Three Mini Projects: Projects
Measuring specific gravity without a hydrometer
Not too long ago, I broke my hydrometer at probably the worst possible moment of the brew day: just after I had taken a test sample but before I had taken a specific gravity reading. In a panic, I weighed the sample and hydrometer test jar on a small digital scale and then marked the liquid level on the side of the test jar. Then I discarded the sample wort and filled the test jar with water to the line I marked previously. Then I weighed the water and the sample jar. By comparing the weight (actually mass, since my scale measures in grams) of the wort sample with the weight of the same volume of water, I was able to get a fairly accurate specific gravity reading.
The easiest way to prepare against a broken hydrometer is to have two of them on hand at all times (or to procure a refractometer). This isn’t always possible, so it pays to know the basic concepts of measuring specific gravity. For the purposes of measuring for homebrewing, specific gravity is the ratio of the mass of a volume of wort (or beer) to the mass of an equal volume of distilled water. For our purposes, it is fine to assume the known density of distilled water (1 g/mL) for the calculations that follow.
To measure specific gravity of your homebrew without a hydrometer or refractometer, you’ll need a scale calibrated to measure accurately (+/- 0.1 g) at small weights/masses. A common electronic jeweler’s scale will work fine. I ordered one from an online vendor a couple of years ago to measure small quantities of hops and spice additions. You’ll also need a graduated cylinder (50 mL or smaller), which should run about $5. For this project, I’ll work in metric units.
First, measure the mass of the empty graduated cylinder. If your scale has a tare feature, go ahead and zero out the mass of the cylinder at this point. If not, record the mass of the empty cylinder. Take a small sample of your beer using your normal method and fill the cylinder so that the bottom of the liquid curve (called the meniscus) is even with the 40 mL mark. Put the cylinder back on the scale and record the mass. If you used the tare feature on your scale earlier, you can go straight to calculating specific gravity. If not, subtract the mass of the empty cylinder from the mass of the cylinder plus the sample and use the result in your calculations.
To get the specific gravity of your sample, divide its mass by the mass of an equal volume of water (40 mL in this case). Let’s assume our sample had a mass of 42.5 g. Since we know (considering the above listed assumptions) that water has a mass of 1g/mL, we can assume that 40 mL of water has a mass of 40 g. That gives us a specific gravity reading of 1.063 (that is, 42.5 g/40 g) after rounding up.
It is important that your wort sample be close to room temperature (70 °F/21 °C) when measuring its mass, since the assumed mass of the water you’re comparing it to is based on a room temperature mass measurement. Temperature directly impacts volume, so if your sample is too far above or below room temperature, it will adversely affect the accuracy of your specific gravity calculation.
When putting together your own measuring system, consider the following things: A sample size in the 35 mL to 50 mL range is a nice tradeoff between sample size and accuracy. The larger the sample, the more fine-tuned the result will be (assuming all other variables are the same) . . . but it also means less beer in your bottles or kegs at the end of the brewing process. A sample size of 100 mL is also easy to work with and accurate, but it can be difficult to find a graduated cylinder of that volume with a small enough base to fit on the measuring tray of smaller scales.
Depending on the accuracy of your scale and graduated cylinder, your specific gravity calculations as outlined above may be off by as much as 0.010. But with careful volume measurements and an accurate electronic scale, you can calculate specific gravity with a relative degree of accuracy . . . especially if you just broke your hydrometer.
Dry airlock
Airlocks are essential tools in the vast majority of homebrewers’ fermenting setups, and most of the airlocks out there use water or some other liquid in one configuration or another to allow CO2 to escape from a fermenter but prevent airborne contaminates from getting in. In essence, these water-based airlocks are simple hydraulic check valves. They work great but have some downsides. For example, the liquid can evaporate over time or be ejected during vigorous fermentation, thus rendering the airlock more or less useless.
One way to avoid these downsides is to use a non-hydraulic check valve in place of a standard S-shaped or three-piece airlock. For this project, you can use either of two small check valves outlined below and available from US Plastic (available at www.usplastic.com) in conjunction with a drilled rubber stopper or plastic carboy cap.
For polyethylene terephthalate (PET) plastic carboys, use a drilled No. 10 rubber stopper with a 3⁄8″ polypropylene liquid/gas check valve (US Plastic part No. 64049, $1.04).
