Crystal vs Lactose for Sweetness

I'm interested in making a sweet stout. What would be the effect of using (say) 10-15% crystal malt for sweetness instead of lactose or oatmeal? I haven't seen any recipes which do that -- which tends to make me suspect it's not worth trying.

 

Lactose isn't really sweet in the sense that sugar is sweet. It is more full bodied, and slightly milky.

Crystal will be sweeter than lactose, but if you want a milk stout I'd go with the lactose. Lactose gives that creamy feel you want in a milk stout.

 

So a sweet stout make with (say) 15% crystal might be too sweet and too malty and not creamy enough compared to one made with lactose?

 

I find that they affect the end product very differently.

Lactose has a creamy sweetness to it, that isn't really quite "sweet". Think of the sweetness of milk or cream. It doesn't feel the same on the palate as a similar amount of maltose.

I find that you can have far more lactose remaining in the final product than unfermented maltose, before the beer starts to be too sweet. I haven't used lactose in years though, and I can't really comment upon exact percentages of it. But the mouthfeel of a beer with crystal in place of lactose will have a different mouthfeel.