Grains usually contain higher loads of bacterial endospores which are very hardy and which survive the temperature of boiling water, therefore a normal cooking process can't kill them. A pressure cooker is required, since the temperature in a pressure cooker is high enough to destroy the endospores. Another, more time consuming method is the fractional sterilization. In this case, the jars fitted with a filter or a polyfil lid filter are boiled or steamed 212?F (100?C) for 30 min in a covered pot, three days in a row. Between the boiling steps the jars are best kept warm, around 30?C, to allow the remaining spores to germinate. The basic principle behind this method is that any resistant spores should germinate after the first heating and therefore be susceptible to killing during the second and third heating.

Mushrooms are not plants, so they do not require the type and amount of light to grow like plants do. Colonizing substrate should be kept in a dark place to make sure the substrate doesn't pin prematurely. Fully colonized substrate should be introduced to light to initiate pinning - light "tells" the substrate that the conditions are right for forming fruit bodies. (light is only one of the factors though, the others are lack of uncolonized substrate, drop in temperature and lower CO2 levels.
Different types of mushrooms require different light levels. Specific light level for the type you want to grow can be found in most good cultivation books.
A source with a wide spectrum of light, especially containing lots of bluish light (natural daylight or white fluorescent lights are very good examples of light with lots of blue) is best, depending on the types of mushrooms grown.

Grain(particularly rye and wheat) carry high loads of bacterial endospores.
If one experiences bacterial contamination problems the grain can be left to soak overnight (up to 24 hours) before pressure cooking to allow bacterial endospores to hatch.
If you let it soak too long, the grain itself will eventually start to germinate, which is not desirable. This can particularly be the case, if the temperature at which the jars are left is high, for instance in the summer. In this case it?s better to reduce the soaking time to around 12 hours.

The 3 most important aspects of grain preparation are to achieve an uniform, correct water content, to kill all contaminants and to get a shakeable substrate.

There are 2 main approaches to grain preparation:

Method 1.) Rinse the grain several times under flowing water and simmer it until the grains are soaked and begin to explode. With rye the simmer time is around 45 minutes, with millet or millet based birdseed around 30 minutes(but it strongly depends on the individual brand) Then strain the cooked grain for 20 minutes, fill in jars, screw on a lid fitted with a filter and pressure cook for 1 hour.

Method 2.) Fill the jars directly with the proper amounts of grain and water and pressure cook for 1 hour. If one experiences bacterial contamination problems the grain can be left to soak up to 24 hours before pressure cooking to allow bacterial endospores to germinate.

Basic rye recipe for 1 pint jar:

- 100g(3.5 oz ~ 125 ml) rye
- 110g(3.9 oz =110 ml) water
- knife tip full of gypsum


Basic millet or birdseed recipe for 1 pint jar:

- 100g(3.5 oz ~ 140 ml) birdseed
- 80g(2.8 oz = 80 ml) water
- knife tip full of gypsum


If you are going to prepare rye for producing spawn, you might use a tad less water( I use 105g in that case)

Fill into the jar, screw the lid fitted with a polyfill filter or a filter disc on the jar and pressure cook for 1 hour. Immediately after the pressure has settled, using protective oven mitts or a towel, take the still burning hot jars from the cooker and shake them well to mix the more wet and drier kernels.

The water retaining capacity can vary depending on the grain quality, the type and size of the pressure cooker and on sterilization time. The goal is to achieve the highest possible water content without alowing to many grain kernels to explode and without producing a soggy substrate. It's best to make a batch of test jars when one acquires a new grain for instance 100g rye and 100, 105, 110, 115 and 120g water. Then you'll see which water content provides the best result for you.

Which one of the 2 methods is better? It's mainly a mattter of personal preference, try both and see what works for you.

When you prepare whole grain jars, it?s good to shake them after the pressure cooking while they are still hot to redistribute the wetter and drier kernels.

After the inoculation:.

First time you shake the jars immediately after the inoculation.
The second shake should occur once the colonization is visible at around 5-10% of the jar surface.
A third shake can be made after the mycelium is visible at around 50% of the jar surface.


More shaking doesn?t always mean faster colonization, so don?t overdo it.

There are several reasons for this. Dung and straw are used as so called bulk substrates. This means you are usually working with a greater quantity of those substrates and inoculate it with grain spawn.

The second, probably more important reason is the contamination risk of sterilized substrates.

When you pasteurize substrates at 160-170?F (71-77?C) some beneficial micro organisms, mainly bacteria, stay alive, inhabit the substrate and ?guard? it against other more aggressive micro organisms. Mushroom mycelium is still able to grow on this substrate though.
This is the reason why you can inoculate bulk substrates with spawn in open spaces without taking special sterile precautions.
If you sterilize the bulk substrate it becomes as much susceptible to contaminants as for instance rye grain or whole rice. This means that you would have to inoculate the big amount of bulk substrate in sterile conditions, in front of a HEPA hood. And this is not practicable if you have big amounts of the substrate.

