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Offlineshroomey
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Shotgun terrarium modification: Introducing extra warmth & humidity
    #9725091 - 02/02/09 07:53 PM (15 years, 1 month ago)

Hi all,

I'm a first-time grower, with a couple of cases (ok, I admit - kit bags) currently being happily colonised in my brand-new TIT incubator...

But when it comes to the fruition stage, my problem is very low temperatures. It's freezing cold in the house (snowing outside it), about 54 (coldest) to 68 (warmest). Yep. I know. Old house, cold house...

I really like the shotgun terrarium design, but I'm still not very confident that the results that I'll get at these low temperatures will be anything to write home about...

And I've read in plenty of threads that a heating mat is probably not going to work...

So here's my idea: I was thinking that maybe I could modify the design a bit, like this:

1) Build a standard shotgun terrarium (the inner tub), with holes all around - including the bottom
2) Get another tube (outer), and fill it with a couple of inches of water
3) Throw a tank heater in there, cranked up to the max
4) Drill a two-inch strip of many-many holes on the outer tub, above the water level (for air inflow)
5) Place the inner tub inside the outer tub, with the bottom of the inner one a couple of inches above the water (so that the air inflow strip on the outer tub lies between the water level and the bottom of the inner tube)

Here's a (crappy) diagram:



The idea is that there will be a warm body of water and air underneath the inner tub, which will:

a) Provide some heat
b) Possibly increase the humidity in the inner tub, as the hot vapours rise from the water, through the bottom holes and perlite of the inner tube, and into the air inside

Does anyone have any thoughts on this design? My main concerns are:

1) Condensation. As I've read in various other posts elsewhere, heating a terrarium causes this problem. Do you think it will still be an issue even with the holes drilled on the inner tub, and the hot vapours rising up into the inner tub?
2) Contamination. I'm worried that the still, warm water between the tubs will provide an excellent environment for all sorts of undesirable guests... Perhaps the fact that the air will be constantly renewed solves this? Maybe some hydrogen peroxide in the water?

Cheers

Edited by shroomey (02/02/09 08:07 PM)

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OfflineBuckeye Oysters
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9725144 - 02/02/09 08:01 PM (15 years, 1 month ago)

That would probably work as long as their is some space between tubs for warm air to circulate up.  Drill as many holes in both tubs.  Peroxide is only good for controlling cobweb mold.  Use 2 tsp bleach per gal of water to control contams.

You dont want the water to rise above 77F, so be sure to test your aquarium heater.  That design probably would increase humidity coming into the tub, but that is not necessary.  You want the inside of the tub to be an evaporating environment and only have discrete introductions of moisture (misting) and periods of water evaporating, but never going dry.

Shrooms will fruit as low as mid 60's and make nice thick fruits, so you really don't lose out fruiting in cooler temps.  You figure in Florida it cools off to about that after rains come and mushies pop.


--------------------
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OfflineRogerRabbitM
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Buckeye Oysters]
    #9725263 - 02/02/09 08:17 PM (15 years, 1 month ago)

Not going to work.  If it's extremely cold, put your light a bit closer, or if necessary, place an incandescent lamp near the terrarium during the day for the extra heat. At night, it will be fine at your temps.  I wasn't suggesting an incandescent light bulb as your only source of light, but simply for the extra heat it will provide via the greenhouse effect.  Place your terrarium near a bright window and/or use fluorescent lamps for proper lighting.  You'll gain five degrees or so of warmth just from the lights, and that's all you need.
RR


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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Buckeye Oysters]
    #9725325 - 02/02/09 08:29 PM (15 years, 1 month ago)

Thanks for the reply.

What you say about discrete introductions of moisture (misting) is interesting. The reason I'm building this (besides the cold) is because I may be away periodically (up to three days), so I was looking for a way to keep things wet during my absence. Do you think that 2-3 days without misting is going to cause problems?

