Recent content by Greg.L

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  1. G

    60L fermentor

    You obviously haven't read my other posts, the partial pressure of oxygen is lower in the fermenter so it is a negative pressure.
  2. G

    60L fermentor

    Infection microbes are ubiquitous in the air. You have to open your fermenter to pitch yeast, that's enough to let infection in. I didn't say all infections were aerobic, just all the ones you see on the surface. (Lacto doesn't sit on the surface). Because they are on the surface they don't need...
  3. G

    60L fermentor

    If you see an infection floating on the surface of your beer, then it is definitely an aerobic infection caused by too much oxygen in the headspace. If it isn't obvious on top but causes a vinegar smell, that is also aerobic. Other infections are harder to diagnose.
  4. G

    60L fermentor

    In my opinion most infections are caused by oxygen in the headspace. It's a misconception that infections are caused by poor sanitation, infections are usually aerobic organisms and need oxygen. Of course, sanitation is one of those variables, like oxygen exposure, that homebrewers have control...
  5. G

    60L fermentor

    My main concern with headspace and gladwrap is the potential for infections, but it can't be good in terms of oxidation either. The basic principle is to always try to minimise the oxygen getting in the fermenter, oxygen contact is one of the variables homebrewers have control over, along with...
  6. G

    60L fermentor

    Your calculations seem good but the permeability figures were for hdpe. The figures for gladwrap are a lot higher so probably multiply your figure for gladwrap by ten. I wouldn't be surprised if as you say the figures from that site are on the high side. HDPE fermenters work fine when full...
  7. G

    60L fermentor

    There's no controversy really, it's just a choice between the "she'll be right" brigade and the " better safe than sorry" camp. The only controversy is when the "she'll be right" brigade try to make out their method is perfectly safe.
  8. G

    60L fermentor

    There is this thing called google, if you search oxygen permeability of hdpe plastic you might get some results. Most fermenters are hdpe. One site gives a figure for hdpe of 4000 cm3-mil/m2/day but I am not sure what the thickness is. The thicker the wall of the fermenter the less permeable it...
  9. G

    60L fermentor

    Mainly through the seal and the walls of the plastic fermenter. The volume of headspace is significant partly because at the surface of the beer is where most infections take hold. The yeast cells in the beer act to mop up a fair bit of oxygen. Hop chemicals also have antibiotic powers. The...
  10. G

    60L fermentor

    This is the point - that oxygen is not just being consumed by the beer, but by various aerobic microbes (germs). If you think it is irrelevant that more oxygen is being drawn in then I obviously can't convince you. You are obviously more convinced by all the people on this forum who reassure...
  11. G

    60L fermentor

    The point is that the pressure of oxygen inside is much lower than the pressure of oxygen outside the fermenter. "Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow"
  12. G

    60L fermentor

    for a given pressure of oxygen, if you increase the volume you will increase the mass of oxygen. That oxygen is available to react with the beer and any micro-organisms on the surface of the beer. As the oxygen reacts and dissolves the partial pressure at the surface drops so oxygen moves...
  13. G

    60L fermentor

    Some good quotes from sources. "Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow. Gases dissolve, diffuse, and react according to their partial pressures, and not necessarily according to their...
  14. G

    60L fermentor

    My point is that if a container is full of co2 and not totally sealed, (the situation of a fermenter after the initial fermentation has died down,) the fact that the whole volume is full of co2 doesn't stop oxygen entering. Co2 doesn't have to leave for oxygen to enter, oxygen can get in even as...
  15. G

    60L fermentor

    I guess if it worked once it must be OK.
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