Yes. Double the amounts for 10 gallons.
How do I decide which to use?
First I put in the water report values.
Then I picked a hypothetical mash/sparge (5g/3.5g) size.
Then I put in the recipe values. Total grain, caramels, roasts, and color.
It’s a dark beer and will acidify your water. You’ve got really
soft water and if you enter your numbers this far it will calculate a mash pH of 5.12, which is a bit on the acid side.
The other thing to notice is that you’re a little shy on Calcium. Yeast likes Calcium. Helps with flocculation.
Given those two things I looked at what raises pH. The choices are Baking Soda and Chalk. Chalk doesn’t dissolve very well, so I used some of both and more of the Baking Soda. I started with small numbers and changed them around until the pH seemed reasonable.
If you wanted a really malty stout, you could leave out the Gypsum and Calcium Chloride. The BU:GU ratio on the recipe makes me think it should emphasize the hops as much as the malt, so I wanted to get the Chloride to Sulfate ratio down to around 1. Gypsum adds Sulfate, Calcium Chloride adds Chloride, they both add Calcium. I started with 1 g of each and was happy with the numbers that resulted.
…on second thought I might bump that to 2.5 g of Baking Soda instead of 2. (I added up the grain weights wrong the last time).