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EZRider
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Dry conditions--Miracle Gro perlite the culprit?
#12552953 - 05/13/10 12:31 AM (14 years, 8 months ago) |
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The situation: Five PF cakes, birthed three days ago, in a shotgun terrarium. Terrarium is full of 1/4" holes on all six sides; most are 1 to 1.5 inches away from the adjacent holes. Two 23-watt, 100-watt-equivalent, 6500K CFLs shine five feet directly above on a 12/12 cycle. A fan sits on the floor, constantly blowing on "high," but not directly at the terrarium. The terrarium, rather than sitting on a table, is propped on opposite sides by two chairs facing each other, to ensure that air flows underneath as easily as possible.
I have no psychrometer as yet (and btw, I won't be bothering with any other kind of hygrometer--thanks for the heads-up, Hyphae!), but I can say that except for the perlite itself, the terrarium always looks and feels quite dry when it comes time to mist and fan. No way it's 90%+ humidity in there. Humidity outside the terrarium hovers around 50%, if the ancient analog hygrometer that just happens to be hanging on the wall in my house can be trusted. I never get static-electric shocks.
I suspect that the dryness may be caused by the Miracle Gro perlite I'm using, which is so fine and dusty that it seems to have plugged up the holes on the bottom of the FC. (At least, when I get underneath my FC and look up at the bottom, wet perlite sags through the holes.) If the bottom holes were plugged, you'd expect the situation I'm observing, wouldn't you? Humidification via wet perlite wouldn't occur, or at least would be seriously impeded, because air wouldn't be allowed to rise from below the terrarium due to the pressure differential, as it's supposed to. Would switching to coarser perlite solve this problem? (I want to get away from Miracle Gro anyway, due to the non-myco-friendly stuff that's in it.)
I realize that bigger pieces of perlite will provide less surface area, and will therefore hold less water, but that's a compromise I think I'll be willing to make. If necessary, I'll just switch out or resoak the perlite more often. I'd much rather err on the side of greater FAE from underneath the terrarium. What do you think?
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Mystery420


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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: EZRider]
#12552981 - 05/13/10 12:36 AM (14 years, 8 months ago) |
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get some pics up
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13shrooms
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: Mystery420]
#12553157 - 05/13/10 01:12 AM (14 years, 8 months ago) |
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I use the same MGP for my shotgunFC without issues.
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CoreyRubble
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: 13shrooms]
#12553311 - 05/13/10 01:43 AM (14 years, 8 months ago) |
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turn that fan off.. thats what is drying your shit out... your fan is blowing all the humidity out of your FC.
Perlite isn't constanly blowing moisture up.. it is evaporating off of it. you turning the fan on while giving great FAE is killing your RH. just mist and fan like everyone else does. It is fun and i am sure you will feel more of a sense of accomplishment
-------------------- fuck it im too high
tryin to find loopholes and shit...
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EZRider
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: CoreyRubble]
#12553514 - 05/13/10 02:53 AM (14 years, 8 months ago) |
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I just found this thread in which RR affirms that big pieces of perlite are better than small ones for water evaporation. I'll try switching and see if that fixes the problem.
CoreyRubble, I'm almost positive that RR said somewhere that you want some air circulation in the room. If I didn't run the fan, I wouldn't have any. Maybe I'll just turn it to low.
-------------------- Everybody wanna be some fat tycoon
Everybody wanna be on a tropic honeymoon
Nobody wanna sing a little bit out of tune
Or be the backbone of a rebel platoon
--Michael Franti and Spearhead, "Rock the Nation"
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TacoHerder
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: EZRider]
#12553583 - 05/13/10 03:27 AM (14 years, 8 months ago) |
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if your room has a air ven then that should be enough aire circulation.
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CoreyRubble
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: EZRider]
#12553988 - 05/13/10 07:40 AM (14 years, 8 months ago) |
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Quote:
EZRider said: I just found this thread in which RR affirms that big pieces of perlite are better than small ones for water evaporation. I'll try switching and see if that fixes the problem.
CoreyRubble, I'm almost positive that RR said somewhere that you want some air circulation in the room. If I didn't run the fan, I wouldn't have any. Maybe I'll just turn it to low.
