Stouts/Porters/Dark Lagers Perceived Off Flavor

[BugAC]

I've got an oatmeal stout planned to brew this saturday, and as i'm thinking about it, i want to avoid some things i've been noticing in a few dark/black ales/lagers i've had recently. I was drinking a czech dark lager the other day. And while it was a good beer, i found that it had a lingering harshness on my tongue that didn't seem to go away. I made it through about 3/4 of the beer before my palate was fatigued and i poured it out. I find this to be a problem i have with some stouts as well.

My question, is what could be causing this flavor/layering on the palate, and what steps could i take to minimize it? I don't believe it's an ingredient issue, but maybe an issue with water profile, or maybe i'm tasting some astringency from too hot of a sparge. I know the description i'm giving for the flavor i'm picking up is vague, i'm just wondering if others get the same perception from black ales/lagers like i do?

 

[AlexKay]

Astringency is like sucking on a tea bag, if that helps. And comes about from too-hot and/or too-basic water in contact with the grains.

 

[kevin58]

Dark malts can impart an astringent character. Try adding your dark malt toward the end of the mash.

 

[rmr9]

You could have a look at your water as well. If you don’t have the alkalinity to balance the dark roasted malts that can definitely lead to sharp or harsh tastes