For the serious hop head who demands an aroma that equals a hop field at harvest, we have a device called the hopback. A hopback can be thought of as a percolator for hops that is able to produce liquid that is laden with hop essence. The devil is in the details.
Boiling extracts essential hop oils. The heat of the wort and mechanical action in the boil dissolve, extract and isomerize (changes the chemical composition) of hop alpha-acids.
Some hops are typically added soon after the boil begins. These are bittering hops to provide the foundation for beer’s balance between malty-sweetness and bitterness. An hour’s boil evaporates most of the hop aroma. A later flavor addition restores hop taste and a very late addition provides aroma. Of course, not every recipe calls for hop aroma. But the identity of most APA or American-style IPAs is marked by boatloads of hop aroma.
While a good aroma can be achieved by adding hops late in the boil or at its conclusion, a different aroma can be achieved by passing hot wort through a bed of hops on its way to the chiller; the aroma is immediately dissolved into wort.
Our hopback is quite simple and should perform best with post-hopback wort cooling. The design objective is to enable hot wort to extract maximum flavors. The hop bed, acting as a filter, needs to be loose enough to absorb some trub from the kettle without clogging, yet compact enough to force the wort to flow through the hops: wort in — wort plus hop aroma out.
Preventing debris from flowing into your fermenter is important. Some particulates are inevitable, but to keep out the majority of debris, we need a screen to prevent large particles from exiting the hopback, as the hop bed collects most of the particulate matter. Brass window screen is abundant and found in most hardware and home stores. Stainless steel screen is desirable, but harder to find and more expensive. The screen (filter) needs to fit tightly to the diameter of the tubular hopback and be supported so it will not distort or tilt under pressure. Pressure fitting should be sufficient.
In this segment of Projects we will create two easy to use hopbacks for different applications. One is constructed from copper pipe with brazed connections, the other built from CPVC (schedule 40) plastic, which is meant for potable water service. Though Schedule 40 pipe is meant for service at or below 140 °F, at zero pressure and short contact duration there is little danger of failure.
To size the project, we decided on 2″ (50 mm) pipe, easy to find at home stores. The connectors were easy to find and purchase. Pipe sections had to be purchased in 10-foot lengths. Ten feet of CPVC pipe is only $3, but 2″ copper pipe is $6 per linear foot! Luckily, I found a plumbing shop that agreed to sell a scrap. Maybe you’ll have the same luck and save yourself some money.
The next question was, “how much hops should a hopback hold?” There is no clear answer. We relied on the fact that most post-boil aroma hop additions are 0.5–1 oz. Therefore if the hopback tube would hold 2 oz. there would be enough hops to satisfy the hoppiest of hopheads. Of course, you can adjust the size to hold as much as you anticipate using.
Another technical problem is leakage. End caps and solder caps should be soldered or solvent welded to a tube. That’s why stainless steel or brass pipe and screw-on caps would be nice, albeit expensive. We’ll show you how to add O-rings or a permanent addition of food-grade sealant formed into a gasket to limit dripping and we’ll add a safety wire to hold everything together. One detail we’ll address, but not solve, is how you will attach the finished hopback to your brewing system. Ready to start? Grab a hacksaw or pipe cutter and head for the workshop.
Step by step
We weighed out 2 ounces of hops and stuffed them into a pipe, tamping to what we think is a decent
compaction. The tube length required for this amount of hops is 12 inches. That became our basis dimension, 2″ inside diameter (i.d.) x 12″.
Cut CPVC (schedule 40) or copper tube to length. Set the tube aside after smoothing any sharp or uneven edges — a medium sandpaper will suffice.
Drill a pilot hole into end caps. Whether copper or CPVC, you must attach an inlet and outlet. I decided that the copper version would use male/female 1/2″ pipe thread couplings silver brazed to the end caps; silver solder might work as well. Use threaded fasteners screwed into the plastic for the CPVC end caps.
Copper — Drill a 1/8″ pilot hole into the center of your end cap, followed by successively larger drills. Drill holes that equal, or are slightly smaller than, the internal diameter of the fitting to leave a shoulder to weld or solder to. The best way to do this is to purchase an inexpensive step drill. Or, you can enlarge holes with a large diameter rat-tail file.
CPVC — Same process as the copper version, but enlarge the hole to just under the fitting’s thread diameter. 2″ CPVC end caps are almost 1/4″ thick and the brass barbed fittings sufficiently sturdy to self-tap the threads. Note that for the female outlet-side I used a flare fitting and flare cap on the inside to secure that fitting. Flare fittings have a high shoulder and will require an O-ring, or forming a shoulder (leak prevention) with aquarium-grade silicone seal. We suggest the silicone seal.
Once your end caps are constructed, run a bead of silicone seal. For copper end caps, the better placement for sealing will be inside the copper caps. Run a small bead of silicone seal (I used black) at the bottom of the cap. Wet your finger with alcohol (an important step) and smooth the silicone to create a smooth sealing surface. Allow to dry.
For CPVC, with its greater wall thickness, run a thin bead onto the tubing end and smooth. This may be an unnecessary step as the CPVC fits so tightly, tube to cap. I worried about how to hold the hops, first envisioning brass-mesh cylinders and other complex solutions. Then it hit me; we all have tightly woven mesh hops enclosures in our brew kit! Those ubiquitous cotton-mesh hops bags are perfect for this use. Stuff the required hops into a bag; stuff the bag into the tube.
To prevent stress and strain, make some strainers out of brass door screen. Place your tube end, copper or CPVC, onto the brass screen and trace a circle with a Sharpie marking pen. Then trace inside the lines with silicone seal, being certain that the seal penetrates the copper mesh. This will both provide a sealing surface and prevent sharp ends from cutting you or the hop bag. Cut out the circle, just large enough to fit into the end cap.
Clamping. It is imperative that you hold all three pieces together tightly. Whether you use a bungee cord, safety wire or a pipe clamp, you must secure the end caps to the tube. The wort will be near boiling. Should something come apart the potential for injury is high and the loss of your beer is certain. The simplest safe restraint I can think of, that works on either hopback, is a pair of custom made hooks connected by a safety wire.
Using 8–10 inches of brass welding rod, bend a circular form around a 1″ pipe. Bend the remaining rod at 90 degrees, then create another circle. Make a second unit. Once the hopback is ready, loop one hook around each end and secure with a light gauge safety wire.
Constructing an attachment. Your brew rig and mine differ. My system uses quick-disconnects and the hopback will be connected with stainless steel pipe. Yours might use reinforced tubing and clamped barbed fittings, as shown on the PVC hopback. Please use reinforced or high-heat tube for all connections, the wort is still scalding hot.
Your completed hopback is just the beginning. You still need to answer many questions for your personal brewing: How much hops? Pump through, pull through or gravity feed? Type of hops? All of these questions depend on the necessities of your brewhouse and brewing process. Enjoy!