The above is only true for pure dung and straw, the only allowed additives are gypsum and calcium carbonate( for pH correction and stabilization).
As soon you add a additive high in nutrients to the substrate, for instance brown rice flour or wheat bran, the substrate must be sterilized and inoculated in sterile conditions.

The term "casing" as it is used in the mushroom cultivation is the method by which substrate is crumbled into smaller pieces, and covered with a non -nutritive layer such as peat, vermiculite, coco coir and different mixtures with additives.

Fill the colonized substrate in a opaque casing container, level it with a clean spoon or fork and spoon the casing material on the top of it as even as possible, without pressing it down.
Don't try to create a completely flat surface, small valeys in the casing surface are beneficial and necessary for primordia formation.
The thickness of the casing layer should relate to the depth of the substrate layer ( deeper substrate layer -> thicker casing)
It should be around 1/4th of the substrate depth. So if your substrate is 4 inches deep, the casing should be around 1 inch thick with a limit at somewhere 2 inches. So even if your substrate layer is thicker than 8 inches, a casing layer thicker than 2 inches is usually not applied.

Overlay is a term that refers to the condition which can occur to an overly colonized casing layer. A casing layer which has approached 100% colonization risks overlay. Overlay occurs when the fine strands of mycelia die and become hard and matted (as compared to the light, strandy mycelia you will become familiar with.) Overlay is often bright white, since it has become so matted and impenetrable. Mushrooms will NOT grow from overlay, as the mycelia layer is dead on top, and cannot be penetrated from below. Touching overlay (its generally not a good idea to touch casings) - it literally feels like it is one solid piece, as compared to the much more pliant healthy mycelia. Avoid overlay by initiating pinning at the proper time. Overlay can't be "cured," per se, since the top layer of mycelia is literally dead. But you can help a casing which has overlay by "scratching" it - by dragging a fork, knife, or any other tool which will till the colonized substrate and allow for new colonization. This is to be avoided at all costs for the following reasons. First, it's never advisable to touch the casing layer in any way. It simply opens up another route for contamination to set in. If you scratch, make sure your tools are sterilized (alcohol, boiling, etc.) and you are clean. But do not touch the exposed substrate with your hands, for any reason. Second, dealing with overlay means you're not producing efficiently: when you scratch the casing, the mycelia has to recover from the shock and also re -colonize the casing layer, setting you back at least an appreciable week.

Casings will oftentimes "shrink" during the course of colonization, and will often do so towards the end of a flush. This has 2 main reasons: Growing mycelium converts the nutrients in the substrate to mycelium, heat and CO2. It has been established that an oyster mycelium converts up to 50% of the substrate to energy and mushrooms during its lifetime. This substrate is then "gone", that's why the substrate amount is getting less over the time. The second reason is the substrate pulling its water resources together and providing it for the fruiting stage. If, for example, 100 grams of fresh fruit are picked from a casing layer, that means the casing has lost at least 90 grams of water to the fruiting stage. The loss of water is evinced by the "pulling". A pulling -away casing can often be easily rectified after a flush is harvested: simply by adding more casing material to the sides where it has pulled, patched any casing layer that may have been pulled up when you harvested (on the ends of the stems), and mist with water. The key is to always provide the casing layer with water by misting it so it stays moist, but it shouldn't be wet. Water is key to the hobby, but too much can drown!

The contaminants are so named solely because they are undesired. If one were trying to culture Penicillium and spores of a Psilocybe settled onto the agar media and germinated, the resulting mycelia would be the so-called "contaminant." The contaminants in mushroom culture, however, are primarily molds, bacteria, viruses and insects. The pathway by which a disease is introduced, known as the vector of contamination, can be used to trace the contaminant back to its site of origin using simple deduction. By observing how a contaminant affects the mushroom crop and by carefully noting the conditions in which it flourishes, a cultivator can soon identify its cause.

The five most probable vectors of contamination are:

1. the cultivator.
2. the air.
3. the substrate to be inoculated.
4. the spores or mycelium that was being transferred.
5. the inoculating tools, equipment, containers, facilities, etc.

Different contaminants are associated with different stages of mushroom cultivation. Contaminants in agar culture most often come from airborne spores. Grain cultures contaminate from airborne spores and from a source which many cultivators fail to identify: the grain used in spawn making which is laden with spores of imperfect fungi, yeasts and bacteria.

Molds and bacteria do not grow well in a climate specifically adjusted for mushrooms. Although both mushrooms and contaminants prefer humid conditions, the latter thrive in prolonged stagnant air environments whereas mushrooms do not. The differences are frequently subtle?amounting to only a few percentage points in relative humidity and slight adjustments to the air intake dampers in the growing room.

The contaminants can be divided into two well defined groups. Those attacking the mushrooms are called pathogens while those competing for the substrate are labeled indicators or competitors. (Mushroom pathogens are either molds, bacteria, viruses or pests; indicators are always fungi of some sort). In general, mushroom pathogens are not as numerous as the competitor molds, though they can be much more devastating.