Measuring Specific Gravity

Homebrewing can be as precise as you want it to be. But even if you're brewing by the seat of your pants, you still need to measure things: temperature, volume, weight/mass, pressure, and density (as specific gravity). This last one is important since it tells us where our batch started, its potential for ethanol creation  and where/when it is finished.

The Gravity of the Situation

Specific gravity is the ratio of the density of a given liquid to a reference liquid, usually water. This value is expressed as a number to three decimal places, and each 1/1000th is called a point. Water has a specific gravity of 1.000 and a solution registering 1.025 is 25 points denser.

If you've ever used brewing software like BeerSmith or Brewer's Friend, you'll see that it lists a PPG (points per gallon) value for malts and adjuncts. This means that using brown sugar or caramel 20L malt will add X points of sugars to your wort per gallon of water.

These programs calculate your starting gravity (SG) using these PPG values. This is sometimes referred to as original gravity (OG). It then extrapolates how many of those points can be consumed by the yeast and gives you an expected final gravity (FG) as well as an expected percentage of alcohol by volume (ABV).

These are calculated values based on the grist bill you input. But that might not be the gravity you get. If your mash is too warm, your SG/OG will probably come in a little low.  If you lost count and put in an extra pound of brown sugar, your SG/OG will come in high. (True story: I built a recipe with a pound of honey, but input the same PPG value as LME. The actual SG/OG came in 30 points high at 1.084. Oops!)

Displacement: Glass Hydrometers

Triple-scale (left) and
FG hydrometers

For the homebrewer, there are two methods for measuring specific gravity: refraction and displacement.

The simplest, most direct way to measure specific gravity is by displacement. Weighted glass hydrometers are calibrated to float at a certain level in water at a certain temperature. You read the gravity by looking at the bottom of the meniscus in a sample and read the value on a paper scale inside the hydrometer.

The most common hydrometer is a triple-scale, which covers a wide range of gravities (mine goes from 0.982-1.060) and has scales in points as well as brix and potential alcohol. This is the kind that often comes in beginner homebrew kits. There are also more sensitive hydrometers that have narrower scales.

PRO:

• Cheap - The triple-scale costs only $7, which is a good thing. More sensitive FG versions can run up to $30.
• Reasonably accurate - For the money, a hydrometer is hard to beat in the accuracy department. You can get much better accuracy in a lab-grade device, but these are well over $100. 
• Versatile - The triple-scale can be used for SG and FG readings of beer and wine.  

CON:

• Low sensitivity and hard to read - This is my biggest knock on hydrometers, the triple-scale in particular. The broad scale means the markings are pretty close together, so it can be hard to read. I spend a lot of time staring at the meniscus trying to figure out if it's 1.044 or 1.046. I bought a second hydrometer with a much shorter range (0.990 to 1.020) to measure FG. If nothing else, it's much easier to read. 
• Waste of wort - It takes a fair amount of liquid to float them. Not a big deal with pre-boil wort since you can just pour it back into the pot, but it can be a waste of finished beer. 
• Fragile as all get-out - They are very fragile, and there's many a homebrewer that's broken one. HomeBrewTalk has an Official Broken Hydrometer Count thread going, and the grim tally is over 2,200. I did say they were cheap, so replacing won't pinch your wallet.
• Sensitive to temperature - Hydrometers are calibrated to water at a certain temperature, usually 60F. If your sample is considerably warmer or colder, the reading will be off. There are plenty of online calculators to correct the reading, but it's another step to take and you'll need a thermometer.
• Scale can drift - I did say they were accurate, and they are pretty good considering they cost under $30. But the paper scale inside can shift, especially if it's handled roughly. A 1.040 now might look like 1.036 if the scale slides down.  

Displacement: Electronic Hydrometers

The Beer Bug uses a float to measure
specific gravity from inside
your fermenter (Photo: MoreBeer)

In recent years, some clever folks have come up with electronic hydrometers that take readings constantly inside the fermenter. The Beer Bug and the Tilt float in the wort and tilt as the gravity changes. They transmit their data to a nearby computer, so you can see minute by minute how fermentation is going. These new devices eliminate all of the cons of glass hydrometers, but they have their own drawbacks.

