Fruiting your spawn to bulk substrate doesn’t have to be hard. Although there are many bulk substrate recipes online, this preparation method is simple, straightforward, widely available ingredients, and does not require pasteurization.


This substrate prep is based on the BucketTek method, which is not true pasteurization, yet is extremely effective because we are using non-nutrient containing ingredients (Coir and Vermiculite). Keep in mind that this recipe may be modified by using additional ingredients such as worm castings or manure, but when using these additives, it is smart to perform a full pasteurization before use.

Easy Bulk Substrate Preparation Instructions


  • 1 Brick of 100% Natural Coco Coir. (650grams)
  • 2 Quarts of Vermiculite
  • 1 cup of Gypsum – This ingredient is optional but provides calcium and sulfur, which is needed for healthy mycelium growth and also acts as a pH buffer.
  • 5 Gallon Bucket with Lid – Find this at Home Improvement Stores
  • 4 Quarts (one gallon) of Boiling Water. Tap water is fine, filtered water is better.

Step 1: Place the coco coir into a five gallon bucket. When using compressed coir bricks, it helps with hydration to break up the brick into smaller pieces.

Step 2: Add 2 quarts of vermiculite to the 5 gallon bucket.

Step 3: Place a large pot on the stove and add 4 quarts of water. Turn the burner to high and add gypsum to the water. Wait for the water to a boil.

Step 4: Remove the pot from the heat and stir the gypsum/water mix using a large spoon, then pour the hot water over the ingredients in the five gallon bucket.

Step 5: Place the lid on the bucket and allow to sit for 10 minutes. Once 10 minutes is up, remove the lid and stir up all of the ingredients using a large spoon. Be careful, the substrate will be very hot and steam will be released once the lid is opened.

Step 6: Place the lid back on the bucket and allow the substrate to cool overnight (4-6 hrs).

Step 7: Use it!

Have you had success with this recipe, do you have a variation? If so, we would love to hear from you. Leave a comment in the box below!


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