I should really have a whole series of posts under the banner ‘things you don’t know about where you beer comes from’.
Yesterday we had an absolutely shocking day in the brewery. We lost about 500L of beer and I’m not really sure how. Fortunately we lost it before we had to pay duty on it so it’s not as bad as it might have been.
As I mentioned in an earlier post, we’ve had some problems getting the hang of the filter. Today was another one of those days when the beer would not filter properly. I believe I know the cause of the problem now.
One of the things I’m doing in the brewery is topping up the fermentation tanks (FVs) with fresh water after the main fermentation has finished. Because fermentation is so vigorous, producing a lot of foam as well as carbon dioxide, FVs have a nominal capacity of about 75-80% their actual physical volume. Since we have such a small brewery, topping the FVs up after fermentation has subsided is a good way of producing more beer form the same amount of kit. This is so-called ‘high gravity brewing’ and all the big commercial breweries do it. It can have detrimental affects on the beer if it is taken to extreme ends, like brewing at twice the normal strength, but at the level we’re doing it at, there are no detrimental effects. It is also such a simple thing to do, it’s quite possible brewers in olden days did something similar for the same ends.
Yesterday I topped up an FV with cold water and to make sure it was adequately mixed, I recirculated the beer for a short time. What I hadn’t adequately thought through, however, was the fact that this would obviously resuspend all the yeast and hop debris that had settled in the tank at the end of fermentation. I should have just left it there, but as we needed to bottle that beer to even up our inventory levels, I filtered straight out of the FV into the Bright Beer Tank (BBT). Only the filter clogged up almost immediately. This meant that only tiny amounts of beer were getting through unless I cranked up the pressure enormously, in which case loads of beer went spurting out the sides. We lost a fair amount to spray thinking about how best to solve the problem before stripping the filter down and adding more filter sheets. This clogged almost immediately again. I’m always reluctant to strip the filter press down when it’s ready to filter because the assembly has to be flushed with hot water to pasteurise it and to drive out any air bubbles out. Air in the filter sheets leads to high levels of dissolved oxygen in the beer which causes oxidation and staling. And we only have limited quantities of hot water. Eventually we stripped it down again and this time only put coarse filter sheets in as opposed to a mixture of coarse and fine filters like we normally do. This filtered well for a while before clogging again. The sheets can be reused, if we flush them with copious amounts of water, which I did.
Somehow the long and the short of it is that we ended up with much less beer than when we started.
I’m worried that the owners are about to lose patience with me.