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Re: exploding 2-liter pop bottles

On Tue, 1 Jun 1999, David Robinson wrote:

> Several digests ago (1054) while discussing DIY yeast reactors,
> Tom Barr wrote:
> > Be sure to use a ridged bottle !!!!!!!!!! Not a flimsy 2 liter
> > pop bottle. You'll be very sorry if ya don't! Noncollapsable
> > bottles are the way to go using yeast.
> I just wanted to clarify... what is the definition of a "rigid"
> bottle?

I think that Tom was referring to bottles with thicker sides than the pop
bottles, and a flutted pattern pressed in so that they resist collapse.
These are fruit juice bottles, sports drink bottles and so on.

> In the past, I've used standard 2-liter pop bottles
> without any troubles.  I consider these rigid because they hold
> their form when empty.  However, since they are made of plastic
> they are easily collapsable if you squeeze them.  Are these the
> ones that are not recommended?

I don't recommend them, because if a slight suction is applied at the
outlet, the bottle can collapse and the yeast mix gets pulled into the
tank.  The suction can be created easily if you're feeding the CO2 into
the intake of a power head, and the inlet gets slightly plugged.

> If so, has anyone had any experiences where these bottles
> exploded?

"Exploding" isn't the usual problem, but I imagine someone has done it.
Normally, the pressures in the bottle are very low.  If you use a valve to
restrict then CO2 flow, then pressures are higher.  If the outflow is
plugged pressures will increase until something gives and usually that'll
be the seal where the CO2 tube leads out of the bottle.  If that doesn't
give, then the bottle itself can split - "Explode".


> (BTW: I've even carbonated hard cider in plastic pop bottles
> without any problem... surely this is much higher pressure
> than a DIY yeast reactor!)

Certainly the pressure is usually low.  But if you put the yeast mix into
a sound bottle and seal it up, the yeast very well may build up enough
pressure to rupture the bottle.

Roger Miller