Practical Guide to Calcium Chloride Solutions
The problems with solid calcium chloride were described here in a previous post. A major problem with the solid form is that its strength can vary due to it absorbing moisture from the air. This problem is so bad, that Dow Chemical (a major calcium chloride manufacturer) only quotes ranges of strength for their products. Their ‘anhydrous’ product has only 94 to 97 percent calcium chloride by mass (it should be 100 percent) while their ‘dihydrate’ product has 77 to 80 percent by mass (it should be 75.5 percent). So you can see that knowing how much calcium chloride you are actually adding to your brewing liquor is difficult!
Creating your own calcium chloride solution is a better way to know how much you are actually adding to your liquor. It’s really not that difficult to create your own solution, measure its strength, and use it.
The first thing to be aware of: combining calcium chloride and water produces a LOT of heat. It is a highly exothermic reaction. It is possible to raise the temperature of the combined mixture by 100C or 180F when creating a strong solution. This means you must start with cool or cold water. Do not use hot water or it could boil!
For brewery use, a strong solution may not be ideal since they become more viscous and minor errors in dosing produce greater error in the calcium chloride dose. Something between 10 and 30 percent solution may be more practical. To provide an idea of how much solid calcium chloride to add, about 120 grams of ‘near-anhydrous’ solid per liter of water produces about a 10 percent solution (roughly 1 lb/gal in US units). If the dihydrate form is used, the amount of the solid would need to be about 1/3 greater than for anhydrous. Since we can’t rely on the ‘true’ strength of the solids, we have to mix up a solution and then measure its specific gravity (SG) to figure out the solution’s true strength. It’s best to use relatively pure water for the solution. RO or distilled water is recommended. That avoids adding other unknown ions to the solution.
Once a solution has been mixed up and fully dissolved, it is important to cool the solution to room temperature before measuring its SG. Room temperature is generally considered to be between 20C & 25C (68F & 77F). Since upper measurement limit of typical brewing hydrometers is typically 1.180 or less, we are limited to measuring the SG of 20 percent or weaker strength calcium chloride solutions with a hydrometer. For stronger solutions, we have to use an accurate volume measure like a laboratory graduated cylinder and a precision scale to measure SG. Measure the tare weight of the empty cylinder and then fill it with a precise amount of the solution, say 100 mL. Weigh the filled cylinder and subtract the cylinder’s tare weight to determine the weight of the solution it contains. If the weight is in milligrams (mg), the calculation is easy. For example, the weight of the solution was measured at 120 milligrams, then the SG is: 120mg divided by 100 mL, which is 1.200.
With that SG, we can calculate the percentage strength of the solution with this equation:
% strength (w/w) = – 36.158*(SG)^2 + 183.75*(SG) – 147.47
Yes, that equation may be a little difficult for some users, so Versions 3 and above of Bru’n Water software include the strength calculation above and the ability to employ calcium chloride solutions to deliver a more accurate and reliable calcium chloride dose to your brewing liquor. Don’t be left wondering if your calcium chloride solids have absorbed moisture. Convert to liquid!