Adding 10mL to all samples makes sense. So, my plan is to make 2 stock solutions....
Sulphate = 2.00g Gypsum + 2.27g Epsom into 1000mL = 2001ppm SO4, 466ppm Ca, 224ppm Mg
Chloride = 4.5g CaCl2 into 1000mL = 2002ppm Cl, 1132ppm Ca
I plan on using it to test 2 x 8L brews - a 29IBU Best Bitter...