jarrodaden
Well-Known Member
I recently purchased a glass carboy thinking that I would begin using secondary fermentation. When I purchased the carboy, I put my wort into the carboy using it as the primary. It was later on this forum that I was told that the plastic bucket is better for a primary because when using the plastic bucket for a secondary, air could permeate into it causing undesired results.
I have been thinking about this and I am not sure that this is necessarily true. The fermentation process produces gas. Thus the reason for an airlock. The airlock will only release the gas when the pressure inside the fermenter is higher than outside.
That being said, if the pressure is higher inside than outside the fermenter I do not see how air would have any tendency to permeate into the fermenter. The only thing that might cause this is if the fermenter drops in temperature and the outside temperature becomes relatively higher there might be a brief moment that the pressure is actually higher outside than inside the fermenter. It is a fact that a set volume of gas will increase in pressure in the temperature rises and vice versa.
Some of us (including me) have seen this happened first hand when they put their wort into the bucket while it was still a bit warmer than room temperature. The following morning they come back to find the liquid in the airlock has been sucked into the fermenter. Set volume of gas is cooled and the pressure drops.
The key in my estimation is to transfer to the secondary while there is still a small amount of off gassing occurring so that the secondary will have a chance to build up gas again once it is sealed.
Another note - An "s bend" airlock has an added benefit if you understand the manometer principle. It will not only function as an airlock, it will give you an indication of how much higher the pressure is inside the fermenter vs outside. You don't necessarily need bubbles to know whether or not the fermenter is slightly under pressure due to off gas.
All of this said, I will still use the bucket for the primary because of ease of cleaning but thought it would be helpful to others to share a little science.
I have been thinking about this and I am not sure that this is necessarily true. The fermentation process produces gas. Thus the reason for an airlock. The airlock will only release the gas when the pressure inside the fermenter is higher than outside.
That being said, if the pressure is higher inside than outside the fermenter I do not see how air would have any tendency to permeate into the fermenter. The only thing that might cause this is if the fermenter drops in temperature and the outside temperature becomes relatively higher there might be a brief moment that the pressure is actually higher outside than inside the fermenter. It is a fact that a set volume of gas will increase in pressure in the temperature rises and vice versa.
Some of us (including me) have seen this happened first hand when they put their wort into the bucket while it was still a bit warmer than room temperature. The following morning they come back to find the liquid in the airlock has been sucked into the fermenter. Set volume of gas is cooled and the pressure drops.
The key in my estimation is to transfer to the secondary while there is still a small amount of off gassing occurring so that the secondary will have a chance to build up gas again once it is sealed.
Another note - An "s bend" airlock has an added benefit if you understand the manometer principle. It will not only function as an airlock, it will give you an indication of how much higher the pressure is inside the fermenter vs outside. You don't necessarily need bubbles to know whether or not the fermenter is slightly under pressure due to off gas.
All of this said, I will still use the bucket for the primary because of ease of cleaning but thought it would be helpful to others to share a little science.