Originally Posted by mgortel
My guess is that mixing the 20 and 40 equally to approximate the 30 would be better than choosing all 20 or 40.....
Either way I cannot imagine it making a real noticable difference.....
They are similar enough as to not be a huge difference, although an expert could probably pick up the differences, as the 20L is more caramelly sweet while the 40L is still sweet but not as candy-like.
A great way to make a good American amber is to "layer" the crystal malts for depth of flavor. Say, .75 pound of 20L and .75 pound of 80L. It doesn't taste like 1.5 pounds of 60L, though- it's got some caramel sweetness, some toffee notes, and some depth to it, while 1.5 pounds of 60L might be lacking the toffee notes and the caramel and give a different crystal malt flavor.
I would not give a though to subbing 40L for 30L, but I would think more about bigger changes in a recipe depending on what I was hoping to get in the way of flavor.