For glass carboys of any size, use the appropriate-sized drilled rubber stopper with the same check valve as above. I find that the fit is sufficiently snug to ensure proper operation, but if your stopper hole is a little too wide, apply a small amount of 100% silicone caulk to the check valve shaft and reinsert it in the stopper. For buckets, you can simply insert the check valve straight into the rubber airlock grommet and you’re done.
As an alternative for PET or glass carboys, you can use a plastic carboy cap with a 3⁄8″ polyethylene check valve (US Plastic part No. 64001, $1.69). Insert the check valve into the thinner, taller stem.
Again, I find the fit to be snug as is, but you can caulk this connection if need be.
The nature of check valves is to allow air to pass through in only one direction, so make sure you have the “out” end of the valve facing the outside of the stopper (look for a small arrow on the valve that indicates the direction of flow). Also note that there are several check valves available in the size useful for this project, but most of them have a cracking pressure (the minimum pressure need to open the valve and let out the CO2) that is too high for our purposes. Please use only the two check valves listed above (or do extensive testing on other models before use), or there is a possibility that you could end up with beer on the floor and ceiling in the best case and serious physical harm from exploding glass in the worst case. Do not underestimate the power of fermenting beer.
Although dry airlocks do not exhibit the familiar and delightful *kerplunk* sound as bubbles escape during fermentation, you can tell it is doing its job by the soft *pfft* sound it makes as gas is pushed through it. Also, for you airlock sniffers out there, dry airlocks expel CO2 that has not been passed through the sanitizer/water that is in a standard airlock, thus affording an unadulterated olfactory experience.
Please note that a dry airlock should be used in exactly the same manner as a liquid airlock. It is not a substitute for a good blowoff hose should you require one.
Plate chiller backflush assembly
As competition has increased and prices fallen over the past couple of years, brazed plate wort chillers have grown rapidly in popularity. Their ability to chill wort to pitching temperatures in just a few minutes makes them an attractive addition to any hombrewer’s arsenal of equipment. One drawback to homebrew-sized brazed plate chillers, however, is that they cannot be taken apart for cleaning purposes like plate heat exchangers with gaskets. Without proper cleaning and sanitizing, a plate chiller can become a haven for various contaminates that might ruin an otherwise perfect batch of beer. Thankfully, most brazed plate heat exchangers are small enough to be submerged in a pot of boiling water, which is the surest way to sanitize it.
Enter the backflush assembly, which is very simple and yet very useful tool for keeping the “wort” side of your chiller spic and span. You can buy commercial versions of this handy tool for about $20, but you can make one for about $5.
All you need to “get ‘er done” is a 3⁄4-inch garden hose thread fitting with a hose barb, a 1⁄2-inch female NPT fitting with a hose barb, and a length of standard vinyl tubing.
I chose to work with plastic fittings (US Plastic part No. 63003, $1.51, and No. 62172, $1.04) because they are light and cheap, but you can just as well use brass or stainless steel fittings if you prefer. I recommend using fittings with either 3⁄8-inch or 1⁄2-inch hose barbs. If you have a hot water garden hose connection, consider using hi-temp vinyl tubing instead of the standard stock.
Putting the assembly together is simple. Cut a length of tubing that fits the needs of your brewing space, then simply attach the hose barbs to the open ends of the tubing. In my experience, tubing clamps are not needed but they can’t hurt.
Once you’ve got your wort chilled and in the primary, hook up the backflush assembly between your garden hose faucet and the “wort in” fitting of your chiller and let the water run for a minute or two.
Then connect the assembly to the “wort out” fitting (giving the chiller a true backward flush) and let it run for a few minutes as well. The flush water should run clear after just a few seconds as hop particulate and cold break proteins are pushed out of the chiller. Running it for a minute or more is probably overkill, but I’d rather err on the side of caution. From this point, follow your own normal cleaning and sanitizing procedure.
I recommend you pay close attention to sanitizing, as it is very easy to contaminate a batch of wort with a dirty heat exchanger. The most surefire way to clean and sanitize your heat exchanger is using boiling water to either submerge the whole exchanger or pumping the water through the unit (which is more of a commercial method).
Another technique is heating a large volume of hot water and running it into the wort cooler similar to cooling wort. The temperature of the water leaving the unit is measured and the flow rate adjusted to keep the outlet temperature above 180 °F (82 °C). Once the heat exchanger is hot, the flow rate required to keep it hot is quite low. The unit needs to be maintained for at least 20 minutes at 180 °F (82 °C).
