Water Soluble Calcium (WCA) is a core input in Korean Natural Farming (KNF) and JADAM regenerative agriculture. It is created by fermenting toasted eggshells in vinegar to convert calcium carbonate into a plant-available form. WCA supports strong cell structure, healthy soil, and rapid growth phases in the garden. This guide explains the science behind WCA, why growers use it, and how to make it at home.
What Is WCA and Why Do Gardeners Use It?
Eggshells are primarily made of calcium carbonate, which is not immediately available to plants. Through fermentation with vinegar, the calcium is transformed into calcium acetate, a form that dissolves in water and becomes accessible much more quickly than raw minerals.
WCA is used during rapid growth periods, the transition from vegetative growth to early flower, and when plants are building new tissue. It can be applied as a foliar spray or soil drench, depending on the gardener’s goals.
Why Toasting the Eggshells Matters
Toasting eggshells removes membranes, reduces odors, and helps break down the shell structure. The light browning increases reactivity with vinegar, allowing the fermentation process to proceed cleanly and efficiently. Over-toasting or burning should be avoided, as blackened shells reduce available calcium.
Why Vinegar Is Used
Vinegar contains acetic acid, which reacts with calcium carbonate to create calcium acetate, water, and carbon dioxide. The bubbling reaction that occurs during the brew is the release of carbon dioxide as the vinegar breaks down the calcium.
This process mimics natural chemistry in the soil, where root exudates and microbial acids break down minerals. Using vinegar accelerates the conversion so the calcium becomes available within days.
When to Use WCA in the Garden
Gardeners typically use WCA during:
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Late vegetative growth
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Early flower transition
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Periods of rapid stem and leaf development
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General structural support phases
WCA is not typically applied heavily in late flower. Both foliar and soil applications are effective depending on plant stage and system.
How to Make Water Soluble Calcium (WCA)
What You Need
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At least 12 eggshells
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Apple cider vinegar
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Skillet or cast-iron pan
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Quart-size mason jar
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Cheesecloth or paper towel
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Rubber band
Ratio
1 part toasted eggshells to 10 parts vinegar
Step-by-Step Instructions
1. Crush the eggshells
Break the shells into small pieces (1 cm or smaller). Smaller pieces increase surface area and improve the reaction.
2. Toast the shells
Place the crushed shells in a skillet on medium heat. Stir continuously for about 5 minutes until they turn light brown.
3. Cool completely
Spread the shells out to cool completely before adding to the jar.
4. Transfer to the mason jar
Add the toasted shells to your jar.
5. Add vinegar slowly
Pour vinegar slowly into the jar. The mixture will bubble as carbon dioxide escapes. Pause halfway to allow bubbling to settle, then continue pouring.
6. Cover the jar
Use cheesecloth or a clean cloth secured with a rubber band. Do not seal tightly; the reaction needs ventilation.
7. Ferment 5–11 days
Store at room temperature, out of direct sunlight. When bubbling slows and shells settle, the WCA is ready.
8. Strain and store
Strain out solids and store the finished WCA in a clean jar.
How to Use WCA
Foliar Spray
Rate: 1 teaspoon per 1 gallon of water
Spray at dusk outdoors or immediately after lights off indoors. Avoid spraying in direct sunlight or high heat. Apply as a fine mist over and under leaves.
Soil Drench
Rate: 1 teaspoon per 1 gallon of water
Apply directly around the base of the plant. Aim for about 10% runoff to ensure even distribution. Wipe up standing water to avoid excess humidity.
Regenerative Notes
WCA fits within regenerative gardening principles: using what your environment already provides and converting it into valuable plant inputs. Eggshells, often discarded as waste, become a resource. This creates a closed-loop system that supports healthier soil, less waste, and greater self-reliance.
FDA Disclaimer
These statements have not been evaluated by the Food and Drug Administration. This content is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. The Federal Food, Drug, and Cosmetic Act requires this notice.