pickling Lime (Calcium Hydroxide) to increase the Ph and remain food safe.

hammer9876 (author)2012-01-12

There is got to be a good way to keep the eggs submerged since that seems to be important.

You don't mention your gloves. Is that to protect you from the brine or the eggs from contamination?

As for "Step 5 Encase" - plastic wrap, modeling clay, and a resealable bag? Gosh, what happens if you don't do this well? Do the eggs go bad? Please define "bad." :-)

Congrats on being Featured!

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