Epsom salts to get to 300ppm of SO4?
Quote from the site you linked:
Magnisium- recommended 10-30, Levels higher than 125 ppm have a laxative and diuretic affect.
gypsum gets you most of the way there, epsom salts can be used to give you a boost. I thought i made that clear. But since i seemed to have left it a little questionable I'll work out an example. . . If I'm targeting 150 ppm Ca, 300 ppm SO4, 100 ppm Cl for a pale beer (like an IPA with a SRM around 6-8) and all I have available to me is chalk(which I won't use here), Baking soda, CaCl, Gypsum, Epsom salt, and canning salt. I'm likely to build my water from RO for a 10 gallon finished batch of beer like this without using Epsom salts or canning salts:
3g Baking Soda (NaHCO3) - to build some alkalinity in the beer
39g Gypsum CaSO4 - adds Ca, a vital yeast nutrient, and SO4, which accentuates hops
15g CaCl2 - adds Ca, again vital yeast nutrient, and Cl, which accentuates a rounder more malty taste
My Mineral profile now looks something like this (assuming RO water is free of minerals, which I know it's not but it mostly is and we will work off the assumption that it contains no minerals to start with):
Ca: 183 ppm
Mg: 0 ppm
SO4: 303 ppm
Na: 12 ppm
Cl: 100 ppm
HCO3: 30 ppm
Alkalinity 25 ppm
Okay, so I will walk you through how I built this (any all the rest of my water). I always start with alkalinity. For a pale beer it needs to be low. I can do this 2 ways; with Chalk (CaCO3) or Baking Soda (NaHCO3). Since I know that for this instance I'm going to have plenty of Ca, I don't need to add any by using Chalk. I choose to add 3 grams of baking soda. This adds Na and HCO3 (or alkalinity) to my water. The Na can add a roundness and accentuate malt flavors in beer, but not at 12 ppm that we have here. For a pale beer we want between 0-50 alkalinity. The roll of alkalinity is to buffer the mash pH, which can become very acidic in the presence of toasted, caramel, and especially roasted malts. Choose this level based on the beer ingredients your using. Next I want to work on building up SO4 and Cl (It doesn't really matter which I do first). Gypsum is ALWAYS first choice for adding SO4 to water, so 39g gypsum(CaSO4) goes in to get us in the neighborhood of 300 ppm SO4. This addition has also added a significant amount of Ca to our water. Next we add 15g CaCl to get to 100 ppm Cl. At the same time, we have again added Ca to your beer.
At this piont, for this example without using Epsom salts or canning salt I'm done. It would probably be okay but there are a few things I would nit pick at here.
1) That's really too much Ca
2) Mg is an important yeast nutrient in small amounts (10 -20 ppm)
So what I propose is to take out a small portion gypsum (CaSO4) and build SO4 back up with Epsom Salts (MgSO4). At the same time, I can take some CaCl out and build the Cl back up with some Canning salt (NaCl). It would look like this:
3g Baking Soda
32g Gypsum
10g CaCl
10g Epsom Salt
4g Canning Salt
Which results in a water profile that looks like this:
Ca: 141 ppm
Mg: 14 ppm
SO4: 302 ppm
Na: 34 ppm (I don't like to take this much higher in a beer designed to be highly bitter)
Cl: 100 ppm
HCO3: 30 ppm
Alkalinity: 25 ppm
Maybe it's my personal preference but this looks better to me.
Lastly a few notes about this. These numbers are calculated from 19 gallons of total water, which is about the amount I have to use on brew day to create 10 gallons of finished beer. Each salt additive needs to be split proportionately between the mash and the boil. I wanna take a minute to note that the amounts of SO4 and Cl aren't as important as the ratio. This would create a 3:1 ratio. . . accentuating a highly bitter beer. The question you should be asking then is why use such high numbers? In reality, I don't think I'd go 100 ppm Cl to 300 ppm SO4. the problem changes a little (but not much) if I drop the Cl down to 60 ppm (which is a 1:5 ratio of Cl:SO4, which I have done before). Na (Soduim) can cause a beer to seem more rounded or malty sweet. . . 34 ppm is probably insignificant to that but I wouldn't push it much farther unless that was my intent (Palmer claims the effect takes place between 70 ppm and 140 ppm). Building water isn't an exact sciences. . . there are more variables than what we can account for.
Hopefully that clears up more questions than it created.