adding dark malts to the vorlauf and corresponding mash thickness

I'm not into water adjustments and use spring water which is hard and great for stouts, or so I'm told. All my grains go into the mash tun with no problems.i would think if you did not mash the dark grains and just poured vourlof wort over them, you would not gain much if anything. If you have poor water for brewing then perhaps others can help.

 

If you wanted to, you could add some, on a quarts per pound basis that is consistent with your original mash. I don't see it having a big impact on anything I brew, where dark grains rarely would exceed 10% of the grist weight, but maybe others think differently.

 

Hold on, I'm confused by this. Are you saying that:

A) you're waiting until vorlauf to add dark malts because you want them in the recipe but don't want them to lower the pH too much; or
B) you want to lower the pH but don't want dark malts in the recipe, and at vorlauf you're thinking they'll affect the pH but not the flavor

Either way I've never heard of this being done. Does it work? I can't imagine B would work. But in A would you get enough flavor from the malt with vorlauf alone?

 

Spring water can be hard or soft. It depends on where it comes from. Perhaps you know your particular spring water is hard.

Regarding stouts (and their acidic grain bills), it's not hardness that's useful, it's alkalinity, which counteracts the acid contribution from the grains to help get the mash pH into the right range.

 

Go @VikeMan , should a said my water is harder than hell and very alkaline , to the point where I gotta add acid to my greenhouse water so my flowers grow well, nice catch.

 

If you want the full flavor contribution from the dark grain, I would suggest mashing them with the rest of the mash for the full duration and adding a little baking soda if you think the ph will be too low.

btw: caramel malts can drop the mash ph even more than highly roasted malts...so don't think this only applies to stouts

 

Sort of, but to clarify... Pound for pound, no, the higher roasted malts contribute more acidity than C-Malts. But "per unit of color change," yes, C-Malts are more acidic than, say, black patent malt.

 

I don't get the PH thing either - I'm no chemist (hell, I leave my tap water alone for my brews and don't ghave a problem) I'm thinking the 'why' is C) wants to get the color from dark roast malt without the flavor or PH issue(?)

 

You're just wasting grains. You need to have the PH correct during the mash. Adjusting after has no benefits. You also don't worry about the ph of the water, only during the mash. Skip down to why ph matters.
http://beersmith.com/blog/2015/05/07/mash-ph-and-why-it-matters-for-all-grain-beer-brewing/

 

I guess I don't understand your initial question.