Dark grain addition timing

My tap water here is fairly soft so I find my darker beers come out a little astringent. I'm about to brew a porter tonight that has a couple pounds of various dark malt in the recipe. I ground them separate and I'm debating on adding them later in the mash or tossing them on top as I start my vorlauf. Does anyone do this with dark grains, add them later in the process?

Yes. I cold steep my dark grains 24 hours or more before I brew and then add the liquid from the cold steep into my boil during the last 10-15 minutes just to kill the lacto and whatever else was living on the grain.

But you're brewing tonight, so you don't have enough time to cold steep. I like your idea of tossing them in the mash after vorlauf, or really anytime after conversion is complete. The dark grains had affect your mash PH so you remove them from the mashing process. Good idea.

Let us know if you get a less astringent porter.

I also have soft water and let my dark grains rest over night in cold water. I do a decoction mashout, so I add the entire dark mush when I stir after the decoction. Works well for a smooth dark brew.

I do decoction mash outs too. Ever since I brewed my first pils with three decoctions I feel like it just makes sense to mash out that way. I brewed my porter tonight and added the dark grains during the vorlauf. I probably circulated more than I normally would but I waited to sparge until my wort started to get dark. Seemed to work well but I guess time will tell.