Grain spawn is used to propagate mushrooms by inoculating bulk substrates such as hardwood, straw and for certain varieties manure/compost. One healthy jar of grain spawn can be expanded exponentially into 1000s of jars with a little work and proper sterile technique. Its best to use a flowhood or an S.A.B. (add:**How to make an S.A.B. **link here) when you're doing grain to grain transfers to expand your spawn.
We have two methods listed here which both work well. The first one is the simple method called "No Soak, No Simmer" that requires less work and involves less time waiting. The second method is the more common method which is also our favorite even though it takes a little more time and work.
Method 1: No Soak, No Simmer Grain Spawn-Easiest and Fastest Recipe
For a 1qt Mason jar of grain spawn (1lb)
1) Add 240g of whole oats or rye grain to a 1qt. Mason Jar
2) Add 230ml (230g) of water to the jar
Once you add the grain and water to the jars just put the lids that you modified back on. Pressure cook jars at 15psi for 1 hour and 30 minutes and then allow them to cool inside the cooker for a few hours until you can comfortably touch the sides. Once you can safely open the pressure cooker take out your spawm jars and shake them really well to evenly distribute the moisture while they are still nice and hot . Allow jars to cool to room temp and then inoculate with liquid culture, colonized grain spawn or our favorite a colonized agar wedge.