Liquid Malt Questions

[SCBeerDude]

I'm still an extract/mini mash brewer. I have seen and read a lot about "unfermentables" in liquid malts and the impact that they can have on brewing. I typically use the O'Shea's liquid malt, but just got some Briess from The Bruery and I plan to use that next. Though I am not quite ready to go all grain, I have noticed some high FG readings of late and wonder if a partial cause could be these "unfermentables" and/or poor quality liquid malt.

I'm addressing possible other causes of fermentation issues but, having set this up with all the above, wonder:

Are some liquid malt extracts better than others?
What are your experiences?
Preferences?

[brahn]

It's not so much that they're low quality extracts, but my experience says that typically the malt extracts do have more unfermentables than my all grain batches do. Yes, different malt extracts have different levels of fermentability. According to Palmer in How to Brew, Laaglander extract will typically yield about 50% apparent attenuation. The Midwest Supplies website lists the Briess extract as having about 79% fermentability. I believe O'Sheas sells Alexander extracts, Midwest sells them as well but does not list anything for fermentability.

Palmer discusses Gravity vs Fermentability here:

http://www.howtobrew.com/section1/chapter3-5.html