How To Make
Masters' Mix Substrate

Learn The Basics about Masters' Mix Substrate

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What Is Masters' Mix?

Masters’ Mix is a substrate blend pioneered by TR Davis of Earth Angel Mushrooms. 

It’s blend of hardwood fuel pellets (HWFP) and soy hulls. It colonises quickly and yields highly. 

Additionally it encourages a larger than average first flush allowing for quick turnover. 

Masters’ mix is heavily supplemented and will require sterilisation.

Does Masters' Mix Need Sterilising?

Masters’ Mix is a highly supplemented substrate mix and requires sterilisation for consistent results. 

Once sterilised the substrate is extremely prone to contamination due to being both nutrient dense and without a living microbiome. Sterilised media should always be inoculated using aseptic technique. 

In the absence of a flow hood the transfers can be done in space with minimal airflow, like a bathroom for example. 

What You'll Need

To make masters’ mix you will need an equal weight of soy hulls and hardwood fuel pellets. This is to be hydrated to 60%. Use the following recipe to produce 2.3 kg of substrate which is inoculated with 200 grams of grain spawn.

  • 450 grams soy hulls
  • 450 grams hardwood fuel pellets
  • 1.4 litres water
  • Mushroom grow bag 
  • Or Glass Jar

Step 1. Weigh Dry Ingredients

Weigh each of the dry ingredients. Mix together thoroughly before adding water.

If using a mushroom grow bag I recommend mixing the substrate directly in the bag. This recipe is ideal for filling 1 x [20x12cm] bag or 2 x [13x12cm] bags.

If using a glass jar we recommend keeping the size small due to a lack of ventilation. Ensure that a hole is placed in the lid with a micropore tape filter in place.

Soy hulls for mushroom growing

Step 2. Add Water

Weigh water with scales. Add water to the dry ingredients in the mushroom grow bag. Leave sit for 5 minutes to allow for the dry ingredients to absorb the water.

Now the bags are ready for folding. Mushroom grow bags do not require sealing before sterilisation. Learn how we fold mushroom grow bags in the following guide.

Step 3. Sterilise

Once the substrate has begun to absorb water the grow bag can be folded over itself and packed into the pressure cooker for sterilising. 

Alternatively, if you are growing in glass jars I recommend creating a channel within each jar using the handle of a spoon. After sterilisation this channel will be be filled with grain spawn.

Sterilise the substrate for a minimum of 90 minutes. If you are using an electric bench-top pressure cooker you may need to extend cooking times.

Step 4. Inoculate With Grain Spawn

Allow the pressure cooker to depressurise naturally. Wait a minimum of 2 hours before removing the lid. Any sudden changes in temperature will result in broken grow bags.

The cooled substrate can be inoculated with grain spawn using aseptic technique. In the absence of a flow hood an enclosed space with minimal airflow should be used to undertake the grain spawn transfer.

Can I Use An Instapot?

It’s not essential to have access to a stove-top pressure cooker or canner. An instapot or electric bench-top pressure cooker can be used instead. 

An instapot will often only reach approximately 7 – 8 PSI and for this reason sterilisation times for preparing grain spawn may need to be extended by 30 minutes.

A typical instapot will fit 4 spawning jars per cycle.

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