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Humidification With K2Cr207

An intriguing, sterile humidification technique for people with access to some very basic lab materials.

Hey, I'm an environmental engineer but am working on a PhD in analytical chemistry. I've got some ideas from my masters research that may apply to shroom farming.

I worked with mixed cultures (activated sludge and anaerobic digesters) for removal of chloroorganics. Incidental to this research, I also worked with white rot fungus--which required 90-100% humidity and constant removal of CO2 .


The trick I came up with for humidification was to bubble my dry air through a glass diffuser into a beaker filled with a saturated potassium dichromate (K2Cr2O7) solution. The bubbles were slowed (to allow full humidification) by glass wool in the solution. I pulled this out of Lange's Handbook of Chemistry, the section on maintaining constant humidity. At 25 C, you get 98% humidity.

The reason this was preferable for my purposes is that I had to maintain a pristine, uncontaminated culture (sound familiar?) but I was introducing "dirty" air (aspergillum niger was my main problem). The dichromate solution is usually used for cleaning microbiology glassware because it is such an incredibly strong oxidant. And, as a non-volatile (inorganic salt) it stays in the jar.

Some caution must be taken when using this stuff. It'll soar right through your clothing, flesh, and bones; but, you can handle it with most lab gloves. It's also good for cleaning your glassware (terrarium or spawn jars) prior to autoclaving, as appropriate. The stuff turns from orange to yellow to green to blue as it is used up. Try not to flush it down your sink--heavy metal hazardous waste that will destroy a septic tank culture and do a great deal of damage to a publicly owned treatment works (POTW) and probably will get traced back to the source.

Also, I don't think a bubbling stone is a good idea--use glass (go to a college science supply store in the biology or chemistry departments and ask for a gas dispersion tube).

CO2 removal:

This one came from using a respirometer to measure bacterial growth rates, originally, but works well for CO2 in a fungal culture as well. A 50mL beaker (baby food jar...) is filled half full of sodium hydroxide or potassium hydroxide (NaOH or KOH) pellets. This is left in the growth chamber where CO2 is scavenged as long as you can see the pellets (it will eventually convert to an aqueous bicarbonate solution...it's still working while the pH is higher than the pKa for bicarbonate (around 6.3 ???) but it's cheap and available so replace it freely.

Don't get any metal into this stuff! Reaction is immediate and can be violent and results, often, in the liberation of H2 gas.

Another problem is that the stuff will regulate the humidity local to it (lowers to about 15% relative humidity). My strategy was to place the CO2 scrubber adjacent to the vent hole (necessary since air is constantly pumped in; the vent was attached to a hose the other end of which was submerged in dichromate solution to keep from contamination of the rest of the lab).

Using these 2 methods allowed me to maintain 95% humidity (+/- 3%) for 6 months, as measured continuously at the center of the chamber. As necessary (usually when replenishing the scrubber), I topped off the humidifier water.

If you try it, let me know how it goes--I'm completely out of the mycology/microbiology business now, but have been keeping up with developments, none-the-less. I might buy some perlite soon to test its compatibility with dichromate; I'll let you know what I find out.

Feel free to disperse this as you see fit. Any attribute (or grief) should be given to "Bun Justice Botanicals" and inquiry can be posted to alt.drugs.mushrooms or sent to me at bunjmarx@arches.uga.edu.

Disclaimer and warning: Any advice I give is worth the price you paid. Methods are only proven valid for white rot fungus, a delignifying agent valuable to the pulp and paper industry as an alternative to chlorine bleaching. I will maintain your privacy as well as I can, but this is a campus account and no more secure than any other campus account; I have nothing to hide, but if YOU do then take appropriate precautions prior to contacting me. Any and all requests for anything illegal will be deleted and forgotten (as will any abusive or otherwise stupid correspondence).

Good luck.


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