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Growing mushrooms at home - beginner's experience


Technology, biology, chemistry and natural sciences in general are becoming more and more accessible by people with even modest incomes. The upshot is a multitude of projects carried out by creative people around the world, each of them unique and interesting to follow via Internet. That's what I like to do in my spare time - anything out of that diversity might ignite a spark and captivate me.
The latest addition to an already wide range of interests I have is biology. But how to segue from a background of IT and electronics to one of the most complex fields there are out there? You have to start small, that's for sure. Eventually, I think I found an optimal way to do that for an average layman like me.

I was fascinated with Thought emporium's video here:

and decided to give growing mushrooms a try. Why use it as a gateway to biology?
  • It gives you tangible (and even edible) results.
  • It's easy to to at home, without any specialized equipment (well, autoclave/pressure cooker is probably a bit of a stretch to this statement, but we'll find a way to do without it for starters).

What this post is about

Although the learning curve can't be called too steep (look at how Justin lays it out in video above! 1-2-3 and you have your mushroom jars ready to get colonized), I'd say there's still a multitude of pitfalls people should know of, even in the very beginning.

I'll attempt to paint a bigger picture on growing mushrooms at home, giving an overview of each possible option to do each step.

This post is a summary of what I found while trying to grow my first batch of edible mushrooms, including the specific guidelines and my experience in growing Shiitake mushrooms (no autoclave/pressure cooker used, inoculation with grain spawn instead of syringe). I deviated quite a bit from the standard practices when growing , so I thought the results can be of interest to someone else.


  • Fungi - a whole kingdom of living organisms that includes ordinary mushrooms that we know and love alongside with mold and yeast infection. In most contexts it's just synonymous with the word "mushrooms" - unless we're speaking advanced biological experiments.
  • Spores - fungal seeds. This is how mushrooms reproduce. Applied to mushroom growing, they mostly come in the form of syringe filled with water-spore mix.
  • Mycelium - mushroom "roots", white and fluffy stringy substance.
  • Tek - technology, i.e. specific guidelines you follow to attain some goal (most commonly, grow mushrooms)

How to grow mushrooms at home

The most widespread tek used to grow mushrooms at home is called PF-Tek. Any manual on growing shrooms at home you'll find online is likely to be a modification (they are sometimes generically referred to as BRF cakes tek) or even carbon copy of the original PF-Tek conceived in 1992 by Robert McPherson (Psylocybe Fanaticus). As you must have guessed already, it was used to grow magic mushrooms, but in fact it's a versatile technique that will accomodate any type of mushrooms.

So why does virtually everyone use PF-Tek now?
  • It's approachable with tools and ingredients that average person either has in their home already, or can buy in the nearest convenience store. 
  • Simplicity of scaling - if you want more mushrooms, you just mix more substrate and fill more jars. Nothing fancy here.

PF-Tek in a nutshell:
  1. You fill some canning jars with substrate of Brown Rice Flour (BRF) mixed with vermiculite,
  2. You sterilize those jars in pressure cooker to give mycelium headstart in growing (otherwise mold will colonize your rich in nutrients substrate quicker)
  3. You inoculate them (i.e. shoot a syringe of mushroom spores inside) and just let mycelium colonize the jars. No sterile environment needed (and it's a huge plus for amateur growers!) as the spores or mycelium are injected through the port in a jar, i.e. jars don't have to be opened and no airborne contaminants have the chance to get in.
  4. When the jars' content turn completely white, it's time to dump the "cakes" out of their jars and let mushrooms sprout. 

These basic steps will apply to any tek where jars/drinking glasses are involved. Alas, there were some reasons why I could not apply PF-Tek in its original form:
  1. It requires pressure cooker or autoclave to sterilize the jars.
      Now, all fungi enthusiasts will urge you to pony up and buy a used pressure cooker, and rightly so - the most common case of failure in the process of growing mushrooms is having mold colonize your substrate before mycelium does. Boiling the jars at elevated pressure is the best way to kill off the germs inside it.
      But what if this mushroom hobby doesn't take off? I didn't want another bulky gizmo gathering dust in my closet after deciding that this hobby is not for me. The most natural way to get into mycology seems to find a way to grow your first couple of batches with a barebones setup, and add equipment as I go.
  2. Your spores have to be packed in syringe.
      In PF-Tek, you flame sterilize the needle and inject the spores directly through the sealed top of your jar, avoiding contamination this way.
      What I incidentally bought was a ziplock of colonized grain. To inoculate a jar with it, you'd need to crack the lid of a jar, and doing that will surely result in airborne spores infiltrating the substrate.
  3. This one is a bit silly, but I couldn't find polyfill to stuff it into the jar lid - I'm using something that is simpler to procure where I live at the moment.

