1 Batch size
How big is this mix?
2 Recipe
Sawdust + soy hull make up the dry base (should total 100%). Bran and gypsum are added on top of the base.
Shopping list & mix
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How the recipe math works
No black box — here's exactly what the calculator does.
Base vs. additives
The base is your bulk carbon source, split between hardwood sawdust and soy hull pellets (they should add up to 100%). Bran and gypsum are then added on top of the base weight — so a 5 lb base with 20% bran and 1% gypsum becomes 6.05 lb of total dry ingredients before water. That matches how most growers describe and weigh a recipe.
Hydration to field capacity
To hit a target moisture content M, water added = M ÷ (1 − M) × total dry weight. At 60% moisture that's 1.5× the dry weight in water, so a hydrated block ends around 2.5× its dry weight. "Field capacity" means fully hydrated but not dripping when squeezed firmly — a drop or two at most.
Why these recipes
Masters Mix (50/50 hardwood sawdust and soy hull, ~1% gypsum) is the go-to for oyster, lion's mane, and many gourmet species — the soy hull supplies nitrogen so you skip separate bran. Supplemented sawdust (sawdust + ~10–20% wheat or oat bran) is the classic for shiitake and works well for many wood-lovers. Higher supplementation raises yield but also raises contamination risk if your sterilization isn't dialed in.
Common substrate recipes at a glance
| Recipe | Make-up (dry) | Good for |
|---|---|---|
| Masters Mix | 50% hardwood sawdust · 50% soy hull · ~1% gypsum | Oyster, lion's mane, most gourmet |
| Supplemented sawdust | Hardwood sawdust · 10–20% bran · ~1% gypsum | Shiitake, king oyster, wood-lovers |
| Soy hull only | 100% soy hull · ~1% gypsum | Cheap, fast oyster blocks |
| Straw pellets | 100% straw pellets | Oyster (low-cost, lower yield) |
Frequently asked questions
What is Masters Mix for mushrooms?
Masters Mix is a popular gourmet-mushroom substrate of 50% hardwood sawdust and 50% soy hull pellets by dry weight, usually with about 1% gypsum, hydrated to roughly 60% moisture (field capacity). The soy hull supplies the nitrogen supplementation, so no separate bran is needed.
How much water do I add to mushroom substrate?
To reach a target moisture content M, add water equal to M divided by (1 minus M) times the total dry weight. At 60% moisture that is 1.5 times the dry weight in water, so the hydrated substrate weighs about 2.5 times its dry weight.
How much gypsum should I add to mushroom substrate?
A common rate is about 1% of the dry substrate weight. Gypsum (calcium sulfate) adds calcium and sulfur, buffers pH, and reduces clumping so the substrate stays loose and well aerated.
Ranges are general guidance from common cultivation practice, not guarantees — your results vary with strain, supplementation, sterilization, and conditions. Always sterilize supplemented substrate properly. Mycro is for legal culinary & medicinal mushrooms only.