huey.bluey's Calculated Coir Tek
Purpose of the Calculated Coir TekThe purpose of this Calculated Coir Tek is to crack as few eggs as possible with the purpose of making our mushroom substrate with no extra material left over.
What is considered field capacity for a bulk substrate?Many people have different definitions of field capacity. Some people like a drier field capacity where only one or two drop(s) of water come out when you squeeze the expanded coir hard; Some like a wetter field capacity where a small stream or a couple drops of water come out when you squeeze it hard. This comes down to preference and how fluffy the given substrate material is. I would personally go for a few drops to a small stream with coco coir. But nothing TOO wet.
Quote:
"The fluffier a given substrate is, the more water will squeeze out. That's why with sawdust, I adjust so not one single drop comes out when squeezed as hard as I can. However, with coir, compost, manure, etc., If you squeeze really hard, a small stream should flow for only a second or two and then stop. Adjust as demonstrated in the casing layer video clip.
RR"
Expansion ratio of your coirHow much will your coir expand after water is added? This is an important question to ask as it will tell you what volume you will end up with. I do not measure out the water, since you are going to be feeling that out for field capacitance. This exotic wood zone coir I have says it will expand to 9-10L from an original size of (1000 cm
3 = 1 L). You can usually go by the label. Test on a sample of the coir 6+ grams is good. After my testing: 6.9 grams became 80ml. Therefore my ratio would be 0.08 expanded liters / 6.9 grams dry coir = 0.0115942. For 3 liters expanded coir I would need 3/(0.08/6.9) = 258.75 grams of dry coir. (I've since made a spreadsheet that calculates all these ratios automatically for myself

)
Keep the constants written down
0.08 expanded liters / 6.9 grams dry coir
0.04 L hot water / 6.9 grams dry coir (to FC)
Part Spawn to Part SubstrateThe next step is finding your ratio of spawn:substrate.
I would recommend a 1:3 or 1:4 for best results. Some people go all the way to 1:7 with great results. If the grain's health are questionable, keep it at 1:2 or 1:1.5. The sub's role here is primarily to keep the grains hydrated, not so much of a nutritional source (though it colonizes through it).
**Do not waste compost in cube tubs, they only eat grains.
Calculating total volume neededI start by first filling my tub with water to certain inch marks in the tub. Then writing down how many liters it took to get to each mark. For instance, my 20 quart Sterilite takes 4 Liters to get a 2 inch sub and 6 Liters to get a 3 inch sub. This gives you the target quantity of substrate + spawn you are aiming for.
Find spawn and substrate amountsTake your ratio, 1:2 in my case, and multiply by your target tub fill (6L to 3" depth).
1/3 * 6L = 2L spawn
2/3 * 6L = 4L substrateYou already know spawn is just fully colonized grain jars.
huey.bluey's substrate mix for cubensisMy 75% coir, 23% vermiculite, 2% gypsum mix
- 3/4 Wet Coco Coir
- 23/100 Vermiculite
- 1/50 Gypsum
*If you don't like vermiculite or gypsum then exclude those. Totally up to you. We consider the coir to be wet and expanded here.Final calculationsLets do some easy math using our recipe:
3/4 * 4 L = 3 L Wet Coco Coir
23/100 * 4 L = 0.92 L Vermiculite
1/50 * 4 L = 0.08 L GypsumSince coir will expand and we have it's ratio figured out (0.08 L / 6.9 grams). Divide the expanded form of coir by our ratio and get the dry volume.
3/(0.08/6.9) = 258.75 grams Dry CoirCalculate the water (approximate)I used 0.04 L hot water per 6.9 grams so:
258.75*(0.04/6.9) = 1.5 L hot water approximatelyMore water is necessary considering verm holds twice the water as coir.
Pasteurize with boiling water in a bucketThen mix your dry coir, vermiculite, and gypsum in a large bowl or bucket. Add boiling water from a tea kettle or your PC. Add more verm or coir if its too wet. Add the water slowly in parts, and test by hand.

Once you get the capacitance just right, put the lid on your bucket or cover the top and let sit for an hour. Mix it up, the substrate should have cooled but is still warm. Once the coir pasteurizes and cools to an internal temperature of 60-90'F you can follow the section on filling up tubs in the
Elementary Coir Tek.
Boom, no left overs! If you want a casing, leave some extra substrate in your bucket while you mix your sub and spawn. Then layer the rest on top. Or use a different recipe for the casing! (I would use 50% coir 50% verm for casing until I figure out peat casings) Cubensis doesn't necessitate a casing layer.
This calculated method should provide sterile conditions for your mushrooms and most importantly; waste nothing.
A few extra pointers- 1. (optional) Cook your vermiculite. Cook it at 350°F for 1 hour before using it. Even if its new, it can harbor contaminants in its many pours. Coir alone can be wet for months and never grow mold. Its the addition of dirty vermiculite that wasn't properly sterilized leading to cobweb among other contaminants. Some people say this is unnecessary and it probably is. But I do it anyway because it sits next to my grains.
**I recommend testing the expansion of the coir manually as it can be different between brands, and may not align perfectly with what is reported from the manufacturer.