Preparing spawn bags full of spawn or fruiting substrate without using a HEPA filter.
Why Use Spawn Bags?
Regardless of the type of mushroom that one wants to grow, spawn bags provide an excellent solution to handle many pounds of substrate in a totally sterile environment with relative ease. Spawn bags can be used to colonize either spawn or the final fruiting substrate (which can then be laid in a tray if desired). As a cultivation tool for the colonizing the fruiting substrate, spawn bags greatly simplify the process of bulk growing, reducing the chance of failure and speeding the growing cycle by one or two weeks since the spawning process is bypassed entirely.
The books covering spawn bag methodologies describe usage assuming one has access to a HEPA filtered flow hood, so one can easily be intimidated assuming spawn bags are in the domain of professional growers only. Nothing, though, could be further from the truth!
One doesn't need a HEPA filter as I show below, and using spawn bags is a pretty cheap way to make things a lot easier and less prone to contamination! Large spawn bags, holding over a gallon of substrate and complete with a breathing filter patch, can be had online for as little as a quarter a piece bought in bulk (see www.sporeworks.com). Additionally, a 12"-wide impulse sealer, as required to properly seal the bags, can be found on ebay for about $25 plus shipping (look for one with a 2mm or wider seal). And once one is set up with spawn bags, a single large 140ml syringe injection can take the place of 80 or more smaller injections one would require using PF half pint jars, saving a lot of time. Below I have simplified the process of preparing spawn bags without the use of a HEPA filter using pictures.
Step 1 - Place duct tape covered by masking tape on the spawn bag directly opposite the filter patch (never cover or inject through the filter patch). Tape on the bag serves as an injection reinforcement platform. The footprint of the tape should be at least as big as the filter patch on the opposite side of the bag. Any other thick tape that can withstand pressure cooking can also be used. Although I do not have any experience with them, I have been told that some fancy foam tapes are self-sealing so that when the inoculation needle is removed they automatically seal shut. Such a tape could eliminate the need for hot glue as shown later.
Step 2 - Load the bags with the final fruiting substrate. The substrate should not appear significantly wetter on the bottom than the sides. Any sign of standing water is a sign of certain failure. The material should have a light and airy texture totally unlike mud. Vermiculite should be liberally added as needed to improve the texture of the substrate if required to achieve a light substrate.
Step 3 - Clean the inside flaps with a paper towel if necessary and tape the sides tidily if desired. Remember you'll want the bag flaps to lay flat like they came, not all wrinkled up, and you don't want substrate to impede forming an airtight seal so keep the inside clean.
Step 4 - Load the bags in the pressure cooker. The bags should be loaded such that the flaps are folded down the sides and flipped back up. You want to have easy access to the bag flaps so they can be sealed quickly and with little effort when the time comes. Put metal band separators between the bags to ensure even steam penetration. The bags can be against the pressure cooker walls, but if one has a gas stove, you'll need to elevate the floor separator an inch or two or else flames can lick the sides and cause the bags to melt. Multiple levels of bags should be rotated 90 degrees for better steam penetration.
Step 5 - Pressure cook the bags for 3 to 4 hours. If a single large spawn bag is used, one might be able to get away with only 2 hours.
Step 6 - Allow at least an hour for the cooker to partially cool. While the cooker is cooling, spray the room used for sealing the bags with Oust or Lysol to clean the air. Put on a facial breather mask and rubber gloves. Wash the outside of the gloves with rubbing alcohol. Bring the cooker in the cleaned room and seal the bags. The bags must be sealed without allowing any outside air in them. It is best to seal them without moving the bags or moving them as little as possible to prevent outside air from entering them.
Step 7 - Cooling and self-inflation of the bags. Inflation of the bags is essential to mixing the inoculants, so air must be encouraged to enter the bag through the filter patch. The good news is that the bags will partially inflate on their own if hung up to cool. Rubber-footed wood clamps are great to hang up cooling bags so they may self-inflate.
Step 8 - Once the bags have totally cooled (12 hours) they can be injected with liquid culture. Again in a clean room sprayed with Oust and wearing facial mask and gloves, plug in your hot glue gun to heat it up. Using an alcohol-soaked cotton ball, rub the tape reinforcement injection site with rubbing alcohol. Inject through the tape reinforcement. Typically a large spawn bag can be injected with a full 140mls of live culture. After pulling out the needle immediately seal the hole with a blob of hot glue over the tape (this is not required for self-sealing tapes). Allow the glue to cool completely. Knead the contents of the bag mixing the inoculants throughout. Put the bags up and watch them grow! They should completely colonize in only 7 to 14 days! Once colonized the content can be used for spawn or laid in trays as a bulk substrate. For a super easy tray, sideways incubation turns the spawn bag itself into an ideal tray liner! One only needs to place the bag in a tray sideways, cut open the top side, case, and you are done.
The Proof Is in the Pictures! Lastly, here are some pictures of flushes made possible using liquid culture to inoculate the fruiting substrate contained in spawn bags as outlined above.
Ecuadorian Cubensis and Ausi Pan Cyans
Young Reishi Block and Shiitake
Clarifications: Blue Helix I am using the a 22-quart Mirro pressure canner. These can be had online for about $75 plus shipping. They last forever and easily hold four large, full spawn bags stacked in two layers (about 25 wet pounds of substrate). A new o-ring is needed every hundred or two hours of cooking or else they start to lose steam through the o-ring. New o-rings run about $15 and can be found all sorts of places.
Blue Helix Pasteurization is a way to prepare a relatively low nutrient substrate for bulk growing, but if you use spawn bags to pasteurize, you are thinking too narrowly. When you use a spawn bag, prepare an OPTIMAL mixture of compost, manure, vermiculite, grains, oils, etc. for your substrate. Don't limit yourself. Sure compost is fine for bulk grows with spawn, but if your are going sterile, why limit yourself? Using the sterility of spawn bags and by adding wild bird seed, rye, black mustard, rye grass seed, or other seeds to the mix, you can create a much richer and higher yielding substrate. I like to add about 20% by weight wild bird seed (uncooked) to the compost or manure along with some black mustard seed for oils. If you want a potency boost to your cubensis, for example, you can add 3% by weight of Stevia tea leaves! You can create the most perfect fruiting substrate in the world without having a clean room.
mycofile Hey blue, just thought I'd throw this tip at you. You mention laying the fruiting substrate out in trays after colonizing in the spawn bag, which will often require some crumbling/breaking of the substrate. Well, if your tray is close the size of the lay flat dimensions of the bag, you can just set the bag in the tray while it colonizes, and the substrate will already be in the perfect shape of your tray. Just remove from bag and set in tray. Kinda like using your tray as a mold for the substrate bag. I've also done this with large trays (or small bags) by laying several bags flat in one tray. Another thing that's useful about this is when it's time to case, you can just cut the bag off, leaving the bottom portion of the bag under the substrate in the tray. This makes for super easy cleanup after the last flush.
agar When I plan to inject a bag. I simply place a piece of heavy duty Scotch brand packing tape over the spot I plan to inject, to reinforce it. Then inject straight through the center of the tape, into the bag. Once injected, I place another piece of the same size tape over the injection site hole, to seal it. Works for me. But, I don't use normal filter patch bags - either.
Blue Helix Agar, those bags are super cool! If you can make your own filter, I heard from you that you can buy the plain bags for about a dime, making using spawn bags even cheaper.
mycofile, I have heard and even use sideways incubation sometimes. Ironically, I have some Goliath Pan Cyans incubating in this orientation now. Here's a picture showing them near completion.