You want a fan on in the room oscillating if you have a monotub.. if you keep a fan on at all times you will not be able to build up your humidity. having the fan on will push out all of your RH and the perlite will not be able to build it back up because there is constant air flowing through it
You could set your fan on a timer so it turns on for like 5-10 minutes every 2-3 hours. this will be sufficient.
Your just trying to get oxygen to your Myc not trying to see how they will hold up in hurricane conditions
-------------------- fuck it im too high
tryin to find loopholes and shit...
ill report back when my house is a mushroom
-just me-
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SomeGuy
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: CoreyRubble]
#12554006 - 05/13/10 07:51 AM (14 years, 8 months ago) |
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I've never had a fan and never had a problem. Also the holes at the bottom are to let co2 out, not let something in, thats why they are at the bottom I use miricle grow perlite on top of my pf's and in the chamber floor...no problems!
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Nyawinge



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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12555692 - 05/13/10 02:21 PM (14 years, 8 months ago) |
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Quote:
paducahovoids said: I've never had a fan and never had a problem. Also the holes at the bottom are to let co2 out, not let something in, thats why they are at the bottom;) I use miricle grow perlite on top of my pf's and in the chamber floor...no problems!
The holes at the bottom allow airflow over more of the pearlite layer. They aren't for Co2 exchange-that's why you fan.
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Fluffheads420
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: Nyawinge]
#12557392 - 05/13/10 07:16 PM (14 years, 8 months ago) |
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hey bro, i just began growing, and currently put my cakes/trays in my sgfc about 8 days ago and use the same perlite as you do and arent having any of them issues. i am not using any fan as mentioned nor any additional light other than a window and some natural light... hope it helps.
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SomeGuy
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: Nyawinge]
#12558422 - 05/13/10 09:23 PM (14 years, 8 months ago) |
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Quote:
Nyawinge said:
Quote:
paducahovoids said: I've never had a fan and never had a problem. Also the holes at the bottom are to let co2 out, not let something in, thats why they are at the bottom;) I use miricle grow perlite on top of my pf's and in the chamber floor...no problems!
The holes at the bottom allow airflow over more of the pearlite layer. They aren't for Co2 exchange-that's why you fan.
I got bad news...Your wrong. With co2 being heavier than air(a mixture of oxygen, co, co2 and others) and mushrooms producing co2, which falls to the bottom of the chamber, no air displaces the co2 upwards to come in. air goes out those holes. add an aquarium pump..goodbye fanning. All the co2, which falls to the bottom goes right out the holes. Unless you are pumping air into them air would never circulate up through the holes to an area thats "sealed". it's all about air pressure equalibrium
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CoreyRubble
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12558451 - 05/13/10 09:27 PM (14 years, 8 months ago) |
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ok you obviously need to read more about your hobby... you should make two fruiting chambers and try your little method with the pump. then try one with fanning.. i bet i know which one will work better
The holes on the bottom are there so air can come up through the perlite and create evaporation. That is what he means by it not being for FAE because you don't get FAE there is still a huge gas build up.
-------------------- fuck it im too high
tryin to find loopholes and shit...
ill report back when my house is a mushroom
-just me-
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prismism



Registered: 05/11/09
Posts: 5,570
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12558506 - 05/13/10 09:33 PM (14 years, 8 months ago) |
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Air is pulled in from the bottom of the chamber and through the perlite. The shotgun terrarium is a miniature weather system. The cooler air within the damp perlite is slightly more dense than the warmer air above, causing air to flow upward towards lower pressure, regardless of temperature. This airflow results in evaporative cooling within the perlite, perpetuating the flow as long as the air above is at a slightly lower pressure.
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SomeGuy
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: prismism]
#12558565 - 05/13/10 09:40 PM (14 years, 8 months ago) |
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Come on more dense air flows up? In that case the air is more dense than the air outside the chamber and moves out...the holes. Air with a higher relative humidity and therefor weight defies gravity and moves up? Ever take physics? The Earth orbits the sun
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Spongiform
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12558848 - 05/13/10 10:21 PM (14 years, 8 months ago) |
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Quote:
paducahovoids said: Come on more dense air flows up? In that case the air is more dense than the air outside the chamber and moves out...the holes. Air with a higher relative humidity and therefor weight defies gravity and moves up? Ever take physics? The Earth orbits the sun
He's right. The humidified air creates a micro pressure difference which draws air in through the bottom and out the top/sides providing a very very slight, but constant flow of fresh humidified air over the cakes.