Like you just saw, the process of growing mushrooms is divided into several cleanly-defined steps. Each of those can be performed differently depending on the level of your investment in mycology hobby and your experience.

What's important is that EACH of them CAN be done no matter how much tools/experience you have, the key is understanding what you're trying to accomplish at all times.

We'll concentrate on the easiest/cheapest ways to do each step, although I'll also briefly describe other methods and give some links to read up on them, for future reference.

I really recommend reading (or at least skimming through) at least one of the links below: those are PF-tek writeups that helped me most.

PF-Tek original guide
PF-Tek laid out simpler
One more good guide - EvilMushroom666's Take on BRF Cakes
Yet another good guide - Easy BRF Cakes Mushroom Growing Method
The author tried to collect all possible info for beginners here
Lots of guides for every occasion

Steps + approximate timeline

Before attempting to grow your first batch, try to find some guidelines for the specific mushroom you're trying to grow - this didn't occur to me at first, but many aspects of growing Shiitake are different from the more common mushrooms like Portobello and Oysters. For instance, I found out that Shiitake take much longer to colonize their substrate, and require cold shock as a trigger to start fruiting.

Here are some good highlights of Shiitake cultivation
About Lentinula edodes (Shiitake)
Shiitake BRF Growlog - Many Large Pictures

Materials preparation

Takes: about 30 minutes.

It just involves preparing your jars, making a still air box (if needed) and a fruiting chamber (always needed).

Mycelium in a jar needs oxygen to breathe (yes, just like animals it breathes oxygen and exhales carbon dioxide). At the same time, the contents of the jars are supposed to be sterile (or at least without too much contaminants), and we can't just leave them open because of that. PF-Tek makes use of polyfill (or pillow fluff outside US) as the material to let mushrooms breathe while keeping the germs out:

Polyfill isn't readily available where I currently reside, and buying a pillow just to rip it apart seemed a bit excessive, so I was forced to improvise - in fact, any synthetic "breathing" material will do, polyester for example.

Still air box can be omitted if you bought spores in a syringe - we'll get deeper into this later.

Fruiting chamber is the place where you'll actually grow the end result of your endeavor: fruits aka mushrooms. This is the last phase so you can actually start preparing your fruiting chamber during the colonization phase, since it mostly entails just waiting.

Substrate preparation

Takes: anywhere from 5 to 30 minutes depending on substrate in question.

You can grow mushrooms on a wide variety of substrates: some more popular like brown rice flour + vermiculite, wood chips, sawdust and bird seed;  some more exotic like popcorn, cardboard or coffee grounds.

In fact, mushrooms will thrive on almost anything you throw them into - what seems to be the common denominator about this assortment of materials is that it's all plant-derived substance that has to be hydrated and full of nutrition.

Choosing your substrate will depend on the fungi you're trying to grow - look up its name and see which substrates it prefers. Here's some links to give you a broader picture:

List of wood-loving species
List of dung-loving species
Some more substrates and fungi that love them


Fractional sterilization: 3 days and 3 hours.
Pressure cooking: about an hour.

Some substrates will be more nutritious than others, hence lucrative for other kinds of fungi - like mold. We don't want to grow mold, so depending on your substrate you'll either want to pasteurize or sterilize it.

Pasteurization is just a reduction of the number of germs in the substance: for instance, the milk you're buying in a store is pasteurized. Pasterization usually involves bringing the substance to moderate temperatures not exceeding 100°C (212 °F). Sterilization, on the other hand, attempts to eradicate all living organisms inside your jar.

You can read up more on sterilization vs pasteurization here.

Jars, or rather the substrates they usually throw into them,  have to be sterilized, and usually people use pressure cookers to attain extreme conditions that will kill off any life inside them. I'm using another method: fractional sterilization.  Unlike pressure cooking, it can be accomplished using only commodity kitchenware. Fractional sterilization is 3 hour-long boils of your jars spaced 24 hours apart.

Details about fractional sterilization are here.


