Picture of Giant Plaster Easter (Dinosaur) Egg
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These will blow the mind of a child on Easter morning and is a fun afternoon project.  I made these for a video I shot.  We needed large eggs that I could put a hand inside and break out of, and these worked nicely.  But I also found that they were fun to make, great decorations and kids love them.  Thanks to Tom Cline for showing me his Giant Plaster Egg 12 years ago.
WARNING, this is easy to do, but tough to master.  It will take several attempts.  Be patient and do this in an area you don't mind getting dirty.  The eggs tend to explode when you are making them, (nothing dangerous, but messy) and you will get plaster everywhere.

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Step 1: Materials

Picture of Materials
Plaster of Paris-one box.
Bag of 9" balloons-round (but really Egg Shaped) clear is best, or white  or yellow, easy to see through.
Empty bottles of water-1/2 liter.  Easy to crush.
Mixing cup, more than 1/2 liter.
Mixing stick
Exacto Knife or Razor Blade
Spray paint
Towels, drop cloth, (did I mention this is messy?)

Step 2: Mix your plaster

Picture of Mix your plaster
The mix should be a bit runny, like a thin milkshake, it should pour easily, like syrup.
This is important; too thin and the walls of the egg will be too thin, too thick and it won't spread around enough.  Too much water and it will take a very long time to harden.  All I can say is try and try again and know it won't work the first time.

In this picture I use a piece of 1/2" PVC pipe.  Not a good choice, next time I used a screwdriver to mix.  Try to remove most of the lumps.  I bet a paint mixer on a drill would work well.

Step 3: Pour the mix into the plastic water bottle.

Picture of Pour the mix into the plastic water bottle.
The reason for the water-bottle is to force as much mix as possible into the balloon. 
A funnel will not work to get the mix into the balloon, but it would work to get the mix into the plastic bottle. 
The bottle should be full or almost full of mix. 
Very messy work.
Rinse bottle off. 

Quickly go to next step as the plaster is hardening as we speak.

CarziG2 years ago
I finally go this right :D For anyone trying this here are the things I leanrt! Use medical P.O.P (plaster of Paris) not the art shop kind, it coats thicker and better.
I used the measurement of 250g x 150ml and it worked like a bomb!
I also used yellow balloons but found that the thinner the balloon the faster it set, so the thicker balloons are the way :D
Thank you for this once again Obediah!
CarziG2 years ago
Thank you so much for this :D I've had such a great deal of fun trying to make them! I just wanted to find out if someone perhaps has measurements for how much water by how much plaster? Also how long should I leave if for? :) Thank you!
y123212 years ago
i have a problem....after the plaster dries and i try to remove the balloon, the minute i cut the balloon the whole thing collapses because the balloon squeezes on the plaster. Any suggestions?
Obediah (author)  y123212 years ago
I believe that you might need to:
A) wait longer so the plaster is harder
B) Use a bit more plaster to make it stronger
C) when i popped it, i just cut a tiny hole in the end opposite the air valve of the balloon. and the balloon just peeled off by itself, and i just had to remove the last bits.
D) in making these, I was successful about 1 in three times, So failure is an option.
it's a challenge to great the right mix of water vs plaster, and the right amount of plaster total to use. And nothing sucks more than to have put in all that work to see it crumble. I would love to see a picture of the final when you do it!
Tetrafish5 years ago
When I was a little kid I asked my Dad about a large Easter Egg (a folding paper one)  "what kind of bird laid that egg?"  And he said an Ooh-Wow bird. X-)

As for the candy egg...  I think they inject or funnel the melted chocolate inside, spin twist and clamp or tape it closed, roll it around to get a good coating inside, then roll it around on cool/cold water to help harden the chocolate, (there probably might be a coating inside prior to injection, but maybe it wouldn't matter) then blow it up more to separate it, then pop it around the egg.  ....I'd guess.   I hope that wouldn't make a mess. <:-/

Perhaps a way to pump air into the balloon would be better, unless these are going to be for yourself ('cause you'd blow your own germs into it if you blew it up manually). :-p
Obediah (author)  Tetrafish5 years ago
Ithharden. Good try it this afternoon. I wonder how fast the chocolate hardens?  Can I re-melt and re-harden it?  Would it be better just to get a giant plastic egg as a mold rather than a balloon?
I also think it would be cool to make the giant egg with chocolate and fill it with smaller store bought easter eggs.  I wonder how to do that?

You reminded me that 3 years ago when I did the plaster egg, I would set it in a sink of water rather than on a pillow to harden.

