Gypsum Fine Grade | Grain Spawn Substrate Supplementation
Gypsum Fine Grade | Grain Spawn Substrate Supplementation
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Enhance your cultivation success with our high-purity Fine Grade Gypsum
Ssourced from food-grade mineral additive essential for both mushroom growers and soil enthusiasts. This fine-grade calcium sulphate is a staple in the mycology world, trusted by cultivators to improve the quality of grain spawn and promote robust mycelial health from the very first stage of growth.
The Mycology Essential: Why Use Gypsum?
In mushroom cultivation, the physical structure of your substrate is just as important as its nutrient content. Our Gypsum is ultra-fine and food-safe, making it perfect for evenly coating and mixing through hydrated grain prior to sterilisation. One of its primary roles is acting as an anti-clumping agent; it keeps individual grains separate, which significantly increases the number of inoculation points and allows for faster, more even colonisation. Beyond texture, Gypsum provides essential calcium and sulphur—two key nutrients that act as building blocks for vigorous mycelium growth and help stabilise the pH levels of your substrate.
Benefits for Soil and Garden Health
While it is a "must-have" for the lab, Gypsum is equally valuable in the garden. It is a fantastic soil conditioner that helps break up heavy clay soils without altering the pH as dramatically as lime. By adding this mineral to your garden beds, you improve water penetration and aeration, creating an environment where roots—and beneficial soil microbes—can truly thrive.
Quality You Can Trust
Whether you are prepping jars for a gourmet grow or amending your backyard soil, our Gypsum offers a clean, reliable, and natural solution. It integrates seamlessly into any growing medium, ensuring your fungi and plants have access to the minerals they need for high-yield harvests and long-term vitality.
Benefits
Benefits
- Improves grain texture and flow
- Helps reduce grain sticking/clumping
- Enhances calcium and sulphur availability for mushroom
pH stabilising properties
- Suitable for sterilisation or pasteurisation
How do I use it?
How do I use it?
Add 1–2% by dry weight to hydrated grains before sterilisation. Mix thoroughly for best results. Commonly paired with millet, wheat, rye, or sorghum grain for gourmet mushroom spawn.
Available Sizes
Available Sizes
100g – Great for hobbyists & small batches
250g – Ideal for regular growers
500g – Cost-effective for ongoing projects
1KG – Best value for larger or frequent grows
Delivery Information
Delivery Information
- We ship from Tamborine Mountain, QLD using either AusPost or Aramex
- Fast dispatch within 1-2 business day (excluding Fridays) with express post options available
Why Customers Love Us
Australian Owned
Family Business
Sustainability

Hand-Grown on Tamborine Mountain
At Kai Kai Farm, we don't just sell kits and tonics—we use them every day. Founded by Quintin and Amy in the heart of the Scenic Rim, our mission is to make professional-grade mushroom cultivation and sustainable gardening accessible to everyone. From our no-spray gourmet mushrooms to our bio-active soil health range, every product is tested right here on the farm to ensure your growing journey is a success. When you shop with us, you’re supporting a local family business dedicated to a greener, more delicious planet.
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