PRO: 

• Easy to read - These are the digital watch to the glass hydrometer's sundial.
• Continuous readings - If you just love data, you can see how fermentation is going by the minute.
• Won't disturb primary - It takes its readings inside the fermenter, and you can check on its progress remotely. 
• Saves beer - No need to draw off samples, so you won't waste any beer.

CON:

• Expensive - $120-140 new, or what you'd spend on a handful of glass hydrometers.
• Requires some technical proficiency and extra electronics - These devices need another computer/tablet/smartphone to record data, and it'll be up to you to set it up. If you have an old smartphone with Bluetooth, great! Otherwise, you'll need to shell out for a compatible device.

Refraction: Analog Refractometer

My analog refractometer

The other method is to measure how much light bends - or refracts - as it passes through a liquid sample. Refractometers only need a few drops to get a reading, so they work great for checking the gravity of your mash or wort while boiling.  

OG of 1.057

PRO: 

• Easier to read - The scales can be pretty tight, but much easier to see where the blue stops than determine where the meniscus is in a turbid wort sample.
• Automatic temperature correction - The sample doesn't need to be room temperature, though I suspect it cools down very quickly when dropped onto the prism.
• Saves beer - Just needs a few drops of wort.
• Relatively inexpensive - They can be had for $20-30, though nicer ones will cost more
• Easy to calibrate - Add two drops of distilled water, then turn the adjustment knob or screw until it reads 1.000

CON:

• Cheap ones aren't very accurate - This is simply "you get what you pay for." I wouldn't be surprised if cheapo models need  constant adjusting. For what it's worth, I bought mine off of Amazon for $25. The picture on the right is an OG reading I took from my amber ale. It matched the expected value form Brewer's Friend and was pretty close to triple-scale hydrometer.
• Can be knocked out of calibration - Dropped it? The you'll want to re-calibrate. That said, I imagine they're far more durable than glass hydrometers.
• Wider scales are hard to read - Mine goes from 1.000 all the way up to 1.130 (or 0-30+ brix). This is fine for wine making, but it's is ridiculous for home brewing. A scale topping out at 1.060 with a more sensitive prism would be much easier to read.
• Dissolved solids make for fuzzy readings - Refractometers work best with simple sugars in solution. Wort is more complicated, sugar-wise, so readings can be a little off. Samples with any bit of cold-break proteins will make the line fuzzy and hard to read. 
• Alcohol skews readings - If you're sampling after fermentation has started, the ethanol will distort the readings. You'll need to use a calculator to correct the readings. 

Refraction: Digital Refractometer

Hanna digital refractometer
(Photo: MoreBeer)

These are laboratory-grade electronic devices. Definitely the most accurate tool, but you will pay $$ for it.

PRO: 

• Easy to read - Spits out a number on a digital display.
• Precise - Readings are +/- 1 point.
• Saves beer - Just needs a few drops of wort.

CON:

• Expensive - The cheapest one I've found is $200 from MoreBeer, and it only displays brix, which means you have to convert it to points. Meters that will display points go for $350-450. IMHO, these are overkill for home brewing, but hey, it's your money!

Which is Better: Hydrometer or Refractometer? Yes!

As we've seen, both methods have their drawbacks. You can stick to using one or the other, but I've embraced the notion of using both by playing to their strengths and using the best tool for the situation.

Refractometer for Pre- and Post-Boil, OG

Since there's no alcohol yet, I don't need to adjust my mast or wort readings. I can also get a reading quickly, which is handy if you're trying to boil down to your OG target. It can take a while to cool down a sample jar's worth of wort to get a hydrometer reading.

Hydrometer for Fermentation, FG

Triple-scale (left)
FG hydrometer (right)

Once alcohol is in the solution, the refractometer is at a disadvantage. I don't want get a reading and then convert it, so the hydrometer is the way to go. The best choice, however, isn't the triple-scale but a hydrometer specifically for FG. While they are a bit more expensive ($15), they are considerably more sensitive and easier to read.

