Any source for predicting FG based on Grist?

[chaglund]

So aside from doing a forced ferment test on a batch, is there any good source that discusses the relative impact darker specialty grains (containing unfermentable sugars) has on the FG?

Understood that mash temp has a potentially greater impact, and that malts will vary by maltster, but clearly there is some calculation in brewing software that predicts this. Do darker caramel malts have more unfermentable sugar than lighter caramel malts? Where do roasted grains stand?

Trying to formulate a dubbel with particular attention to FG. Want it to be fully attenuated, but have a good malty body behind it.

[tom_sawyer]

I don’t think theres a significantly higher proportion of unfermentables in darker malts. By example, a dry Irish stout is about as black as it gets and is, as the name implies, dry. The key is the mash temp, for an attenuative wort you want a lower mash temp. Or you can mash higher and add candi sugar syrup to the kettle, those will have some unfermentables. Maybe use a little dextrin/carapils malt for body.

I think a good dubbel is packed with complex flavors from both malt and yeast and even though its fairly dry that is what gives you a sense of body.

[shadetree]

Brewing software isn’t calculating an FG based on the grist, it’s using the yeast manufacturer’s attenuation number which is just a ballpark at best.