Sterilized Master's Mix Bag 5 lbs
Sterilized Master's Mix Bag 5 lbs is backordered and will ship as soon as it is back in stock.
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Description
Description
Ready-to-inoculate. 100% contamination-free. Trusted by commercial growers.
Our Sterilized Master's Mix Bag is the same optimized substrate we use in our own professional grow blocks — now ready for your bench. This 5 lb bag of pre-hydrated, pH-balanced hardwood sawdust and soy hull blend is pressure-sterilized at 18 PSI for 2.5 hours, so it arrives completely contaminant-free and ready to colonize. Just add your colonized grain spawn, seal it back up, and let your mycelium run. It's the fastest, most reliable path to fruiting nearly 90% of gourmet and medicinal wood-loving mushrooms.
At a glance
- 5 lb optimized Master's Mix (hardwood sawdust + soy hull blend)
- Pre-hydrated & pH-balanced for peak mycelium growth
- Pressure-sterilized at 18 PSI for 2.5 hours
- Sealed in a heavy-duty 0.5-micron 14A filter patch bag
- Ready to use — no mixing, hydrating, or prep needed
- Ideal for lion's mane, oyster, pioppino, chestnut & more
What is Master's Mix?
Master's Mix is a nutrient-dense, fully sterilized substrate made from hardwood sawdust and soy hulls — the gold-standard blend for wood-loving gourmet and medicinal mushrooms. Because it's sterilized rather than pasteurized, it carries far more nutrition than coir-based bulk substrate, which translates to bigger flushes and stronger yields. The trade-off is that it must stay sealed and be handled with sterile technique. It is inoculated directly inside the sealed bag with colonized grain spawn, not mixed in an open tub.
Important — keep it sealed. Unlike coir-based bulk substrate (used in non-sterile conditions as a tub mix or top casing layer), Master's Mix is not meant to be exposed to open air or mixed in an unsterile tub. Doing so invites contamination and defeats the purpose of sterilization. Add your spawn directly into the sealed bag, let it fully colonize, then fruit by cutting the bag open or transferring the colonized block to a clean fruiting chamber.
How to use your Master's Mix bag
- Work in front of a flow hood or inside a still air box to keep things sterile.
- Add your colonized grain spawn directly into the bag through the filter-patch opening.
- Re-seal the bag (heat seal or fold-and-clip) and shake gently to distribute the spawn.
- Incubate at 70–75°F in the dark until the block is fully colonized.
- Cut the bag open and introduce fresh air and indirect light to trigger fruiting.
How much grain spawn do I need? A single 5 LB colonized grain spawn bag will inoculate roughly 12–13 of these Master's Mix bags. Because the substrate is fully sterilized, a lighter spawn rate works well — though a heavier rate will colonize faster if you want quicker turnaround.
What can you grow?
Master's Mix is built for wood-loving species. It performs beautifully with:
- Lion's Mane
- Oyster mushrooms (blue, gold, pink, king and more)
- Pioppino & Chestnut
- Shiitake, Reishi, Maitake and other hardwood-loving varieties
Frequently asked questions
What is Master's Mix made of?
Master's Mix is a blend of hardwood sawdust and soy hulls, pre-hydrated to the ideal moisture content and pH-balanced for vigorous colonization. Each 5 lb bag is pressure-sterilized at 18 PSI for 2.5 hours and sealed in a 0.5-micron 14A filter-patch bag.
How do I inoculate a Master's Mix bag?
Work in front of a flow hood or inside a still air box. Add your colonized grain spawn directly into the sealed bag, re-seal it, and shake gently to distribute the spawn. Keep the bag sealed and incubate until fully colonized — never mix it in an open tub.
How much grain spawn do I need per bag?
One 5 LB colonized grain spawn bag inoculates approximately 12–13 of these Master's Mix bags. Since the substrate is fully sterilized, a lighter spawn rate works fine, but you can use more spawn per bag for faster colonization.
What mushrooms can I grow with it?
Master's Mix is ideal for wood-loving gourmet and medicinal species including lion's mane, all oyster varieties, pioppino, chestnut, shiitake, reishi, and maitake. It supports nearly 90% of popular gourmet and medicinal mushrooms.