Takes: 1 to 2 hours.

Inoculation is the process of adding spores to the sterilized/pasteurized substrate.

If your spores came in the form of a syringe - you're in luck! Just add an extra hole to the jar lid, smear it with epoxy or silicon adhesive - this is going to be a dedicated "port" for spore delivery - and you can inoculate in open air. Flame-sterilize the needle and inject it into the "port" to knock up the jar without any nasty contams hitching a ride.

If your spores came as a grain spawn, you'll need some kind of germ-free environment to dispatch it to a jar. Average household's air holds a multitude of mold spores, and doing inoculation in open air is likely to contaminate your jars.

The easiest way to establish the germ-free environment is a Still Air Box which I'll be using for inoculation. It's also built from the stuff you can get from your local supermarket.

Further reads:
Overview of different disinfection options
Building a laminar flow hood - more advanved and involved piece of technology for having the clean air during inoculation.

Colonization/Incubation and Consolidation

Colonization/Incubation: 4-5 weeks.
Consolidation: 1 week.

Colonization refers to a process when the fungus grows its mycelium out in all direction and eventually takes up all the substrate. This will be visible to the naked eye: when the jar turns completely white the colonization is complete. When the colonization is finished, fungus can fully utilize the substrate (i.e. extract nutrients from it).

If you grow your mushrooms at home temperature, you don't need any additional heating. Incubation is assistance in colonization if you decide to store the jars in less favorable conditions.

Consolidation starts after the colonization is complete - the substrate's turned all white and fluffy, and you just need to give it one more week to let mycelium make use of it. In time, substrate should start developing pins, that is, small colored aggregations of mycelium. As soon as the pins have emerged, it's time to "birth the cakes", or dump the substrate out of jars.


Takes: 1-2 weeks

Fruiting is just an appearance of fruiting bodies - what people normally call "mushrooms". It takes place in a fruiting chamber - a container with high humidity maintained inside.

This phase starts when colonized substrate is dumped into the fruiting chamber, with an optional step of rehydrating it beforehand (it's called dunk and roll). All the grower needs to do from now on is to keep an eye on the chamber - the air inside should be fresh (oxygenated) and humid at all times. There's lots of fruiting chamber builds out there, but the most popular and easy to build seems to be Shotgun Fruiting Chamber (SGFC) - just a plastic container with holes in it (named so because hole pattern looks like it's been shot at with shotgun) with perlite in it to hold water and maintain humidity.

SGFC build

The mushrooms will be ready to get harvested in a week or two. Cut them off when mushroom's caps start to curve upwards. And that's it, really.

What I've used

Most of it (except spores maybe) can be sourced from local hypermarkets like Auchan, Castorama and Leroy Merlin.

* Spores (as grain spawn or syringe - syringe is preferable and you'll see why below in this list)

What I got. What I should've gotten.

* Transparent jars (glass or plastic) with wide mouth (i.e. the rim should be either the same width or the wider than the rest of jar's body). If you can't find jars like this it's not a deal breaker - it's just going to be a pain to get the colonized substrate out of them. You can either keep the substrate in the jar (results in lower yield) or have a hard time getting it out. 😊

Leftover jars from canned meat just came in handy!

* Still air box (SAB) - for when you have something other than a spore syringe.

Ingredients for my SAB: clear plastic tote (container), 2 PVC flanges for plumbing.

* Something that can puncture the top of your jar. For example: handheld drill, nail and a hammer, a knife that you're willing to mess up when you attempt to pierce a metal lid with it, etc...

* Aluminum foil

* Some artificial fabric (polyester plaid, pillow fluff (polyfill) etc.) - should let mushrooms breathe, not letting contaminants it. Artificial cloths are resistant to decay when exposed to humidity.

I just bought the cheapest synthetic piece of cloth: note  the label saying 100% polyester.

* Large saucepan / soup tureen. To sterilize your jars.

* Rubber gloves. Any impenetrable gloves will do (not the garden variety)

* (Optional) 70% ethyl or isopropyl alcohol (this concentration works better than, say, 97% - to see here to learn why) - to disinfect stuff. You can use soapy water instead, I just opted for rubbing alcohol because it doesn't require any additional effort - just grab a bottle and pour on anything you want disinfected.
Ethanol with a funky violet hue - supposedly to keep undemanding alcoholics from drinking it.