Misting replaces the moisture lost from both the cakes and the perlite.
Here's some info better worded then I could:
Quote:
It's not just about the specific gravity of moisture vs air and CO2. The air in a properly functioning terrarium is never still. By moving, it mixes. There's not a nice neat layer of CO2 on the bottom waiting to drain out. That's not how it works. In fact, most of the CO2 exits through the holes in the top.
Remember, the heat of the cakes, however slight causes convection. During the day when a light is on, there is a slight heating. When air passes through the perlite, there's an evaporative cooling effect. All of this works together in a shotgun terrarium to provide a turbulent environment with fresh air constantly circulating for the mushrooms.
It's also common for new growers to overestimate the importance of humidity. We want a high humidity of course, but just as important, we also want lots of fresh air, which is the number 1 pinning trigger. The perlite provides the moisture for humidity, the holes provide the fresh air, and misting replenishes the moisture that evaporates from the cakes. Try to add to one of those three factors at the expense of the other two, and performance drops. RR
And right off RR's website:
Quote:
Shotgun Terrarium Theory of Operation
The theory of operation for the shotgun mushroom fruiting chamber is that natural air currents travel from areas of high pressure to areas of low pressure. Cool air has the molecules closer together than warm air, thus cool air is at a slightly higher pressure than warm air. When we put several inches of damp perlite in the bottom of our terrarium, we create an area with a slightly cooler temperature than the air above, which is exposed to lights that create heat, and our mushroom substrates, which are often at up to a few degrees warmer than the surrounding air due to thermogenesis.
This temperature differential, however slight, results in enough of a pressure gradient that it causes air to flow up through the perlite, absorbing moisture as it travels, and into the relatively lower pressure air within the fruiting portion of our fruiting chamber. This air then exits through the holes in the upper section of the terrarium, carrying the excessive CO2 produced by our mycelium out with it. With this design, no electrical or mechanical equipment is required. Regular misting helps to keep our brf cakes or other substrates moist, and also serves to replace the moisture that evaporates from the perlite.
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13shrooms
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: Spongiform]
#12558914 - 05/13/10 10:31 PM (14 years, 8 months ago) |
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--------------------
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RogerRabbit
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12558999 - 05/13/10 10:45 PM (14 years, 8 months ago) |
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Quote:
paducahovoids said: I got bad news...Your wrong. With co2 being heavier than air(a mixture of oxygen, co, co2 and others) and mushrooms producing co2, which falls to the bottom of the chamber, no air displaces the co2 upwards to come in. air goes out those holes.
No, it doesn't. CO2 is only slightly heavier than air and mixes thoroughly with it. Thus, the air has a higher CO2 level, but the gas doesn't remain separate and fall to the bottom.
With a shotgun terrarium, the primary flow of air is from the bottom under the perlite, up through the perlite and into the terrarium. This air mixes with the higher CO2 air in the terrarium, which escapes out the sides due to natural circulation. In addition to CO2, mushrooms produce heat, and the tendency of heat is to rise. The lights also produce some greenhouse-effect heating in the terrarium, relative to outside, resulting in more air flow. I've tested and measured this circulation pattern with a CO2 detector many times. The CO2 level is lower under the terrarium than it is beside it.
To the OP. You're not supposed to be running a fan in the room. Normal room circulation is plenty, especially if you keep a window cracked slightly open, as you should anyway for fresh air. Large perlite is also better than small. It's not about how much water the perlite can hold, but how much it can evaporate. The air spaces between large perlite allow for better evaporation. RR
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13shrooms
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: RogerRabbit]
#12559051 - 05/13/10 10:53 PM (14 years, 8 months ago) |
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Quote:
Large perlite is also better than small. It's not about how much water the perlite can hold, but how much it can evaporate. The air spaces between large perlite allow for better evaporation. RR
I thought the surface area was key for lasting humidity? so its just better to manually keep misting the perlite?
thats different from what you told me a year ago...good thing I switched to bulk.
