Gypsum (Calcium Sulfate) for Mushroom Cultivation

Finely milled food‑grade gypsum supplies calcium and sulfur while helping substrates stay loose and pH‑stable. It is a staple additive for grain spawn, sawdust blocks and bulk mixes such as CVG.

Why Add Gypsum?

• Provides calcium for firm fruit bodies and balanced mycelial growth.
• Supplies sulfur, an essential trace element for enzymes and flavour compounds.
• Buffers pH, keeping substrates in the 6–7 range where most gourmet species thrive.
• Prevents grain kernels from sticking together, improving shake‑ability and colonisation speed.

Recommended Rates

• Grain spawn : 1–2 % of dry grain weight (about 5–10 g per dry kilogram or 1 tsp per dry quart).
• Bulk substrates (CVG, sawdust) : 5–10 % by volume or 2–5 % by dry weight.

Blend thoroughly before hydration or mix the powder into warm water for even distribution.

Pack Size

500g or 3kg resealable bag. Stored cool and dry, gypsum remains stable for years.

Basic Use

1. Weigh the desired amount.
2. Stir into dry ingredients or dissolve in your hydration water.
3. Proceed with pasteurisation or sterilisation as usual.

Tips

• Pair with calcium‑nitrate or bran only after small‑batch testing to fine‑tune your nutrient profile.
• Sift if clumps form; gypsum is hygroscopic and may absorb moisture during storage.