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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: RogerRabbit]
    #9725345 - 02/02/09 08:32 PM (15 years, 1 month ago)

Thanks for the advice. I'll try placing a lamp nearby and see if I can get the temperature to rise.

Out of curiosity, do you care to explain why the design would not work? Is it because of condensation, contamination, or something else that I forgot?

Thanks again

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OfflineRogerRabbitM
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9725878 - 02/02/09 09:53 PM (15 years, 1 month ago)

Quote:

Out of curiosity, do you care to explain why the design would not work?




Heat creates an area with the molecules farther apart, thus at lower pressure.  If the outer tub was heated, it would be the area of low pressure and the air would flow from the terrarium to the heated tub below, thus drying the air in your fruiting chamber.

The design of the shotgun terrarium is that the evaporative cooling effect of the damp perlite causes high pressure, which then causes air to flow into the relatively warmer air in the terrarium proper, which is at a lower pressure.  The pressure gradient is minimal, but enough to create natural air flow, which provides air exchange and humidity for your fruiting substrate.
RR


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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: RogerRabbit]
    #9726176 - 02/02/09 10:39 PM (15 years, 1 month ago)

As far as I know, pressure increases with heat (exactly because, like you said, the molecules push away from each other more), and thus air tends to flow from the hotter areas towards the colder - and this is why warm air always flows upwards, where the pressure is lower. Therefore, it seems to me that, in the design I propose, the air would flow upwards from the hotter outer tub towards the cooler inner one.

Am I missing something? Perhaps you are referring to CO2 (which tends to flow downwards)?

BTW I tried placing a 40 W incandescent lamp next to my (empty) terrarium as you suggested, and saw an increase in temperature of (you guess...) exactly 5 degrees! So it seems that I won't be needing the extra tank heater and tub after all - I'll stick to the setup you propose because it's cheaper and there's less hassle involved. However, do you think the bright light of the lamp (3 inches away, facing directly towards the terrarium from the side) will hurt the mushrooms?

I also wonder if skipping misting for 2-3 days will cause problems... What do you think?

Tomorrow I'm getting myself a hydrometer, see where I stand humidity-wise...

Thanks again for taking the trouble to help - really appreciated... :smile:

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InvisibleRoger Fudd
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9726193 - 02/02/09 10:42 PM (15 years, 1 month ago)

shroomery's right. That's the whole idea of a pressure cooker-the heat causes steam to pressurize the sealed container.

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Offlinepepprodigy
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Roger Fudd]
    #9726475 - 02/02/09 11:50 PM (15 years, 1 month ago)

Your both right, but in different set-ups. In a pressure cooker, the heat is rising in a sealed container, thus the pressure increases as water vapor increases and tries to expand in a sealed container. But your fruiting chambers are not sealed. Moist air is less dense then dry air. So in comparison, your upper tub will be more dense then your lower tub. So air would fall through your upper tub, down to your lower tub where the air has most moisture. So if your lower tub had no air holes, and was able to force the air up through your upper tub, then it may succeed. I don't know about building terrariums, but I do know about chemistry and science. I fell in love with Mycology, so I am learning on my own, cheaper then going to school at the moment.

Edited by pepprodigy (02/02/09 11:53 PM)

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OfflineNibin
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9726847 - 02/03/09 02:08 AM (15 years, 1 month ago)

By increasing the temperature of the air inside the FC you will probably be dropping, not increasing the RH.

The higher the temps the more water you need to put into the air for it to be at 100%. And with passive evaporation of a flat water surface alone (no perlite, geolite etc to increase surface exposed to the air) I doubt you would be able to get enough vapour into the air to keep up.


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OfflineChronicMuffin
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Nibin]
    #9726869 - 02/03/09 02:20 AM (15 years, 1 month ago)

As i say to everyone, Roger has spoken... hop to it! (o gee ;p! ignore my witty banter)


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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: pepprodigy]
    #9727480 - 02/03/09 08:55 AM (15 years, 1 month ago)

Quote:

pepprodigy said:
Moist air is less dense then dry air.




