[Homeroast] OT: Gases, was Re: Storage right after roasting

Mike Koenig koenig.mike at gmail.com
Tue Aug 26 20:37:09 CDT 2014


Sorry for the slow reply here - I fished this out of my spam folder...

If you fill a container with two gases of different densities, they will
mix, and fairly quickly.  The speed will depend a little bit on the
difference in density of the two.  Over a period of time, the mixture will
become a completely homogeneous mixture.

--mike




On Tue, Aug 19, 2014 at 11:03 PM, Andrew Thomas <adt0611 at yahoo.com> wrote:

> Mike, what happens in a closed container with 2 gases, say O2 and CO2,
> where one gas is heavier than the other? I assume they do not remain
> completely separate, correct? Do they eventually diffuse and become a
> uniform mixture? Or do they become a graded mixture, with the heavier gas
> more concentrated at the bottom and the lighter one more so near the top?
> And if the top of the container is open, will the heavier gas diffuse into
> the atmosphere?
>
>   l ALWAYS be mixed with O2.  You may reduce the concentration of O2 but
> it's my contention that in order to exclude meaningful amounts of O2 you
> need to either pull a vacuum on your container (pulling your volatiles out
> with it), or extensively purge with another gas.  On the timescale we drink
> our coffee it simply is not worth jumping through these hoops.  (Nitrogen
> flushed bags might be worthwhile for a commercial roasting operation who
> wants longer shelf-life).
>
>


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