How To Test Plastic Leak-Proof Bag With Pencils

by | Nov 8, 2021 | DIY, Life Hacks

Home » DIY » How To Test Plastic Leak-Proof Bag With Pencils


The plastic bag is made up of a long chain of molecules known as “Polymers”.This makes the plastic bag stretchy. When the sharpened pencils pierced through the plastic bag, these long chains of molecules around the pencils within a minute prevented the leak of water. This could be a helpful method to check a plastic leak-proof bag.

This tutorial will show how to check a plastic leak-proof bag with pencils at home.


We need the following supplies to build this science model


  • leak-proof bag
  • Sharpened Pencils
  • Water

Steps To Test Plastic Leak-Proof Bag

Step 1: Fill the plastic bag about ¾ of the way full of water and seal it shut.

seal it shut

Step 2: Hold the sharpened pencil in one hand while using the other hand to put the pencil through the plastic bag. Continue pushing it until the sharpened point of the pencil also comes out of the other side of the bag.

side of the bag

Step 3: repeat with more pencils and check any water spills out.

Plastic Leak Proof Bag And Pencil Science Experiment

No water spills out of the plastic bag!


Plastic bags are made up of polymer. Polymers have long, flexible chains of molecules. Hence, No water should spill out.

When you poke a sharp pencil through the bag, the pencil slides in between the chain of molecules that make up the polymer. The Molecule chains make the seal around the pencil that won’t let the water out.



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