Good point about the air pump VS my own air.
IF you could get the chocolate in the balloon to work - I'm not sure it wouldn't be too fragile unless you got a lot of chocolate in there - then it shouldn't be too hard to take a hot knife, cut it in half, fill it, then reseal with the same hot knife.  You could even decorate it with colored chocolate from the candy making supply. 

Geez, I'm talking myself into trying this now.  :)
Obediah (author) 5 years ago
Here's where I ask the Instructables Community for input...Plater seems very porous when painting.  I would love to get a smooth glossy, almost glass like finish if I could.  Is there something to coat plaster with to help with painting?  I've tried primer, but that didn't seem to do much.
You could try wax. If you can get a soft wax, such as surfboard or hockey wax (called sex wax), then you could make it glossy.
Obediah (author)  greenbean5 years ago
Can you paint wax?
Maybe if you melt it. I would just rub it on. If it is to rough after that, blow hot air at it to soften and smoothen it. Try this on something unimportant though because I haven't tried them.
finfan7 Obediah5 years ago
Try transparent polyurethane spray finish.  A few thin coatings would do it.
Obediah (author)  finfan75 years ago
I've got to try that.
Acidmoxy5 years ago
This method could perhaps be used to make chocolate eggs too, unless theheat of the melted chocolate made the balloons explode too frequently,but the chocolate would set a lot quicker than the plaster. :)
Obediah (author)  Acidmoxy5 years ago
Okay great, Now I HAVE to try this idea...and then I will HAVE to eat them.  And it will take several attempts to get the chocolate consistency just right.  I'm gonna get so fat.  But that might turn this project into something more marketable.  Great idea,  except for my waistline.
Waistlines are for pansies. Real men spend their days filling baloons with chocolate.And I'll be god damned if I'm not eating every last piece.
Obediah (author)  Acidmoxy5 years ago
Pansy am I?  Well I'll show you who's the macho man.  I'm gonna make the biggest chocolate egg you've ever seen, decorated with flowers, filled with cream and paint it two-toned pastel, and I'll call it lunch, then you won't be calling me a pansy anymore.
Obediah (author)  Obediah5 years ago
10:07 PM Saturday night; 
Chocolate Egg experiment.

Went horribly, horribly wrong.  Balloon burst, an explosion of chocolate, brown debris everywhere. 

Must try better quality balloons.

Going to a movie.
If there's one thing more macho than chocolate eggs, it's EXPLODING chocolate eggs.
Obediah (author)  Acidmoxy5 years ago
The lessons I learned after two horrible chocolate explosions.

1. I was smart to do this in the shower.  Easy cleanup.
2. Not smart to wear clothes, learned and fixed the 2nd time. 
3. As far as mistakes go, it's a tasty one.
4. Chocolate is oil based, and balloons are latex, and we all know what they say about using NON-oil based lubricants. 
finfan75 years ago
It would be awesome to combine this with the dragon egg technique. (
bptakoma5 years ago
How about blowing up the balloon first.  Pat the plaster overit.  You're sanding anyway, right?   I know you probablywouldn't get the same eggshell effect, but perhaps less risky.
Obediah (author)  bptakoma5 years ago

Interesting, what i do like about this method is the amazing smoothness the balloon gives it.  Teh only part i really need to sand is the tip where the nipple was. However If I were making Dinosaur/Monster/Alien eggs, this outside-the-balloon (outside the box?) idea might give it a real rough surface that would be more effective.

Carmelite5 years ago
 Nicely Done. I did these with water ballons three summers ago. Iwould make it with the exact same process, except I put them in a bucketof water.
Then, I drilled a hole in them and filled them up.
Let's just say I won the water balloon fight. :D

Oh and even if you use a transparent balloon, it will become opaque assoon as you cover the thing with a layer of plaster.
Obediah (author)  Carmelite5 years ago
The reason I suggest a transparent balloon is just that, so you can see when it is covered on the inside.  It needs to have no holes or streaks in the shell.
l8nite5 years ago
its your creation, if you want to splatter/speckle it GO 4 it !!  My wife looks at a painting of a sunset on water and says ...."why did you make the water orange and pink? I dont like it"
 pppffffft... she sure likes the green when it sells though !!!

   This is a really cool idea ! I'll have to remember this for the g-kids easter hunt !
thats a pretty smart wife you got there
rachel5 years ago
This is a really novel idea, I like it!
Kiteman5 years ago
Very nice project - the splatter effect is most spectacular...
Obediah (author)  Kiteman5 years ago
I will pass your comment onto my wife.  She may not see the Spectacularness of it...
Kiteman Obediah5 years ago
Tell her it's art.
ycc21065 years ago
Smart! =)