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RogerRabbit
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: SomeGuy]
#12559073 - 05/13/10 10:57 PM (14 years, 8 months ago) |
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Quote:
paducahovoids said: Come on more dense air flows up? In that case the air is more dense than the air outside the chamber and moves out...the holes. Air with a higher relative humidity and therefor weight defies gravity and moves up? Ever take physics? The Earth orbits the sun
Yes, lots of us around here have taken physics, so we know that humid air is LESS dense than dry air. That's why clouds usually float above us. The heaviest air is when a cold wind brings an arctic cold front. They're usually right on the surface, and if you go up a few hundred feet, it can be ten to fifteen degrees warmer.
Dense air pushes on less dense air. This is how an airplane wing works. The air passing over the curved surface on the top of the wing has farther to travel, thus the molecules spread out and the air becomes less dense. The air flowing under the relatively flat surface of the bottom of the wing has less distance to travel, thus the molecules are closer together. This results in lift, with the bottom of the wing supporting the entire weight of the aircraft, provided it keeps its speed up. RR
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SomeGuy
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Re: Dry conditions--Miracle Gro perlite the culprit? [Re: Spongiform]
#12560617 - 05/14/10 07:31 AM (14 years, 8 months ago) |
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Quote:
Spongiform said:
Quote:
paducahovoids said: Come on more dense air flows up? In that case the air is more dense than the air outside the chamber and moves out...the holes. Air with a higher relative humidity and therefor weight defies gravity and moves up? Ever take physics? The Earth orbits the sun
He's right. The humidified air creates a micro pressure difference which draws air in through the bottom and out the top/sides providing a very very slight, but constant flow of fresh humidified air over the cakes.
Misting replaces the moisture lost from both the cakes and the perlite.
Here's some info better worded then I could:
Quote:
It's not just about the specific gravity of moisture vs air and CO2. The air in a properly functioning terrarium is never still. By moving, it mixes. There's not a nice neat layer of CO2 on the bottom waiting to drain out. That's not how it works. In fact, most of the CO2 exits through the holes in the top.
Remember, the heat of the cakes, however slight causes convection. During the day when a light is on, there is a slight heating. When air passes through the perlite, there's an evaporative cooling effect. All of this works together in a shotgun terrarium to provide a turbulent environment with fresh air constantly circulating for the mushrooms.
It's also common for new growers to overestimate the importance of humidity. We want a high humidity of course, but just as important, we also want lots of fresh air, which is the number 1 pinning trigger. The perlite provides the moisture for humidity, the holes provide the fresh air, and misting replenishes the moisture that evaporates from the cakes. Try to add to one of those three factors at the expense of the other two, and performance drops. RR
And right off RR's website:
Quote:
Shotgun Terrarium Theory of Operation
The theory of operation for the shotgun mushroom fruiting chamber is that natural air currents travel from areas of high pressure to areas of low pressure. Cool air has the molecules closer together than warm air, thus cool air is at a slightly higher pressure than warm air. When we put several inches of damp perlite in the bottom of our terrarium, we create an area with a slightly cooler temperature than the air above, which is exposed to lights that create heat, and our mushroom substrates, which are often at up to a few degrees warmer than the surrounding air due to thermogenesis.
This temperature differential, however slight, results in enough of a pressure gradient that it causes air to flow up through the perlite, absorbing moisture as it travels, and into the relatively lower pressure air within the fruiting portion of our fruiting chamber. This air then exits through the holes in the upper section of the terrarium, carrying the excessive CO2 produced by our mycelium out with it. With this design, no electrical or mechanical equipment is required. Regular misting helps to keep our brf cakes or other substrates moist, and also serves to replace the moisture that evaporates from the perlite.
Rogerrabbit, you're the man and you certainly know more than me, but this says colder air has higher pressure....I looked it up. Pressure goes UP one psi for every 10 degrees farenhiet. Put a ballon in the freezer and watch it deflate. Cold air is more dense and therefor has LOWER pressure. You ever see something work and then made a theory to explain it? I think you have. I'll take your word on the shotgun, I don't use one. I have an aquarium pump, so air obviously goes out my bottom holes. I suceed Oh powerful moderator
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