The chloride-to-sulfate ratio in your brewing liquor influences the perception of your beer. Adding chloride to your water, usually in the form of calcium chloride, makes your beer more “rounded” and accentuates the malt. Adding sulfate, usually in the form of calcium sulfate (from gypsum), accentuates the hop bitterness. We’ve designed an experiment to test if this is true, if you can adjust this ratio in finished beer and which ratio works best in an IPA (or other hoppy ale). The last one is the biggie, here. The first idea is well-accepted and there’s anecdotal evidence that the second is true.
Brewing the Base Beer
The experiment is simple, brew 5.0 gallons (19 L) of IPA with a 1:1 chloride-to-sulfate ratio, then adjust the ratio as you bottle. To do this, on brewday, start with distilled water, RO water or tap water that has been diluted with distilled water to 25 ppm bicarbonate or less. Then, add calcium to your water by adding both calcium chloride and gypsum. For 10 gallons (38 L) of water, add 4.0 g (a little over 1 tsp) of calcium chloride and 4.0 g (about 1 tsp) of gypsum to get to 50 ppm calcium, with a 1:1 chloride-to-sulfate ratio. Make the wort, ferment it and get ready to bottle.
When you bottle, you will bottle 1.0 gallon (3.8 L) of beer at the existing 1:1 chloride to sulfate ratio. For each subsequent gallon (3.8 L) you bottle, you will add gypsum to yield bottles at 1:2, 1:3, 1:4 and 1:5 ratios, respectively. Here’s how to do that. Bottle the first gallon (3.8 L) as you normally would, and label these bottles with a “1.” Then, add 1.5 g of calcium sulfate to the remaining 4.0 gallons (15 L) of beer. To prevent foaming, wet the gypsum before adding it (see below for more). Stir to dissolve the gypsum into the batch, but not so much that you splash and aerate the batch. Let the beer sit for 2 minutes (so the dissolved gypsum evens out), then bottle the second gallon. Label these bottles with a “2.”
For the third gallon (3.8 L), add 1.0 g of gypsum and label the bottles “3.” For the fourth and fifth gallons, add 0.75 g and 0.33 g of gypsum, respectively. Label the bottles “4” and “5,” as appropriate.
The Solubility of Gypsum
Measuring the tiny amounts of gypsum required could be a problem. One way around this would be to make a known gypsum solution and add this. However, the solubility of gypsum is around 2.4 g/L in pure water. As such, you’d need add a total of just less than 2.0 qts. (2.0 L) of this solution to the beer by the end of bottling. So, when adding gypsum, just do your best to measure out the small amount. Then, wet it into a slurry. This will still likely raise some foam (and lower your level of dissolved CO2) when you stir it in, but it won’t dilute the beer as much. Incidentally, the solubility of calcium sulfate increases in colder water, contrary to how most solids behave, so don’t try to use hot water to make the slurry. The solubility of gypsum is increased in acidic solutions, so it’s possible that you could make an acidified known solution of gypsum, but then you’d also be dosing the beer with whatever acid you used.
If you’re making an extract beer, you won’t know the initial chloride-to-sulfate ratio in the dissolved extract. You can still try the experiment by brewing an extract beer using distilled water to dissolve the malt extract. You can use water treated with an equal amount of calcium chloride and calcium sulfate (gypsum) if you do a partial mash. Add the same amount of gypsum as called for above. You won’t know the exact ratio of your beers, but you will have a series of beers with increasing percentages of calcium sulfate.
You can brew any IPA you’d like, or any other hoppy beer that you like, for this experiment. Here’s the recipe James and I will be brewing, if you’d like to join us. (Ignore the water recommendations in the recipe, obviously, and follow the experimental protocol above.)
We’ll post a form later to fill out, but basically the analysis will involve tasting the beers and giving your impressions of each. We’ll collect the results of participants through this Halloween (Oct 31, 2013).
There are a couple criticisms that could made of this experimental design. Although the chloride-to-sulfate ratio varies among the experimental treatments, so does the level of calcium and carbonation. The higher numbered beers will have more minerals dissolved in them and (likely) less carbon dioxide from foaming when the gypsum is stirred in. This could be corrected by brewing five separate batches of IPA. Of course, that’s a lot more work and we think the experiment will still provide valuable information (and perhaps inspiration to run larger scale experiments in the future).
You can hear James and I discuss this experiment on his Basic Brewing Radio podcast, September 25th, 2013 episode.