I'm still a bit confused on this so forgive my ignorance.
When it comes between conversion and lauter efficiency, would they be the same thing you just pulled your bag from the single kettle and did NO squeeze? I'm wondering if conversion would be calculated before the bag is moved, and lauter is everything after that (squeeze and sparge).
eGrain still confuses me. From what you've said, it sounds like a constant 36.9. It also sounds similar to what I'm doing to calculate the max PPG. I take the potential SG of each grain type (per Beersmith) and then multiple that by the pounds of grain to get the max points. That value is divided by the full volume in gallons to get the max PPG. I use that max PPG as the baseline - if I were to get 100% of all the possible sugars then that would be used to get the gravity.
In the homebrew world, mashing is considered as the process of turning malted grain into wort in a kettle. There are two steps to this process:
- Converting the starch in the grain into sugars (saccharification), and
- Separating the created sugar from the spent grain (lautering)
We define the efficiency of the combined steps as mash efficiency, and more formally as:
Mash Efficiency = Weight of Sugar in BK / Weight of Max Potential Sugar in Grain
We can also define efficiencies for the two steps of the overall process (i.e. conversion efficiency and lauter efficiency):
Conversion Efficiency = Weight of Sugar Created in Mash / Weight of Max Potential Sugar in Grain
Lauter Efficiency = Weight of Sugar in BK / Weight of Sugar Created in Mash
So conversion efficiency can be determined before the the wort and grain are separated. Conversion efficiency only measures how much of the available starch was converted to sugar. Lauter efficiency only measures how well you separated the sugar from the spent grain (not affected by how much sugar you created.) Some simple algebra shows that:
Mash Efficiency = Conversion Efficiency * Lauter Efficiency
When diagnosing low mash efficiency, it's important to know whether your conversion efficiency is low, or your lauter efficiency is low, since the actions required to fix each of those are totally different.
Let's look at an example. Suppose we have 10 lbs of grain with an average extract potential of 80% (or 46.17 * 80% = 36.9 pts/lb.) That means if we convert all of the starch to sugar (100% conversion efficiency) we will have 10 lbs * 80% = 8 lbs of sugar dissolved in the wort in the mash. On the other hand if we only get 85% conversion efficiency, the we only have 10 lbs * 80% * 85% = 6.8 lb of sugar in the mash.
Now let's say we have a lauter process that gets 80% of the created sugar from the mash to the BK. If we've done things correctly, then the wort concentration will be uniform throughout the mash, so 80% of the sugar weight will correspond to 80% of the wort volume. So getting 80% of the sugar out of the mash is the same as getting 80% of the wort out of the mash. In the case of 100% conversion efficiency, the total collected sugar will be 8 lbs * 80% = 6.4 lbs of sugar in the BK. The mash efficiency is then 6.4 lb / 8.0 lb = 80%. In the case of 85% conversion efficiency with 80% lauter efficiency, the total collected sugar will be 6.8 lbs * 80% = 5.44 lbs. The mash efficiency is then 5.44 lb / 8.0 lb = 68%.
If we squeeze more wort out of the spent grain, we get more sugar as well, so the lauter efficiency (and the mash efficiency) go up.
That's a long winded answer to say: yes conversion efficiency is before you pull the bag, and lauter efficiency is what percentage of the sugar created before you pulled the bag is in the collected wort in the BK after you pull the bag and squeeze, sparge, or whatever.
eGrain is just the name of a variable that Braukaiser invented to use in his equations. It is really just the extract potential of the grain in weight percent. So, if the potential of the grain is 80% then that means that 10 lbs of grain can produce a maximum of 8 lbs of sugar. The only constant is the pts/lb for sucrose, which is 46.17 pts/lb. If you put in 1 lb of sugar, you will get 46.17 gravity points. To determine pts/lb for other grains/adjuncts you multiply the potential in wt% times 46.17. Potential in wt% is what is usually reported on malt analysis sheets. Most brewing software converts the potential in wt% into pts/lb in order to make things easier for users.
If you total up pts/lb times lbs for each malt you use and divide by the volume of the wort in the mash, you get the maximum possible SG of the wort in the mash at 100% conversion efficiency. (Max SG ~= 1 + [pts/lb * lbs] / 1000.) The problem is that wort volume
does not equal strike water volume. This is because the sugar dissolved in the wort increases the volume. Dividing total pts by strike water volume yields a useless number. It will give you an apparent SG that is higher than actually possible. If you then use that SG to determine conversion efficiency, you will get something lower than your real efficiency.
Brew on