So your spawn bag is fully colonized and you are ready to spawn to a bulk substrate in a mono-tub. While this step may seem insignificant, I wanted to test to see if the method of mixing your bulk sub and spawn made any difference to colonization time, yields, contamination, etc.

I was originally taught that during this step you would start with a layer of pasteurized substrate, then add a layer of colonized spawn, followed by a layer of substrate and so on; just like the layers of a cake.

Maybe I just got lazy, but somewhere along my mycology journey I switched to just pouring the spawn in the mono-tub, adding the pasteurized substrate, then mixing really well and adding a thin layer of substrate on the top to cover any exposed grains. 

So to layer or not to layer? That is the question.

Layer your substrate or mix

Don’t ask me why I decided to put this to the test using one tub instead of two, but I did. 

As you can see from this image, after 9 days in incubation, the side that was layered had nearly fully colonized and the side that was mixed was far less colonized. 

Additionally, I noticed some mold beginning to appear on the mixed side, so I nuked it with bleach for the sake of this experiment. 


Unfortunately, the mold came back like a ravenous charging rino and completely destroyed this tub.

I have no doubt that had the mixed side colonized faster, this contam would not have had an opportunity to form.

So, its settled then. Mixing your substrate will slow down colonization times. Layering your substrate is the way to go! 

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