Can I use Master's Mix in a monotub or mix it in open air?
No. Master's Mix is a sterilized substrate meant to stay sealed and be inoculated with sterile technique. Exposing it to open air or mixing it into a tub invites contamination. For monotub and casing-layer use, choose a coir-based bulk substrate instead.
How long does colonization take?
Most wood-loving species fully colonize a 5 lb block in about 2–4 weeks at 70–75°F, with slower species like shiitake and reishi taking longer. Timing varies with strain, spawn rate, and temperature.
Do you offer wholesale pricing?
Yes. For bulk orders of 10 bags or more, email us for wholesale pricing.
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Let customers speak for us
I think these are the best co2 boost bags on the market especially the price. More bang for your buck. My buds have been alot bigger, and alot more dense, stacking like a roll of silver coins! And alot more of a yield too! I will always use these co2 bags in every grow, they are definitely worth it! Unless you like fox tailed loose and airy buds!
These pellets work very well. Especially if you do no-low heat drying. Also helped,e save some that got soggy. I put a pinch of the pellets in the jar, and they dried up overnight.
These work, 2-3 per oz of dried mushrooms. Keeping them cracker dry.
Thank you for the fast shipping and awesome packaging! Love the insulated bags and ice packs! I am seeing some extremely aggressive growth in my sawdust bags after only 3 days! I have found my new spawn vendor! Please keep everything in stock! So hard to find good grain spawn these days without waiting a month.
I injected 2cc's into this 6 days ago, noticed first signs on day 4.
The unit came packed very well and easily assembled. My order did have an issue in that I was given a deficiency in the number of long screws I needed to complete the build. A quick email to customer service had my screws i the mail ASAP. Perfectly executed and best case scenario for an issue like this. SO far the unit operates as advertised and is a major upgrade to my home mycology process. I would recommend this product to anyone who wants a nice laminar flowhood but is not so inclined to design and build it from scratch. Components are well constructed and of good quality materials.
Super accurate. I use for each strand of research I do- a qc must!!!!
I inoculated on 3-18-26...fast forward to 6-1-26...I received my 28 quart monotub right on time..I took the cake out of the all in one grow bag best thing I could've done...I got to see how hyphae knots form them I got to see the primordia form..then I consulted with Midwest grow they said in two weeks I will have pins.. they were spot on..I'm extremely satisfied with this company best in the business...and now fruits...ty Midwest grow...
I injected about 3ccs of a liquid culture I had into this jar and within a day or two I could already see it expanding. It’s convenient that it comes with a stir bar already in the jar, make it easy to swirl around a couple times a day. I’m currently awaiting my agar results to determine if it’s 100% clean, but I don’t see any contamination. Highly recommend if you want to expand your LC and make it go further.
Have all the tools I need. Thanks, Midwest. I'm new to the world of fungi, but your help is appreciated.
I was getting alot of contam with northspore boomr bag strait garbage company. Contamination central at northspore almost everything contams. I tried a couple other companies then tried this blackcow. Its black gold Texas T the biggest dummy in the world will get massive flushes with this. The grain bags are awesome too and sterilized right. I went 14/14 on the grain bags. Midwest know what they are doing and even the packaging is next lvl everything double bagged. I only buy from midwest it's worth every cent
It's been several days since the Ecosphere arrived and I set it up, and I'm still amazed at all I got for the price: heater, fan, humidifier, two plug-in timers, two foil trays, and, of course, the five-tier tent with shelves and the plastic cover. Oh, and the LED light strip and the round air filters. It's everything I need right now, and I've started the growing process. It's a crazy good deal for the price. I'm new to mushroom growing, and I'm thrilled that I bought this setup as a start. Just plain wonderful.
Fast and easy colonization! These grain jars showed growth after just 10 days. My previous efforts with the all-in-one bags are taking MUCH longer but also working. Thank you Midwest Grow Kits 🙏
I love the people and the products. The people at MWGK clearly care about the integrity of the community they serve.