:shocked: Truly I'm shocked... All these years I thought it was the other way round, but you're right..! I guess that could be a reason for the design to fail.

If I get my hands on a spare heater and tub I'll give it a try anyway and keep you guys posted..! :smile:

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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Nibin]
    #9727501 - 02/03/09 09:01 AM (15 years, 1 month ago)

Quote:

Nibin said:
And with passive evaporation of a flat water surface alone (no perlite, geolite etc to increase surface exposed to the air) I doubt you would be able to get enough vapour into the air to keep up.




There would be a layer of wet perlite at the bottom of the inner tub :smile:

It would be like a standard-fare shotgun terrarium, with the addition of a pool of hot water and air underneath to keep things warm (my main objective right now- I haven't had the chance to do measurements on humidity yet).

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OfflineRogerRabbitM
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9727605 - 02/03/09 09:24 AM (15 years, 1 month ago)

Quote:

As far as I know, pressure increases with heat (exactly because, like you said, the molecules push away from each other more)



Only in a sealed environment such as a closed pressure cooker.  In open space, pressure decreases with heat.  The molecules are farther apart, thus less density.

Quote:

and thus air tends to flow from the hotter areas towards the colder



Incorrect.  Air flows from high pressure to low, regardless of temperature.

Quote:

and this is why warm air always flows upwards, where the pressure is lower.



Hot air flows upward because it is less dense than cold air.  This is not related to pressure, but rather to density.  It's the principle that hot air balloons operate on.  It's also the same principle that causes down slope flow from mountains during high pressure weather systems, resulting in colder air in the valley than at the summit, the opposite of the usual scenario, where temperature decreases as elevation increases.

Quote:

pepprodigy said:
Moist air is less dense then dry air. 




This is absolutely correct.  It's the reason aircraft need a longer runway for takeoff on wet days than on cool dry days.  It's also the reason the engine in your car or motorcycle develops less horsepower on rainy days than on dry days, temperature and pressure being equal.

The bottom line is to experiment all you want and report the results, but understand that the shotgun terrarium is engineered on sound science.
RR


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"I've never had a failed experiment.  I've only discovered 10,000 methods which do not work."
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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: RogerRabbit]
    #9728586 - 02/03/09 01:28 PM (15 years, 1 month ago)

Quote:

RogerRabbit said:
The bottom line is to experiment all you want and report the results, but understand that the shotgun terrarium is engineered on sound science.
RR




Wow, take it easy, friend...! I didn't claim otherwise. But I'm a scientist myself (although thermodynamics are never involved in my field), and so I've learned to question everything - even authority figures such as yourself! I'll agree that the shotgun terrarium is a brilliant piece of engineering, but for the sake of other people reading this thread, I'd like to clarify something:

For a constant volume, pressure _increases_ with temperature. Now, for a non-controlled volume, pressure may not increase as you correctly say, but - humidity and density parameters aside - it definitely does not decrease as a result of the temperature rise alone. Density, yes, but not pressure. This as stated by the ideal gas law (I think it's called that).

Cheers!

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OfflineNibin
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9729224 - 02/03/09 03:38 PM (15 years, 1 month ago)

Quote:

shroomey said:
Quote:

RogerRabbit said:
The bottom line is to experiment all you want and report the results, but understand that the shotgun terrarium is engineered on sound science.
RR




Wow, take it easy, friend...! I didn't claim otherwise. But I'm a scientist myself (although thermodynamics are never involved in my field), and so I've learned to question everything - even authority figures such as yourself! I'll agree that the shotgun terrarium is a brilliant piece of engineering, but for the sake of other people reading this thread, I'd like to clarify something:

For a constant volume, pressure _increases_ with temperature. Now, for a non-controlled volume, pressure may not increase as you correctly say, but - humidity and density parameters aside - it definitely does not decrease as a result of the temperature rise alone. Density, yes, but not pressure. This as stated by the ideal gas law (I think it's called that).

