Extraction Efficiency

Can someone give a plain old rundown of extraction efficiency for AG? People are complaining of different efficiency levels but I do not follow what this is caused from and how it can be fixed? I'm just about to make the jump to AG and wanted to know more.

Thanks!

Here's a good article to start with:
http://byo.com/mrwizard/1145.html

Search on the forums to find lots of discussion regarding low or high efficiency and what causes it. There are many factors that effect it, some obvious, some obscure. The primary things most people find are lautertun design, grain crush, and pH of the mash.

Thanks for the reply, that site helped out.
I was reading a post earlier that said someone grinded their grain almost to flour for their mash (to raise their efficiency). How can you filter through this? I can see either the lines getting clogged during the sparge phase or just everything going out through the lines into the kettle.
Does the 'flour' bed become stiff enough for you to sparge? But wouldn't that mean that the sparge water would not drain?
How can you sparge effectively without getting either clogged lines or a kettle full of flour when grinding that small?

Also, by raising the pH of your mash...would that in turn raise your SG? If that were the case, someone could add a thicker additive (like honey) to their brew to raise their SG, but that would not mean that the efficiency would go up. It just seemed like the higher the SG, the higher the effieciency...but you could go around that by other means.

1. With crush there is a sweet spot where it's not too fine and not too coarse. This is very much system dependent. Even with a fine crush, you want to leave the barley's husks as intact as possible as this is what forms the filter bed, not the endosperm (flour). Grains that do not have husks such as rye and wheat often necessitate the addition of filter material (often rice hulls).

2. With pH there is also a sweet spot, usually around 5.3. It depends on which enzymes are active. See www.howtobrew.com for more discussion of this. Also note that almost all brewers will get 100% conversion of starch to sugar. The efficiency measurement is how effectively you get that converted sugar out of the lautertun and into the kettle.

3. There is no direct correlation between SG and efficiency by themselves. Efficiency is related to the SG and the grist you used for the recipe.

4. Adding additional fermentable material directly to the kettle (such as honey or sugar) has no effect on your lautering efficiency.

Thanks for the reply. I read that site a long time ago when I began extract brewing...so I think I skimmed over that part about AG brews. Now that information applies to me, so thanks!