re: Yeast CO2 questions

>I've just rigged up the CO2 yeast method following recipe posted by 
>David Webb. I've connected it to an air-stone while building a reactor. 
>Immediately noticeable effect are bubble streams coming out of cutted 
>sections of stem plants and reduction in my pH. That must be a good 
>sign. Now my questions:
>1) Do I leave the CO2 bubbles coming out at full blast or reduce it with 
>the air valve? 

I've never tried this, so I don't know for certain what effect you'll have.  I 
suspect that the increased pressure will acidify the water more and affect the 
CO2 production rate of the yeast.  However, if you do increase the pressure, it 
may become very difficult to adjust the pressure down again without the swill 
fizzing into the tank.  I accidentally left a valve shut off once, and when I 
remembered to open it, the generator fizzed out into my tank.  I was rewarded 
for my carelessness with a scum on the water's surface that took weeks to get 
rid of, despite my surface skimming trickle filter.  (My a.crispus were 
blooming and the stalks messed up surface flow.)  I'm glad that I did remember, 
or else I'd have had to write up another yeast CO2 accident story.  (Once is 
forgivable, twice would make me feel very stupid.)

>2) Will reducing bubbles increase the preassure in the bottle and 
>explode like that was posted in the last few mail.

Enough pressure will cause any bottle to explode.  If you have silicone tubing 
attached to the bottle, you will probably rupture the tubing first and wind up 
with an "out of control fire hose" effect.  This is what I seem to remember 
happened in the last catastrophe posting.  I actually had a sealed glass bottle 
explode on me, throwing glass all over my apartment.  I'm still picking up 
glass occasionally, three months later.

If you have some kind of release (i.e. the valve is slightly open) you probably 
won't have this problem.  I'm not sure that the CO2 production rate is great 
enough for you to easily adjust pressure inside the system though.  You might 
be able to if you use a needle valve instead of a ball valve.  Really, I'm just 
not sure about this.

>3) Is it true that if I reduce the amount of yeast in my next mixture, 
>would it last longer but with less bubble rate? Is there a catch to 

Yes, it is true.  I don't know if there is a catch to this.  Since I upped my 
sugar from 1.5 cups to 2 cups, I get about 3 weeks of use out of a bottle 
before it slows to a small bubble every 20 seconds or so.  Since I use two 
bottles, I can have one relatively fresh at all times.  I currently use 1 tsp. 
of yeast and 1 tsp. of baking soda to buffer against pH crash inside the 
bottle.  If you use baking soda, you might want to use less of it as well if 
you use less yeast (this is really hyposthsizing on my part).

I've tried various ways of "purifying" the initial CO2 when a generator is 
first hooked up.  The primary way that I tried is to squeeze the bottle so most 
of the air is gone when I screw it onto the cap (the cap is permanently 
connected to the CO2 reactor system).  I found that this is a good way to suck 
lots of tank water into your CO2 generator.  Since this isn't my goal, I've 
decided to just let it purify itself and put up with a little air in the system 
for a short time.

Hope this helps,

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc.
(214) 575-3443 (voice)		MSGID:		DAWB
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