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Sea Shell Mosaics Stones by Brenda Ponnay for

Sea Shell Mosaics

By Brenda Ponnay

Remember summer forever with this fun seashell craft!

shell mosaic

I had a passel of kids at my house today for a craft project–seven of them, actually. I might as well call it craft camp. Usually organizing a craft for kids ages two through eleven can be quite a challenge, if not impossible, but today went surprisingly well. We made classic plaster-of-Paris mosaics in pie tins but added a special summer twist by arranging colorful shells and sea glass to create a beachy scene. It was quick and easy to prepare and occupied everyone happily for several hours. I’d say that’s a summer win!


We’ve been collecting shells and sea glass all summer so this was the perfect craft for us. We also picked up some tiny clear marbles and faux pearls from a local craft store to simulate the bubbles that you often see in beach waves.

All you’ll need for this simple craft is:

  • an aluminum pie pan
  • a big plastic bucket for mixing
  • a 1-cup measure
  • wooden stir sticks
  • a collection of shells and sea bits
  • some plaster of Paris*
  • a decoupage sealer (like Mod Podge)

Plaster of Paris is usually available at any craft or hardware store. It might seem a bit intimidating when you find yourself hefting around a giant plastic tub of cement powder but it’s actually quite easy to mix and use. If you can make pancakes from a box mix, you can make plaster of Paris.

* We would advise parents to mix the ingredients for this project when the kids aren’t around. Please be sure to read and follow the safety precautions for this or any product recommended here.

The mix is a simple ratio: two parts cement powder to one part water. You mix it up in a plastic tub or bucket, stir it thoroughly and then pour into your tins. You can pour it into any container, really. The pie pans work well because once the plaster hardens, they are easy to peel off, leaving you with a perfect little round shape.

smorgasboard of sea bits

Earlier in the week my daughter and I had sorted all of our shells into empty egg cartons. We sorted by color and size, and that was a fun activity in itself, but totally not necessary. I found that the shells in the egg cartons were really easy to carry and set up. I arranged them all in a row on a long table and it worked great for the kids to file by for their selections.


After everyone picked out their favorite bits we set to work pressing them into the plaster of Paris. The instructions on the tub tell you to wait until the plaster is starting to harden before you press anything into it, but on a hot day like today I didn’t really have to tell anyone to wait. The plaster was very forgiving and the kids had no trouble at all making their masterpieces.

flame shoes

Everyone had so much fun I let them pour the extra plaster into some odd jar lids I had handy to make little mini mosaics. I think we could have made these all day long but lunchtime crept up on us, which was perfect because while we pigged out on pizza the mosaics dried in the sun.

patiently waiting for the plaster of paris to dry

pretty shell pies drying in the sun

a finishing coat of mod podge

Before they were completely hardened, we popped them out of their tins and broke off all the rough edges along the sides. You could sand them too but we didn’t really need to. The important thing to remember is to break off the rough edges while they are still somewhat crumbly because if you wait too long the plaster gets hard and could crack and break under too much stress.

I also added a coat of decoupage sealer to some of them because I thought the shells looked prettier when they were shiny, but this is optional.

ta dah!

When the mosaics were completely dry, I wrapped them up in tissue and sent them home with the kids. I think the mosaics will make nice garden decorations or even something pretty to put up on a shelf. Either way, they are a great way to remember all the fun of summer.

About the Author

Brenda Ponnay

Brenda Ponnay is a stealthy secret agent who juggles parenthood to her adorable daughter by day and freelance graphic design/illustration by night. Whether it’s painting, baking, drawing, mak...

Brenda Ponnay is a stealthy secret agent who juggles parenthood to her adorable daughter by day and freelance graphic design/illustration by night. Whether it’s painting, baking, drawing, making castles out of cardboard boxes or just doing the laundry with flair, Brenda Ponnay has learned that what really makes her happy is being creative every single day.

You can read about all her crazy adventures on her personal blog: Secret Agent Josephine.

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  • Sara

    July 31, 2009 at 1:52 am

    What a great idea! I love this craft and will try it soon. I’m thinking of doing one with a bunch of rocks we’ve collected. Thanks!

  • eeloh

    August 7, 2009 at 7:46 am

    Fantastic! I have been collecting broken crockery for years now and it’s lying in a tub waiting for me to do something with. I also bought Plaster of Paris about 5 years ago but was too intimidated to do anything with it. If I can find it, I will follow your instructions.
    The pie plates are a god idea that have got me thinking maybe silicon bakeware could be good… I remember holidaying in New Zealand and seeing in a couple of gift shops some heart-shaped mosaics set in plaster of Paris, and there was a fabric loop set into the plaster so you could hang them up.
    Thank you for this.

  • Jessica G

    July 20, 2013 at 4:51 pm

    Wondering how much plaster of Paris you put in the pie plates? Half way full or all the way? Thanks!

  • Jessica G

    June 7, 2014 at 10:09 am

    I like to fill the pie pans / regular size. Takes longer to set up,, but they look nice. I also prefer water vs sea water, hoped this helps.

  • Michelle

    August 19, 2014 at 7:16 pm

    We just did these! We used 2 cups Plaster of Paris to 1 cup of water. Got the circle tins from the dollar tree 2 for .50.. My only concern / question is. Once they are sealed can they get wet? From what I am reading they are just decorative / can’t get wet.

  • Brenda

    August 19, 2014 at 9:28 pm

    Yes, I think they should be fine getting wet. We put ours in the garden and they’ve held up pretty well. Of course a sealer or some kind of clear resin would help even more but make sure you do that in a well-ventilated area because sealers can stink!  Best of luck!

  • brigett

    May 5, 2015 at 7:35 pm

    How Did You Weather PROOF them. The grandkids made some and water seems to wash away the plaster.

  • Brenda

    May 5, 2015 at 11:21 pm

    The simple answer is I didn’t. We don’t get much rain here in California and it wasn’t an issue but if I lived in a wet climate I would probably coat them with a resin. Here’s a video that might help:

  • Stephanie

    July 2, 2015 at 10:48 am

    Could you add food coloring to the plaster of Paris? I have never worked with it before, but thought it would be cute to add some color.

  • Mary

    September 18, 2015 at 4:24 pm

    Arggh!! I tried this with my kids and I think we may have let the plaster harden too long. The tiles they were using didn’t go into the plaster. Is it ok to let the items sink into the plaster?

  • Trisha

    September 19, 2015 at 1:05 pm

    I need stepping stones for the garden and I am afraid that Plaster of Paris would not be strong enough. I know cement would. And how long would they last?