Cheers!




P*V = nRT

If you increase temperature the product of P*V has to increase. When heated a gas increases in volume and its density decreases. The air rises causing a partial "vacuum" and as a result, a lower pressure.

It isn't as simple as the ideal gas formula. Real life sadly, is hardly ever ideal. But anyone who has looked at a weather map hard for a while knows that low pressure = hot air and high pressure = cold air.


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Invisiblethehappymushroom
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9729318 - 02/03/09 03:57 PM (15 years, 1 month ago)

I swear we get like 50 of these a day lol.... We should put a Locked thread up with all things humidity.Or RR's notes on fc's/humid There really descriptive and to the point.
  There's not really any Humidity Info on this site that ive seen. Only humidity teks and such. it would really save alot of Spaces from us noobs just getting started.. then spendin time to think about somthin for a day or 2 and then finding Out it would never work lol.. Just a thought.

cool concept for keeping your lizards warm tho dude:stoned:.Good luck brosive, keep it shroomey.


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Offlineshroomey
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Nibin]
    #9729362 - 02/03/09 04:03 PM (15 years, 1 month ago)

Hi Nibin,

Thanks for clarifying things - what you say makes perfect sense.

I'm going to take the risk and sound over-persistent, but I assure you I'm not - I doubt I'll go into the trouble to build the design I proposed (given that a simple lamp will suffice to solve my heating problem). But this is becoming something of a mind experiment to me, and having nothing better to do at this time, here's a thought:

RR suggested that, the lower pressure underneath (in the lower chamber) would cause the air to flow downwards, thus drying the upper chamber. But as Nibin said (and from the little I know, on which this design was based), the hot air would tend to flow upwards (itself causing the lower pressure below), thus going through the wet perlite at the bottom of the upper chamber and providing extra humidity in there... Any thoughts about what would actually happen if I built this thing? Perhaps a cycle?

I know a simple experiment would answer this, but I lack the resources right now...

...Then again, maybe I should just move this thread in a science forum :P

Thanks to everyone for helping

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OfflineNibin
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: shroomey]
    #9729385 - 02/03/09 04:07 PM (15 years, 1 month ago)

Hot air would rise, causing the humid air inside the FC to flow down, get heated and its RH diminished. Then the warm air would rise, cool off to past the dew point and create loads of condensation everywhere.

This is just a personal theory on what would happen. The best way to confirm it would be to build one and test it.


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OfflineScientificClown
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Re: Shotgun terrarium modification: Introducing extra warmth & humidity [Re: Nibin]
    #9854043 - 02/24/09 01:22 AM (15 years, 26 days ago)

I hate to be a nerd... but hey, its what i do. So here goes.

Pressure increases with heat. as the air in a terrarium is not confined, it expands, becoming less dense. THIS IS SCIENCE, IT HAPPENS!

HOWEVER:a parcel of warm air (or any gas that is warmer than the surrounding gas) will rise as it becomes less dense. It's place will then be taken by descending cool air. This is called convection, and it results in the mixing of air, particularly in a confined environment like a terrarium. Just imagine a boiling pot of rice. As it boils, rice floats to the top, cools and then sinks again. The same would occur in an internally heated terrarium.



Something else that has not been considered is that relative humidity in a fixed parcel of air DECREASES with an increase in temperature, because as air heats, it is able to carry more water. SO, warmer air will dry out the mushrooms, unless extra moisture is provided to saturate the air.

In order to humidify air to saturation point, all you need to do is take moderately humid warm air and cool it. As it cools, it will rise in humidity, until it reaches dew point, at which condensation forms. This is why cold windows fog when you breath on them. I'm sure that with a little thought, you could incorporate this element into your design.

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