Many homebrew recipes are scaled down from commercial-sized batches. And occasionally you’ll find that the amount of certain ingredients or additives required at the homebrew scale is small, or even tiny. To make matters worst, the ability for homebrewers to accurately measure small weights and volumes is frequently limited. Even scaling a regular, 5.0-gallon (19-L) homebrew recipe down to a 1.0-gallon (3.8-L) test batch sometimes results in certain additions of hops, other spices or mineral salts to be smaller than can be easily measured.
Most cooking-type scales only measure down to 1/4 ounce when set to English units and 5 g when set to metric. (And note that these are close, but not the same. A quarter ounce is 7.1 g.) More accurate scales or balances are available, but they are generally pricey. Along those same lines, measuring small volumes of liquids (for example hop extracts) can be problematic for homebrewers who may have only kitchen measuring cups — or teaspoons and tablespoons — available.
Measuring Soluble Substances
In the case of solids or liquids that are soluble in water, there is a simple workaround. If you need to measure out the weight of a solid or the volume of a liquid that is below the resolution of your scale or measuring cup, making a known solution will help. Basically, you dissolve a known amount of the substance (more than you need) into a known volume of liquid. Then, you dispense a portion of that volume, which contains the correct amount of the dissolved substance.
Let’s say you’re brewing a small batch of beer and it calls for 3.5 g of calcium chloride to be added to your brewing liquor. But, the smallest increment your scale measures is 5 g. The first step would be to measure out the smallest amount of calcium chloride that you are confident your scale can weigh accurately. If the smallest increment is 5 g, you could go with 5 g. Or, you could pick a larger amount. (Calcium chloride is cheap.) For the sake of example, let’s say you weighed out 10 g.
Your next step is to dissolve that solid in a volume of water. You need the solution to be dilute enough to completely dissolve the solid, but you don’t want to mix up a needlessly huge volume, either. In this case, lets say you dissolved 10 g into 100 mL of water, yielding a solution of calcium chloride with 1 g per every 10 mL. Adding 35 mL of this solution to your brewing water would add the 3.5 ml of calcium chloride called for.
This method is only as accurate as your scale and measures of volume are. Be aware that kitchen scales and measuring cups are not scientific tools. They should be close enough for any situation in homebrewing, but if you want to be more accurate, get a triple beam balance and a set of graduated cylinders (10 mL and 100 mL, and maybe one larger size, of needed). A regular classroom-type triple beam balance will let you weigh items to 0.5 g and a decent 10 mL graduated cylinder will let you measure as little as an 0.1 mL (+/- about 2%). This will be overkill in almost any homebrewing circumstance.
The method above only works for things that are completely soluble in water. And for things that are expensive or perishable, making a dilute solution may be costly or wasteful. Still, it will work for any mineral salt or sugar, and could work for some spices. (And you also have the option of making an alcohol extract of spices with vodka.)
Insoluble Solids — A Quick and Dirty Method
For solids that aren’t completely soluble in water, like hop pellets, there’s a “quick and dirty” way to measure out small amounts. It is accurate enough for most homebrew situations, especially if you know you have a little leeway in your measurements.
Let’s say your recipe calls for 3/5 oz. (or 0.6 oz.) of hop pellets and you don’t have a scale handy. But you do have a 1.0 oz. packet of hops that you to believe to be reasonably close to the correct weight. Pour the pellets onto a flat surface and push them all together in a small hill. Now, as accurately as you can eyeball it, divide the hill into two equal parts. Now you have two piles, each at 0.5 oz. If 0.5 oz is close enough to 0.6 oz. for your liking, then you are done.
If not, take one of the piles and divide it in half again. Now you have one pile at 0.5 oz. and two piles at 0.25 oz. Dividing one of the smallest piles equals yields piles of 0.5 oz., 0.25 oz., 0.125 oz. and 0.125 oz. Combining the 0.5 oz pile with one of the 0.125 piles is 0.625 oz. If that’s close enough, your done. If not, keep dividing one the smallest piles until the sum of one set of piles is close enough to your target for your taste.
For measuring out small amounts of mineral salts, you can use a dark plate and a razor blade or credit card to separate the piles. Just be sure that nobody is likely to walk in on you unexpectedly — unless you are starring in your community theater’s production of Scarface.
The accuracy of this method depends on your initial measurement and how good you are dividing little piles exactly in half. In a pinch, this should do fine in any homebrew situation. If it seems too error prone for you, invest in a triple beam balance — which should be more than sufficient in any homebrew situation.
Volumes of Small Kitchen Measures
The volumes of various kitchen measures. (Note: These things can vary dramatically in how much they actually contain. The numbers below are what they should contain.)
one cup = 8.0 fl. oz. (240 mL)
half a cup = 4.0 oz. (120 mL)
one jigger = 1.5 fl. oz. (44 mL)
one fluid ounce = 2 Tablespoons (30 mL)
one Tablespoon = 3 tsp. (15 mL)
one teaspoon = 5 mL
one drop of water = approx. 0.05 mL (or about 20 drops/mL)