Wednesday, August 28, 2013

Fun with a Spunding Valve

Few if any homebrewers are familar with a spunding valve.  It's actually used commonly in commercial breweries, but only a small subset of homebrewers could consider using it as it requires a fermenter that can withstand 10 PSI or so of internal pressure (such as a Cornelius keg).  Since most of us use carboys or plastic buckets to ferment, a spunding valve is not an option.

A spunding valve is basically a pressure relief valve that is used on commercial bright tanks to carbonate the beer using the CO2 generated during the final stages of fermentation.

An adjustable pressure relief valve is the key to dialing in just the right amount of pressure, while allowing excess pressure to bleed off harmlessly.  This pressurized CO2 yields the same result as connecting a CO2 bottle to your keg....your beer gets carbonated!

Last year, I began fermenting in Cornelius kegs.  I can't recall why, but it was then that I found a thread on one of the homebrew forums describing how to build a spunding valve.  It allows you to get your beer carbonated as fermentation finishes using the CO2 produced by the yeast as it eats away at the last vestiges of sugar in the wort.  Some claim that you can go from pitching yeast, to drinking beer in 10 days on some low gravity beers by using this method.

After a few weeks of thought, and mulling over how to make a functional yet affordable version of a spunding valve I could live with, I ordered what I needed and assembled what you see below.

A standard gray gas fitting with barb is shown at the bottom connected to the keg.  I used hose clamps and a short piece of tubing to connect to a transition fitting that mates with the adjustable pressure valve (black body with round gray knob).  To the left of the valve is a pressure gauge that monitors pressure in the keg.

Cornelius kegs are rated to 140PSI, and they also have a built-in relief valve on the lid (at least mine do), so maintaining 10 PSI does not pose any danger.

The biggest challenge in using these is figuring out when to put them on the keg.  When I pitch the yeast, I remove the Gas In fitting and tube, and force a piece of tubing over the threaded nipple that sticks out of the keg.  The tubing (blowoff tube) feeds into a small jar of water.  If you fill the keg too much with wort, the krausen will push up into the tube and into the jar.  You need to wait until this settles down before putting the spunding valve on, or you'll end up with all of that in your pressure relief valve and gauge..yuck.

BYO has an article written in 2007 by Marc Martin describing the spunding valve and when to attach it.  He says that you should wait until you're within 0.005 of final gravity, but I usually don't wait that long. I just wait for the krausening to calm down, and then set the pressure to 10PSI and stick it on there.

Chris White's book about yeast discusses the effect of pressure on yeast, and he says that you should keep it under 15PSI.  If you set it to 10PSI, you should get good carbonation, and not hurt the yeast too much.  It's worked fine for me.

Once fermentation stops, I rack from one Corny keg to another using a short tube with liquid fittings on each end.  This transfers the beer without exposing it to oxygen (assuming you've purged the target keg with co2 prior too the transfer).  Just make sure you divert the initial burst to another vessel so you don't get all the yeast from the bottom of the fermenter keg into the target keg.

You'll need your CO2 tank handy to help force all of the beer over into the target keg. I usually set my regulator to 5 PSI or so...just enough to push it through the tubing.

Let me know if you have any questions or comments.  I'm writing this with a glass of Merlot sitting next to me, so I may have missed some details!

The bag is the key to BIAB!

Once I realized the benefits of Single Vessel brewing (AKA Brewing in a Bag), I eagerly read as much as I could find regarding this method.  I rushed out to Walmart and purchased a $5 Voile curtain and sewed myself a bag.

Several brews later, and I was hooked.  The technique was beautiful and made great beer!  But then one day, I decided to split my grains among 2 bags....but this time I used the infamous Home Depot 5 Gallon paint strainer bags that are often used for hops additions.  I simply used binder clips to hold each bag around the edge of my brewpot.

Wow!  What a difference.  By splitting the grains into 2 bags, each bag was easier to handle, and actually provided more surface area for the water/wort to contact the grains. 

Additionally, when mashing was finished, lifting each bag out to drain was much easier, and even better, the wort flowed out of the bag much more freely it seemed.  Could it be that the paint strainer bags have a slightly coarser weave than the voile curtain???  Well, my eyes are no longer able to see that level of detail even with glasses, and I sold my microscope/chemistry kit decades ago.  I took some pics with my phone camera, and while blurry, it does appear that the paint strainer bags are significantly coarser in weave than the voile.

So for now, I'm sticking with 2 paint strainer bags and retiring the voile. Actually, the voile bags came in handy this weekend when I harvested my hops.  I just dumped them into a voile bag and hung it next to a fan.  Twenty-four hours later, I had dried hops!

Please let me know if you've tried different types of material for your grain bag, and what your results have been.