Most of the literature I read talks about maximum ppm for various ions.
Bicarbonate tends to be suggested up to 250 ppm, with an absolute max of 300. However, the famous Dortmund water has 550.
Calcium tends to be recommended up to 150 ppm. However, Burton on Trent has 295, Dortmund has 250, and Vienna has 200.
Residual Alkalinity starts getting red and angry at me in Palmer's calculator as soon as it hits 300.
The problem I routinely run into when trying to build water profiles for very dark beers (anything above ~35) is that I have to break the Bicarbonate and/or Residual Alkalinity "caps" to build the proper theoretical water profile.
For example, for a beer with an SRM of 39, I get a min RA of 353 and a max RA of 412 listed. To hit the minimum Residual Alkalinity, I have to use at least 475 ppm of Bicarbonate.
What have I always done? Used caution. I've always refrained from breaking the theoretical upper limits on RA and HCO3.
Does anyone have any better data on how to create an appropriate water profile for very dark beers?
I'll throw these questions I've always wondered about as well:
When I'm calculating ppm for Calcium, should I go for a minimum of 50 for the actual volume of the wort, or just the mash volume? My assumption has always been that I'll need to hit 50 ppm of Calcium for the 5-7 gallons of wort rather than just the mash volume.
If I am using an infusion in my mash, should I split my salts? For example, if 60% of my mash water is in during a protein rest, then 40% gets added 20 minutes later, should I use 60% of my salts in the first batch of water, then the remaining 40% in the second? My assumption has always been that I should split the salts up, so I've done so.