I put my FG hydrometer next to my triple-scale with 1.000 marks lined up to show you the difference in ranges. The triple-scale covers 54 points (in two-point increments) in the same space as 10 points (in one-point increments) on the FG hydrometer. Since I only need to be accurate to one point, the FG hydrometer is much easier to read.

It will take a fair amount of beer to float the hydrometer, and you can't pour it back when you're done. But you can give it a taste. And if you have a carbonation cap and an empty plastic soda bottle, you can blast carb the sample to see how it tastes when it's all nice and fizzy.

Citizen Science with a Free Water Test

A researcher from my alma mater is part of the Showerhead Microbiome Project, which is enlisting people to swab the insides of their showerheads to see what lurks within. I thought it was quirky but interesting - I've always wondered what that gunk was - so I signed up. Last week, my collection kit came in the mail. It included a collection swab, nitrile gloves, and some water test strips. Cool, I get to profile my tap water!

Science!!

After swabbing the showerhead (which was cleaner than I expected), I held a 5-in-1 test strip under tepid water for a few seconds. I noted the values for total chlorine, free chlorine, total hardness, total alkalinity and pH, then repeated the process with a second strip to record nitrate and nitrite levels. The third strip checks for iron, so I had to add a small amount of a buffering powder to a vial then dunk a test strip.

I sent the results and swab in, and I hope to find out what's living in my showerhead. Meanwhile, I have a decent profile for brewing.

pH: 6.8
Total Alkalinity: 120 ppm
Total Hardness (CaCO3): 15 grains per gallon = 257 ppm
Free Chlorine: 0 ppm
Total Chlorine: 2 ppm
Nitrite: 0 ppm
Nitrate: 2 ppm
Iron: 0.15 ppm

The water is a bit more acidic (7.7) and slightly harder (7.5 grains) than the average reported by Arlington County. Many all-grain brewers here just grind up a Campden tablet to neutralize the chloramine and mash away. I use some distilled water for partial mash batches, but this profile is pretty good for mashing (minus the chlorine). That said, I really ought to check the pH of my mash. This is all new to a mostly extract brewer. :)

The other cool thing is that these test strips even exist. I plan to get some test strips to test how well my big carbon block filter does with chlorine and minerals.

National Homebrew Competition 2017 - Packing it In

I finally finished my rye amber ale and bottled two more entries for the National Homebrew Competition. Now on to the packing. I'd been reading up on the best ways to ship bottles, and came up with what I think is an excellent packing method. Here's how I packed my eight bottles for shipment to Austin.

The Supplies

NHC entries and shipping supplies

It takes a lot to pack eight bottles of beer to fly (more on that later). I used:

• Cardboard box (12" x 9" x 12")
• Bubble wrap (~4' of wrap with long, narrow bubbles; smaller piece with larger pillows)
• Fragile labels
• This End Up labels
• 1-gallon zip-top storage bags
• Reinforced kraft paper gummed tape
• Fold-top sandwich bags 
• Rubber bands
• 13-gallon kitchen trash bag
• Newspaper

I'll explain my materials choices as I go through my steps. I already had most of this stuff on hand. The only things I bought specifically for this shipment were the Fragile and This End Up labels.

The Bottles

I put my entries in clean bottles with no raised glass or labels. I tried to use different caps for each entry to keep them straight, but I only had two colors of blank caps. I cut out the labels and placed each one in a fold-top sandwich bag, then attached it with a rubber band. 

Entry labels wrapped and banded

The bag will keep the label dry in case a bottle leaks. Some people recommend putting the label in a zip-top bag, but that seemed like overkill ... and I had a bunch of fold-top bags to get rid of.

Entries wrapped in zip-top bags

Each bottle was then placed in a gallon zip-top storage bag. I forced out the air to make boxing easier. This will contain any leaks/breakage, helps the stewards find which bottle is leaking and provides a teeny bit of padding. Some other folks recommend freezer bags or even heat-sealed bags, but again I think that's overkill.

The Box

Newspaper lining the bottom of the box

It just so happens that the box Petco ships my cat food in will fit eight 12oz bottles easily, maybe 10 if you're careful. I kept one that didn't get too beat up bringing CellarCat her tins of Fancy Feast. I took one section of the local paper and placed it in the bottom. I just laid the section in flat rather than crumple it up. This might not be truly necessary, but I felt better having put in some extra cushioning.

