How to Make Fossils

Two Parts:Preparing a Mould MixtureCreating a Fossil

The term "fossil" refers to organic matter that has been preserved in the earth for thousands of years. Although creating authentic fossils of your own would take an extremely long time, you can make the next best thing at home using plaster. By placing objects in a mixture and letting it settle, you'll be able to replicate the basic process of fossilization overnight.

Part 1
Preparing a Mould Mixture

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    Choose a mixture. Although rubber cement, cement and even flour can be used to make a fossil mould, plaster of Paris is the recommended choice of material, as it's cheap and designed to be easy to use. If you're planning on presenting your fossil outdoors however, cement will increase the durability.
    • A 4.5lb box is approximately $5, and will offer you more plaster than you'll ever need for your fossilizing needs.[1]
    • Harder materials like cement aren't recommended for proper mixing bowls. Use a bowl you think is completely expendable.
    • A combination of flour with other materials like salt and coffee grounds can be used as well to a similar effect.[2]
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    Pour plaster and water together.[3] Regardless of the particular material you use, use two parts mixture to one part plaster. Get a mixing bowl and pour them in together. Although exact measurements are not necessary, you can use measuring cups from your kitchen for this step.
    • For most fossils, two cups of plaster and one cup water should give you all the mould you need. Double this recipe if your fossil objects are bigger and need more space.
    • If the plaster you purchased indicates it needs a different proportion of water, you should go with its recommendation. Certain brands and types of plaster may have individual preferences.
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    Stir your mixture until it becomes consistent.[4] Using a mixing spoon or a popsicle stick, stir in the mixing bowl until the water and plaster have become consistent throughout. By the end, the mixture should be thick and goopy without having excess plaster powder visible in the mix.
    • This is your chance to troubleshoot your mixture if there are any problems. If the mixture doesn't seem semi-solid and thick, add more plaster. If some of the plaster isn't joining the mixture, add water.

Part 2
Creating a Fossil

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    Collect objects to fossilize.[5] There are countless different objects you can choose to fossilize. Shells and animal bones are best for their distinctive shapes. Plants and leaves can be scooped up from the backyard or nearby park and fossilized as well. For the sake of demonstrating the fossilization process, you should choose something organic.
    • Plastic toys of bugs and animals should be used in lieu of the real thing.
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    Apply petroleum jelly to your object.[6] Petroleum jelly (or Vaseline) should be applied as a thin covering over the object you're going to fossilize. This will make it easier to dig out once you've let the mould settle. Wipe away any excess jelly. Having too much on the object will negatively affect the mixture's hardening process and muddle the imprint.
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    Pour your mould mixture into a foam cup. Take a paper cup and pour in your mixture until it's 3/4 full. Don't fill it up all the way, as you'll soon be placing the object in and shouldn't risk the cup overflowing.
    • If your fossil is bigger, a foam bowl or paper bag may be used as well.
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    Cast the fossil.[7] Once you have covered your object in petroleum jelly, push the object into the plaster mould. At this point, you have the option whether to imprint your specimen part way, or bury it completely. Imprinting it will create a mould to put on display, while a full bury will offer a chance to play archaeologist and dig it out.
    • If you're making fossils in a group, you should start with imprinting. Imprint fossils are more cost-effective and can be enjoyed as a group.[8]
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    Allow time for the mould fossil to harden. Wait until the mould has solidified before you go any further. Using plaster of Paris, the mixture should dry completely within a couple of hours.
    • Heating the mould at 250 degrees Fahrenheit for an hour will speed up the process of solidification.
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    Tear open the cup.[9] The up is used to give the mould its shape. once it's hardened, you'll want to dispose of the cup entirely. Using scissors or a knife, cut the cup from top to bottom and tear it away from your mould. This should leave you with a plaster block.
    • It is recommended you tear open the cup over a trash bin in order to trap excess sediment and limit the mess.[10]
    • Don't forget to put the paper cups in the compost when you're done using them.
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    Remove the mould for an imprint.[11] If you've pushed your object only partway into the mould, the petroleum jelly should allow you to pull it up without damaging the object. Be gentle and slowly pull it out with your fingers. If you're rough and fast with it, you may risk hurting the imprint or the object itself.
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    Weather the mould for authenticity. If you've left an imprint for decoration's sake, chiselling at the mould itself will make it look like you recently dug it up. Take a hammer and chip away at the sides and corners of your block. Add small dents and imperfections. Although you shouldn't go overboard with your chiselling, the weather-worn look will add to the effect of your fossil display.
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    Chisel out a buried fossil with a precision hammer. If you decided to bury the object completely in the mixture, you'll be able to play archaeologist. Take a chiselling hammer and tap away at the mould. Work your way around it and try to chisel out your fossil. Be careful not to accidentally chisel at the object itself. This experience reflects what it's like to dig up a real fossil.


  • Recently, 3D printing has become a valuable technology for recreating fossils. Though professional-quality 3D printers are still prohibitively expensive for all but the wealthiest individuals, cheaper options exist - for instance, some online communities offer access to the capabilities of a 3D printer for a monthly membership fee, while some institutions of higher education, like universities and even community colleges offer 3D printing for (relatively) cheap.
  • The process of fossilization is a large part of why we know so much about the pre-historic world. You should keep these implications in mind when you do this craft.[12]


  • Clean up a plaster mess as soon as you can. When it hardens, it's extremely difficult to clean.
  • Don't pour plaster of Paris down the sink or drain. It will solidify in your pipes and ruin the plumbing. Dispose of it in a trash can.

Things You'll Need=

  • A tub of plaster of Paris.[13]
  • Anything you would like to fossilize. This can be chicken bones or beach shells.
  • Dixie cups.
  • Petroleum jelly.
  • A measuring cup.
  • A mixing bowl and spoon.

Article Info

Categories: Rock Gem Mineral and Fossil Collecting