Purchase or find a container deep and wide enough to contain the pumpkin.
Pour baking soda into the bottom of the container. Place the pumpkin on top of the baking soda.
Pour baking soda on top of the pumpkin until it is completely submerged in the baking soda.
Cover the container and seal the lid. Place duck tape around the seal to prevent air from getting into the container. Air causes moisture and mold, interfering with the mummification process.
Keep the pumpkin sealed in the container for one week. Open the container and remove the baking soda.
Repeat the process of submerging the pumpkin in baking soda, using fresh baking soda and sealing the lid.
Wait 10 days to unseal the pumpkin. Remove the pumpkin from the container. Brush off baking soda that is stuck to the pumpkin with a dry towel. The pumpkin will appear smaller and shriveled.
Create a paper mache paste to wrap and mummify the pumpkin in. Bring 5 cups of water to a boil in a small saucepan. Add 1 cup of flour. Bring the mixture to a boil for three minutes, stirring while boiling.
Pour the paper mache paste into a bowl and allow it to cool for 10 minutes. The consistency of the paste should be thick and smooth, similar to school glue. Stir in 1 tsp. of salt to preserve the paper mache and to prevent molding.
Tear strips of newspaper about 6 inches long and 2 to 3 inches wide. Dip one strip of newspaper at a time into the paste so that both sides of the paper are coated. Hold the paper over the bowl and run your fingers down the paper to remove excess paste.
Coat your pumpkin from top to bottom with the paper mache. Smooth out wrinkles with your fingers. Coat the pumpkin with a second coat of paper mache, applying it horizontally around the width of the pumpkin from top to bottom. Smooth out wrinkles, as needed.
Allow the pumpkin to dry for at least four hours until the exterior is dry to the touch.