I’ve actually been doing a lot of brewing over the past few months, creating and refining pilot recipes for 2MBC. Unfortunately, that doesn’t make for the most interesting brew days, let alone the most compelling blog material. Suffice it to say that NHC in San Diego lit a fire under my ass, and I hope to get back into some more experimental home brewing. Being able to go outside again doesn’t hurt either.
Anyway, one problem I’ve been trying to troubleshoot during this process has been the performance of my Belgian ale strains, specifically Wyeast 3522. It was turning out what I, at least, thought were some great beers in the past, but since moving to Leadville they’ve been chronically over-attenuated and phenolic, lacking in the ester profile that made me a fan of this strain in the first place. At this point, I’ve all but convinced myself that this is the result of switching from fermenting at about 12 psi to just under 10 psi, but lacking any way to control for that variable there is of course no way to be sure. Enter the spunding valve, a relatively simple device that allows one to ferment under controlled pressure.
I’m just kidding with the title, by the way; I see no major flaws in anyone else’s design. I just like callbacks. If you aren’t mechanically inclined enough to screw some fittings together, you can also stop reading here and buy one off the shelf, although it appears to have some issues, like maxing out at 15 psig and requiring a wrench to adjust the valve.
I do think that using an adapter as opposed to a length of tubing lends it a certain aesthetic appeal, but the chief advantage of this design is that all the parts are available on Amazon, which is convenient if, like me, you don’t have a big-box hardware store nearby — or if, like me, you just don’t like to leave the house. You can actually put one together for a few pennies less; I selected these particular components because they total $35.07 and therefore qualify for free shipping:
- Control Devices CR Series Brass Pressure Relief Valve, 0-100 psi Adjustable Pressure Range, 1/4″ Male NPT
- Zenport LPG30 Zen-Tek Glycerin Liquid Filled Pressure Gauge, 30 PSI
- Eaton Aeroquip 2090-4-4S Steel Pipe Fitting, Tee, 1/4″ NPT Female
- Eaton Weatherhead 9100X4X4 Carbon Steel SAE 37 Degree (JIC) Flare-Twin Fitting, Swivel, Adapter, 1/4″ NPT Male x 1/4″ JIC Female
You’ll also need a ball- or pin-lock quick disconnect (grey for gas), a nylon flare washer, and some thread-sealing tape (yellow for gas), but if you’re reading this I assume you already own a keg and therefore have that stuff on hand.
Piecing the spunding valve together was the work of just a couple minutes, obviously, and I’ve spent the subsequent week
playing with testing it prior to my first actual pressurized fermentation. Here’s the procedure I’ve come up with for setting the pressure:
- Attach the spunding valve to the liquid-out post of the (empty!) keg.
- Tighten the PRV to maximum pressure.
- Pressurize the keg via the gas-in post until the pressure gauge is reading somewhat higher than desired.
- Slowly back off the PRV until gas begins to flow.
- Once the gauge has dropped to the desired pressure, tighten the PRV until audible flow stops, then an additional one-quarter turn.
Using this procedure, after 48 hours the pressure had dropped from 10 psig to 6.5 psig — not ideal, but more than sufficient given the rate of CO2 evolution during fermentation.
Incidentally, don’t think you can cheap out and ignore the pressure gauge. These little PRVs are designed to be safety devices, after all, not precision instruments. You may be able to see in the photo below that the pressure is about 12 psig while the valve is set to a little over 30. You could elect to use a higher-range gauge, but with 30 psig being roughly what’s needed to carbonate at room temperature I don’t anticipate needing to go any higher than that.