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Bulk Spawn and Casing Tek

Tamping substrate with a gloved hand

Items we'll need to case our bulk spawn corn. Drop cloth, corn jars, alcohol, saran wrap. 9x13 baking pans we'll use to case our bulk spawn in.


What we’ll need to create 4 13×9 birthday cakes.

2 x 6lb coir, vermiculite, & gypsum bulk substrate bags or your favorite equivalent.
basic 9x13 baking pan2 x 1qt Colonized Grain spawn jars.  We’ll split the colonized corn between the two pans.
4 x 13×9 baking pans. You’re looking for a basic Steel or aluminum rolled edge baking pan with no handles on the ends.

1 x pair of gloves.
70% alcohol spritz bottle.
plastic wrap with a slide cutter.
Cardboard, newspaper, etc to catch crumbs and make cleanup easier.


Place the four pans in the oven and bake them at 350° for 30 min.
Cheap steel baking pans are great. They’re easy to sterilize, compact while colonizing, no plastic liners required, and they slip in and out of your monotub without a mess. This minimizes the cleaning required to ready a monotub.

Mix (Spawning Grain to Bulk Substrate)rolled bagMixing 1 corn jar with 1 6lb bulk spawn bag.

While your pans are cooling, dump the contents of 1qt corn jar into your bulk spawn bag.  Roll the top down on your bag and mix corn and substrate together by squeezing the outside of the bag and shaking vigorously. A really good mix helps the mushy colonize the entire cake quickly. Increasing your chances for a successful grow.


Pour the substrate grain mix into the first two pans. Pat the mix to sculpt a smooth even top. Swipe your hand left and right if necessary to even things out.


Wrap half the width of the the cling wrap over your cake and continue looping under then over the pan two more times until it’s completely covered end to end. It will feel a little awkward at first.  This is done to keep moisture in the substrate and block out contaminants while the cake colonizes. Leave at least half a width of the cling wrap loose off the end for air exchange.  We highly recommend keeping spawn pans in a room with an air scrubber while they colonize.


With this simple tek you can reliably make contamination free bulk substrate cakes.  Once you’re cakes have completed colonizing drop them into your favorite monotub.


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