Kitchen bag liner

Next, I added a kitchen bag. This is to prevent any leaks from getting to the box itself, which can weaken it and/or draw the attention/ire/wrath of the carrier. 

Bottles separated by newspaper

Now, the bottles go in. I then wrapped a folded length of newspaper in a serpentine fashion around the bottles. Two pieces are in a sort of U-shape around six bottles, while a third is simply folded to fit between the two bottles on the far right. This way I can prevent glass-on-glass contact while using a minimum of material. (The stewards really appreciate that.) It looks loose at this point, but that's fine. We'll use other packing material to tighten things up.

Wrapping up the liner...

... and inserting the bubble wrap.

I loosely wrapped up the top of the liner bag, then slipped the bubble wrap between the bag and the box wall. I had saved up a durable bubble-wrap that used relatively long and narrow bubbles. It slid in to place easily and snugged up the contents. I then placed a few larger bubble-wrap "pillows" on top to fill space. You want the inside to be overfilled, but only slightly.

Filler "pillows" on top

I folded the top flaps down and they didn't close completely, which is how I knew I had filled the space properly. A little light pressure closed the box up neatly.

Taping it Up

I prefer to use reinforced kraft-paper tape for shipping. Plastic tape is fine, but if paper tape is good enough for the likes of Amazon and Petco, it's good enough for me. This tape uses a water-activated glue, and a few sprays of water from a bottle does the trick. It's a bit harder to work with since it doesn't stick immediately, but the adhesive sets up strong. You're effectively gluing the box shut.

If you're reusing a box, make sure it doesn't have any holes or ripped edges. Smaller holes can be patched and flap creases can be repaired, but it's not worth the effort to completely rebuild a box. This box is in great shape, but I added some reinforcing to the short edge along the bottom.

The Weigh-In

The AHA recommends paying for UPS or FedEx shipping online then dropping off the package, probably to avoid uncomfortable questions about what you're shipping. To do that, you need the box dimensions and weight. I put the box on my kitchen scale and it came out to 11.3 pounds. I guesstimated around 10 pounds, so not too far off.

11.3 pounds

I plugged the data in to FedEx and shipping would be ... $78 for 2 Day Air. Yikes. Unfortunately, life got in the way and it was too late to ship via ground. That would've been maybe $15. So, if you're shipping entries, plan ahead!

All dressed up and ready to ship!

I put the shipping label on top (using plastic shipping tape) and slapped on five Fragile labels and two This End Up labels. I also wrote "Samples for Evaluation" on the shipping label, as recommended by AHA.

As I picked up the box, I gave it a little shake to see how well I packed it. Nothing moved or clinked. It also felt a little bottom-heavy, which makes it more likely to ship right-side up.

I dropped the box off with FedEx without incident on Monday afternoon. The box arrived at Austin Homebrewing just after 8am Wednesday, easily beating the AHA deadline and FedEx's own 4:30pm service guarantee. Nobody has called me about broken bottles, so it seems all eight made it just fine.

Homebrew Hack: Water Bottle as Beer Bottle Bath

I've been scrubbing commercial beer bottles for competition entries. The hot PBW soak does wonders on paper labels, but plastic ones are a different story. Some peel off easily enough, but the glue left behind is stubborn.

I had one 12oz bottle that I wanted to soak in rubbing alcohol, but couldn't find a container that was the right size. Everything is either too big or too small. Then I found a drinking water bottle in the recycle bin. A quick hack with a paring knife turned it into a bottle bath.

Water bottle turned bottle bath

The plastic bottle is just a bit wider, so I only needed a few ounces of alcohol to submerge the sticky part. It did what I needed it to, and it did it pretty well. I couldn't get all of the glue off, but it was clean enough. Then after all of this, I see the bottle has a defect in the glass. See the light oval shape in the middle, just above the reflection of my smartphone? That's a void in the glass. This one went right into the recycle bin.

All that cleaning, only to find a defect.

Moral of the story: Check your bottles for defects before you waste a lot of time cleaning and sanitizing.