* Some container where fruiting (i.e. mushrooms appearing) will happen. I just grabbed some buckets left over from construction works for free. Of course, they had to be thoroughly rinsed and aired to get rid of construction smell.

* Your substrate. Choose the kind of substrate which your particular mushrooms grow best on.
The mushrooms I'm trying to grow - Shiitake mushrooms - thrive on wood, therefore the best bet for substrate material is wood chips or sawdust.

Since it's kind of easy to obtain different kinds of substrate, I decided to try 4 variations of it and compare which works best and requires least effort:

* Variation 1. Brown rice flour + vermiculite.
      * Brown rice or brown rice flour (BRF). BRF is hard to obtain in some places so I just bought a           bag of brown rice and ground it manually.

Regular white rice, like in that container to the left,
is not going to cut it.
Store-bought brown rice,
ready to be ground into flour.

      * (Optional - if you couldn't find brown rice flour) Blender/coffee grinder. To crush the rice grains if you can't find BRF where you live.

      * Vermiculite - order online or use sawdust/wooden chips instead. The purpose of vermiculite is to hold water and make substrate more loose.

No luck finding vermiculite in garden shops where you live? Online delivery will save the day.

10L bag of vermiculite is more than enough for 50+ jars.

* Variation 2. Wild bird seed (WBS).
     * Bird seed, how much you'll need will depend on how many jars you want - you'll fill each of              your jars about halfway to the top.

* Variation 3. Coffee.
     *Coffee grounds. Many of us have a coffee machine at work or even at home:

These babies go through tons of coffee beans yearly, and after being ground and steamed, the beans just end up in landfills. We'll amend the situation slightly by reusing coffee grounds to grow fungi with. There's nothing tricky about the process of gathering those - just crack open the coffee machine, and you'll see those hockey puck-shaped grounds:

Fill your jar almost to the brim with them. You're all set!

* Variation 4. Cardboard.
     *Scraps of corrugated cardboard. Corrugated cardboard has more airy texture and is easier to colonize.

     *Any plastic or glass food container.

* Variation 5. Supplemented sawdust.
     * Sawdust. You don't even have to buy it - people have to saw timber all the time and byproducts are usually thrown away. Pay a visit to the nearest park/forest/sawmill and see what it has to offer you.

Full bag of sawdust I've gathered in a park nearby. Took me about 15 minutes, and this bag will fill many jars.

     * Supplementation. I threw in some brown rice flour left over from substrate 1 to add nutritional value to sawdust. Although I suspected that wasn't really necessary and prepared another jar with plain sawdust in it. It's going to be interesting to compare the growth rate of plain vs supplemented sawdust.

The process of growing mushrooms, applied

Materials preparation

As I mentioned above, we'll have to prep the jars to let mushrooms breathe. If you have polyfill (pillow fluff) for sale where you live - this page is for you. If not - let's proceed with making our makeshift jar filters!
  • Drill/poke the holes in the lids. Size does not matter much - some air exchange must take place through those.
Left to right: the good, the bad and the ugly.

  • Cut the synthetic cloth to scraps the size where they'll fit between the jar and the lid when it's screwed on.

  • This is what end result is supposed to look like:

Bad news for those who had their spores come as grain spawn - you'll have to construct a Still air box (SAB) to be able to inoculate the jars later on. SAB is just a huge container with two holes for hands that can be covered.

You can take a look at some example builds of SABs if you follow those links:
Still Air Box design/prototyping/theoryTL SAB tek, and another Still Air Box build.
  • Mark the holes.

  • Cut the holes - with red-hot nail/awl for instance.

That was it! Here's what ready SAB looks like:
Ready SAB with holes plugged.Back view of the front wall - the caps fit snugly in place.

Substrate preparation

* Variation 1. Brown rice flour + vermiculite

Refer to any of the PF-Tek links from the theory section, for example this one, to learn the proportions for mixing this substrate.
  • Load enough grains to cover the blades. Grinders can't handle more than that really well.

  • Grind the rice to a fine flour.

  • Fill about half of the jar with vermiculite.

  • Next step is mixing in water and rice flour. You can dump them into the same jar to make measuring easier, but I personally found that mixing process is easier to carry out in a bigger container:

Mix it all up until the substance is uniform. We want to aim for airy and well-hydrated substrate, so add more vermiculite/water if it looks too dry or clumpy.

