Urban Spore

How To Prepare Masters' Mix

king oyster mushrooms

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.

Learn to make mushroom fruiting blocks without hardwood using our equine mushroom mix guide in the link below.

Fully Colonised Pink Oyster Grow Kit

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.

Soy Hulls & Hardwood Together At Last

Sometimes it can be a challenge to find soy hulls & hardwood fuel pellets. Mushroom Media have

Step 1. Weigh Dry Ingredients

Using kitchen scales 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.

Hardwood fuel pellets in a bowl

Step 2. Add Water

Use kitchen scales to weigh water in grams for accuracy. 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. Learn how we fold grow bags for sterilisation in the link below.

making masters mix

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.

Learn how we load a pressure canner in the link below.

Choosing A Pressure Canner

The Presto 23 Quart Pressure Canner is an excellent option for sterilising media for mushroom growing.
It has capacity for sterilising up to 24 x half-pint mason jars.

Note: Using pressure canners for mushroom growing may void the warranty.

Step 4. Inoculate

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.

oyster mushroom grain spawn

Aseptic Technique

It’s important to adhere to aseptic technique when inoculating sterile media. Sterilised media is extremely prone to contamination.

Only objects that have been flame sterilised may make contact with the sterile media or grain spawn.

Alcohol can be used to sanatise and clean surfaces of micro-particles but is not suitable for sterilisation.

A face mask should be worn at all times. All work should be undertaken with a laminar flow hood when possible. In the absence of a flow hood a smaller enclosed space with minimal airflow, such as a bathroom may be used with varied results.

agar plate for mycology

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