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De-Mist-ifying A Cool Mist Flow


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#1 bluehelix

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Posted 20 February 2006 - 09:23 PM

For those of you who use the cool mist in a small tub chamber, you've probably experienced some mist output. Mist, for those of you who don't know, is not the same thing as humidity (water vapor). Mist is water in a liquid state in tiny balls in the air. If the balls are super tiny, you get a white cloud-like effect as you've seen from ultrasonic humidifiers. If the droplet size is larger, you get what you see coming out of a cool mist.

Normally, when one uses a cool mist in a home, the balls evaporate in the air or immediately after landing on the surrounding surfaces. That is because in a normal home the relative humidity is low (probably under 40% if someone is using a cool mister). In a mushroom tub, though, the relative humidity can be in excess of 90%, and those drops can linger and collect on the surfaces they land. This can be a problem leaving standing water on the mushroom chamber floor or, worse yet, on mycelium.

When cool mists were first recommended for tiny mushroom chambers, it was suggested that the output of the cool mist be run through a long garden hose to make sure the mist hits the hose's walls. This was a basic way of demisting the output, but it doesn't work perfectly (some mist makes it out) and it won't work for larger hoses very well at all.

A better way is to use a small amount of some material that will stop the mist but allow the humid air past with almost no back pressure (since cool mist units can't push air). This is a pretty hard material to find, but I found something that works very well, excelsior moss (many craft stores carry it):

http://mycotopia.net...=1&d=1140488525

This stuff is amazingly resistant to mist yet allows humid air through with very little back pressure. I have been using it in my 1" PVC tube in my own set up for some time now:

http://mycotopia.net...=1&d=1140488478

I use about the amount of a golf ball in the tube. I don't pack it tight, just tight enough to get the job done. By using this material, the output is not restricted too much and is mist-free. Because liquid water isn't thrown out, the water chamber last a long time. I don't have to fill the chamber but once every four days to a week even running 24/7.

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#2 chill

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Posted 20 February 2006 - 09:35 PM

Cool thought.

I had a copy of one of PFs early DIY and he suggested pop bottles as de-misting resevoirs. Of course they fill up and have to be emptied etc.

Pain in the butt IMO.

Any problems with growing contams on the moss?

#3 bluehelix

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Posted 20 February 2006 - 09:46 PM

There might be problems normally, but because the chamber water sits for so long (up to a week), I always throw in a couple tablespoons of hydrogen peroxide with each fill of the cool mist. That pretty much kills off anything before it could get started, even bacteria.

#4 bluehelix

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Posted 22 February 2006 - 03:05 AM

One thing I should add to this post is that this form of de-misting works REALLY well if done right. That means that the output is really mist free and close to 100% RH. Without any mist in the air, it will demonstrate temperature/humidity laws of physics which may not be expected. For example the let's say the cool mist output is at 100% RH at 73F (cool mists do cool the air slightly). Now let's say that air heats up to 78F in your chamber. The RH of that air will drop to around 85%. If you want the air to be more humid in the chamber you'll have to introduce some form of standing water in the chamber like wet perlite, wet casings, misted walls, etc. Personally, I'd rather control where the water will be myself rather than spray mist all over the place.

#5 Lazlo

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Posted 22 February 2006 - 05:07 PM

So it seams that the colder water molecules from the cool mist collect together in the air and drop the RH? This filter collects them early and prevents heavy droplets from forming in the air and settling down in your chamber and substrates? Makes perfect sense...

#6 Hippie3

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Posted 01 March 2006 - 10:36 PM

nice post.
i do similar
except i use a small amount of loose polyfil
i figure a synthetic fiber is less risky

#7 xxanxx

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Posted 01 March 2006 - 11:40 PM

^^I'd say that's correct. I also use polyfill and I have never had a problem.

#8 Lazlo

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Posted 01 March 2006 - 11:47 PM

I put a submersible aquarium heater in mine to avoid this. The warm water provides a nice warm fog when on, rather than a cold sloppy mist. The RH % went up around 15% per double tub after the addition. I'll try this as well..

#9 bluehelix

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Posted 02 March 2006 - 01:31 AM

Lazlo, that's a great idea. Maybe I'll try it if the temperature delta makes it difficult to get the RH high enough.

Also, I have tried polyfill very loose and the cool mist cannot blow through it well. Even at the most loose I could go, it cut flow a lot when it got wet for me. This stuff, on the other hand, gives almost no resistance to air flow.

#10 Hippie3

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Posted 02 March 2006 - 08:19 AM

agreed, i do have that problem with polyfil once its' matted/saturated,
a bit of a PITA.
yours is larger diameter but more airspace too.
got me thinking...
thx
:bow:

#11 Lazlo

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Posted 02 March 2006 - 06:00 PM

It works nice Bluehelix. The only downfall I can see in your case is the lack of air exchange for Pans. In order for the water to be warm in the tank consistantly, there needs to be a period when the humidifier is off. The damn impellar cools the water down in about 15 minutes when on. Thus; it runs for 15 minutes every 2 hours to maintain a warm tank. It speeds up funk as well. So the humidifier needs to be cleaned every fill up. Not a big problem really..

Then again, I haven't added any bleach or peroxide to the fill water either. Just tweaking for now..

#12 Hippie3

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Posted 02 March 2006 - 06:37 PM

i can't recommend putting bleach in a cool mist
leaves ungodly amounts of salt residues

#13 sudont

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Posted 03 March 2006 - 02:22 AM

Very interesting thread! I'm using a Cool Mist with a foot long, three-quarter inch (outside diameter) hose in a 63 liter chamber. Plus, I have Perlite on the bottom. Yet, according to my re-purposed cigar humidor hygrometer (I know, I know...poverty), I'm only getting around 85% RH, and I can't figure out why.
At first, I thought maybe the air flow was so high that it was actually pushing moisture out, you know, air drying the whole works. But opening up a vent in the Cool Mist didn't help, and in fact dropped RH a coupla percentage points.
Given what has been posted above, do ya'll think I should somehow try to impede the flow of mist as above? Would that actually increase the RH? Or perhaps something else would help? Appreciate any and all input!

#14 bluehelix

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Posted 03 March 2006 - 02:31 AM

sudont, what's probably happening is that the output of the cool mist is 100% at a lower temperature than the chamber. Remember you heat up air a tiny bit, and the RH drops like a rock. It's like 5F drops it about 15% or something. Take temperatures at your cool mist input and your chamber. If there is a big difference (like more than a couple degrees), that's what's going on.

#15 malefacter

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Posted 05 March 2006 - 11:48 AM

that moss stuff looks a lot like the filter material used in swamp coolers its like wood strips ( hmm maybe i could grow something on it? ) if it is the same its easy to find at hardware stores and is cheap

#16 golly

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Posted 05 March 2006 - 03:53 PM

There is also stainless steel wool u can buy in the paint section of a hardware store or maybe plastic wool they put in some Easter baskets -now there's a good reason to by chocolate ...heh...
This is a great idea you have BH ...I have noticed blue spots forming on mushroom caps from the mist that contains h2o2 or bleach ..Wonder if u could rig the filter fibers so that excess water condensing on it ,just rolls back into the resevoir....

#17 hogwild

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Posted 05 March 2006 - 04:10 PM

Because liquid water isn't thrown out, the water chamber last a long time. I don't have to fill the chamber but once every four days to a week even running 24/7.


the water does go back into the chamber i believe

#18 golly

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Posted 05 March 2006 - 05:55 PM

oh yeah ....i see it now.....kewl stuff...




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