Well-mixed BRF+vermiculite substrate.

  • Load the substrate back into the jars. Leave a finger's distance between jar lid and substrate (more than I have on the picture, actually, I should've left a finger's distance to the portion where thread starts)
BRF + vermiculite packed in the jar.
  • Close the jar, placing the synthetic cloth piece in between jar mouth and lid.
Finished product.

* Variation 2. Coffee.

 You don't need to prepare them, although supplementing them with sawdust would probably improve the quality. Adding vermiculite you obtained for the first substrate may also help if it looks too clumpy.

* Variation 3. Wild bird seed (WBS)
  • Add bird seed into the jar so as to fill about half of it.

  • Soak it overnight. You'll notice (even when you pour the water into the jar) most of the black sunflower seeds starting to float. Now, I've seen some teks suggest you should remove every one to the last of them from the substrate, but I didn't see any negative side-effect to leaving them in - they get colonized just fine.
Before soaking. After soaking.

  • The grain will swell and almost double in size after an overnight soak. What I did with black sunflower seeds was remove only the ones that were floating and could be disposed of by just effortlessly scooping through the top layer of water. 

  • Rinse the grain thoroughly under the strainer (collander) - there should not be any clumps and slime left.

  • Pack it into the jar and close the lid, performing the same trick with the piece of cloth.

* Variation 4. Cardboard.

Weird enough, none of the cardboard teks mention any sterilization or parterization. This is the reason I'm using just a plastic container to house mycelium-occupied cardboard pieces.

As to the reason why those simple precautions against mold are omitted - it remains to be found out. I ran one experimental batch just to see who gets to colonize cardboard first: mushrooms or mold.
  • Cut the cardboard to pieces that fit into the container.

  • Soak them in water for about 20 minutes until cardboard easily comes apart when you pull it. Top and bottom layers are flat, with corrugated layer in the middle.
Cardboard becomes more pliable after soaking. It separates into layers if you gently pry them apart.

  •  Out of those layers, we'll only need the corrugated one. Dump the pieces onto a surface. Now, since the pasterization/sterilization step is omitted, you can get straight to inoculation stage (with cardboard substrate only).

* Variation 5. Supplemented sawdust.

To compare the performance of supplemented vs plain sawdust, I'll show you how to prepare both kinds of sawdust substrate.
  • Measure out enough sawdust to fill your jar about 1cm (1/2 in) under the top. Even less than that for supplemented substrate, because the additives have to go somewhere too. 
This is the level we're aiming for. Make it lower for supplemented variant.
  • Fill the jar with water and leave the sawdust soak for 12h (or one night).
  • Strain the water. If you're making plain sawdust substrate, jump straight to the canning step.  Dump the moist sawdust into a bowl. Add your supplementation. You can't go wrong with the amount of flour, but I'd add about quarter to half of the sawdust volume.
  • Mix it up thoroughly.
  • Pack your jars with substrate, leaving about 1cm (1/2 in) at the top again. Don't tamp it down - it's got to have loose feeling to it.
  • Close the jar with filter lid.


Prerequisites:  all your jars are loaded with substrate and closed.

  • Put a tinfoil hat on each of the jars. This is to retain the moisture content of substrate during boiling.

  • The jars should be raised above the bottom of the saucepan - this will ensure they won't crack. Devise some sort of spacer - as you can see, I just intertwined 3 forks to make a stable structure. Gives about 1cm of headspace.

  • Heat the pan until it's close to boiling.

  • Carefully lower the jars into the saucepan. Now you can bring it to simmering boil.

  • Keep simmering under the lid for an hour.

  • Turn the heat off and let the whole thing cool down for some time - if you yank the jars out straight away they might crack due to temperature difference.

There's not much to tell about two remaining boils - they're spaced 24 hours apart as well, and after the last boil you have your jars sterilized. Time to launch some beneficial life into them!


* Variations 1 to 3 and 5: Substrate in jars.

