How to Extract Calcium from Eggshells for Your Plants

DIY Water-Soluble Calcium

gardening
DIY
Author

Cindy Achieng

Published

March 15, 2025

Why Water-Soluble Calcium?

Calcium is an essential nutrient for your plants, especially flowering plants like tomatoes, peppers, and roses. A lack of calcium can cause problems such as blossom end rot in tomatoes, stunted growth, and weak stems. To prevent these issues, it’s crucial to provide calcium in a form that plants can readily absorb.

Eggshells are a well-known source of calcium. Many gardeners crush eggshells and either add them to compost or sprinkle them directly onto the soil. While this method does release calcium, it takes a long time for the calcium to become available to plants.

If plants need calcium sooner, there is a better approach: Water-Soluble Calcium (WSCa).

What Is Water-Soluble Calcium (WSCa)?

Water-Soluble Calcium (WSCa) is a liquid calcium solution made by reacting eggshells with vinegar. This reaction breaks down calcium carbonate (CaCO₃) into calcium acetate, which plants can easily absorb. The resulting solution can be applied as a foliar spray or directly into the soil for quick uptake. In addition to being fast-acting, it is cost-effective and easy to make at home.

Let’s dive into the process!

How to Make Water-Soluble Calcium

Ingredients

  • Eggshells
  • Vinegar (white or apple cider vinegar)
  • Glass container
  • Measuring cup (optional)

Steps

  1. Collect the Eggshells – Store eggshells in a ziplock bag and keep them in the freezer until you have enough.
  2. Prepare the Eggshells – Wash and dry the eggshells. You can sun-dry them or heat them in the oven for faster drying.
  3. Crush the Eggshells – Grind the eggshells into a fine powder using a blender or mortar and pestle.
  4. Add Vinegar – Transfer the powdered eggshells into a glass jar. Ensure the jar is large enough to accommodate the reaction, as bubbling can cause overflow (don’t say I didn’t warn you!). It’s best to work in batches. Pour vinegar over the eggshell powder, making sure the powder is completely covered. A general guideline is a 1:10 ratio of eggshells to vinegar (e.g., 100g of eggshells to 1L of vinegar).
  5. Fermentation – Let the mixture sit in a loosely covered jar for 5-7 days. Bubbling indicates the reaction is still occurring. Do not seal the jar tightly, as gases need to escape, but also avoid leaving it open to prevent contamination.
  6. Strain and Store – Once the bubbling stops, strain the liquid and store it in a sealed container.

How to Use Water-Soluble Calcium

  • Dilution: Mix 1 tablespoon of WSCa per liter of water.

  • Application:

    • Foliar spray for fast absorption (apply in the evening).
    • Soil drench to support root uptake.
    • Ideal for tomatoes, peppers, and fruiting plants.

Final Tips & Warnings

  • Do not overapply; too much calcium can cause nutrient lockout.
  • Use in combination with other natural fertilisers for balanced nutrition.
  • Test on a small area before widespread use.

By making WSCa at home, you provide your plants with a fast-acting, eco-friendly calcium source while repurposing kitchen waste. Give it a try, and your plants will thank you!