I just prepared a short video to demonstrate how inoculation in a still air box works. This is one of the situations where one picture is worth a thousand words, that's why I made a POV style video of it. Things to keep in mind:
  • Still air box is about stillness of the air inside. It's nigh impossible to create a really sterile environment, so we're building an isolated space where every live organism or spore floating in the air eventually swoops down and sticks to the wet box sides due to absense of up-going currents in the air. Be really gentle with the way you move your hands.
  • It doesn't matter much what you wipe the walls with: soapy water, chlorine in water, disinfectant or alcohol. The point is to leave the surface slightly wet to trap the contaminants.
  • Try to keep the time when the jar is opened to a minimum - just crack the lid, throw in mycelium and quickly close it. The less time it spends open the less the chance of contamination.
  • It's entirely possible to inoculate jars with pieces of colonized cakes. I actually did that with sawdust-based substrates - by the time I decided to make some more jars with sawdust, my jar with wild bird seed was 100% colonized. When birthing the WBS jar, some colonized grain clumps naturally separated off of the cake and I simply gathered those, packed them into a ziplock and used it as inoculation material later, much in the same way I inoculated the jars with store-bought grain spawn.
  • Break your grain spawn up into pieces into small pieces (inside SAB, of course! Watch the video). Don't separate it too much - 2-3 grains will colonize much slower than a bigger clump. I found that moderately-sized pieces about half the size of a peanut work best.
Circled in red is the size I usually use for inoculation.

Make sure to wash your equipment after you're finished with inoculation.

Now that the jars are full of mycelium you can shake them to distribute the spawn evenly. Now it's time to put them away for a long time and give them time to grow through substrate.

* Variation 4: cardboard substrate.
Inoculation is done in open air (this is an experiment, remember?) and it's basically just laying layer after layer of corrugated pieces of cardboard while sprinkling some grain spawn in-between every now and then.
  • You should've separated the cardboard into 3 layers in substrate preparation stage.  Now you can discard all but the corrugated layer in the middle - it allows for better air exchange and gives enough space for mycelium to grow. Start laying the cardboard pieces in container while alternating patterns of corrugation for each consequent layer.

Horizontal stripes on the previous layer, vertical on that, and so on.

  • Drop a couple of pieces of grain spawn in some of the layers. Some of the pieces I have in the picture below are quite small - I recommend having 4-8 grains in one seedling.

  • Fill about  two thirds of the container and close it. Since this plastic container doesn't have anything for proper air exchange, open it up daily to let some fresh breath in. Because we did everything in open air from the start, it shouldn't affect the outcome.

Colonization/Incubation and Consolidation

Work in progress: use action camera to take timelapse of colonization and fruiting


To let fungi develop the fruiting body, we'll have to emulate the environment of the forest when the weather is prime for fruiting as close as possible. Here's what those boil down to:

  • High humidity - really damp, something approaching 80-100% RH will work for most species.
  • Warm temperatures. Room temp is fine, but if you have to fruit outside in the winter you'll have to think about some heating.
  • Indirect dim light. There's just a tiny amount of light coming down from the thick canopies above in forests, but it's still there. Complete dark is not desirable, just like intensive head-on lighting isn't.
Again, consulting with the "spec sheet" of your mushroom will give you every piece of information you need to achieve the perfect environment for fruiting.

The simplest and the most effective fruiting chamber people usually build is a shotgun fruiting chamber, which is simply a huge transparent container with holes in it sitting somewhere with not too much light.

What I decided to try out was make a similar chamber out of an opaque container. My expectation was that the holes will provide all the necessary dim light to mushrooms inside. I'll have to expose the chamber to bright light for this to be possible, instead of finding a spot with dim light in my apartment.

Here's the recipe for my opaque shotgun fruiting chamber:
  • Grab any opaque container big enough to house your cakes. I grabbed two 10-liter buckets left over from construction works nearby. You'll also need a drill fitted with bit any size from 4mm to 10mm (5/32 in to 13/32 in).
  • Start drilling holes on every side except bottom. You can follow any fancy pattern you wish or just drill holes randomly.
  • You also want to keep about 2-3cm (1in) from bottom hole-free as you'll be pouring moisture - retaining material there.

Inside view. Lids also have to look like Swiss cheese - fungi will get their dim light from these holes.
  • Drilling a plastic bucket will leave hole edges jagged. Shave them away with something sharp. Personally, an ordinary kitchen knife did the job for me. That's it, you're all set with your new fruiting chamber! 

Lessons learned

1) It really is important not to tamp down the substrate when packing it into the jar. The airier the substrate, the faster it will be colonized. I really over-compacted BRF substrate and it's clearly visible in colonization timelapse that it took forever to colonize, especially the bottom layers.
2) Work in progress.