Ok so I have new 10 gallon kettle and want to do a BIAB
Years ago I AG then last few years kits. Now going to try BIAB.
So some quick questions
10 gallon pot how big a batch 5 gallons ???
What is the highest OG I can shoot for with a 5 gallon batch?
Any suggestions for my first recipe?
How quickly is saccrification complete and why such a long mash?
I am sure all of this has been asked thousand times so I apologize for nobbiness of my nooberocity
About the largest full volume mash you could do would use 15 lbs of grain and 8.08 gal of strike water. This would have a mash volume of about 9.5 gal. These values come from this calculator:
http://pricelessbrewing.github.io/BiabCalc/. The 15 lbs of grain would have a sugar potential of:
15 lbs * 37 pts/lb = 555 potential points
If we could extract all that potential sugar into 8 gal of wort we would have a specific gravity of:
1 + 555 / (8 *1000) = 1.069
This converts to 16.9°Plato, which means our 8 gal of wort would be 16.9 weight% sugar. So the total weight of the sugar would be:
0.169 * 1.069 * 8.329 lb/gal * 8 gal = 12.05 lbs
Since we mashed with 8.08 gal of water, the total weight of the wort in the mash (at 100% conversion efficiency) would be
8.08 gal * 8.329 lb/gal + 12.05 lbs = 79.35 lbs
And, the wort would be
12.05 lbs sugar / 79.35 lbs wort = 0.152 => 15.2% sugar
So our wort in the mash best case would be 15.2°Plato or 1.062 SG. If we have a pre-boil volume of 7.18 gal (from Priceless calcuator) @ 212°F, we would have 7.18 * 0.96 = 6.89 gal at room temp. So our gravity points in the boil kettle would be
6.89 * 1000 * (1.062 -1) = 427 points
And our mash efficiency would be
427 points / 555 points = 0.77 => 77%
The 6.89 gal of pre-boil wort would boil down to about 5.69 gal, and have an OG of
427 points / 5.69 = 75.1 pts/gal => 1.075 SG
With about 0.19 gal trub loss, you would net 5.5 gal in the fermenter.
So, the highest OG you could target for a no sparge 5.5 gal (to fermenter) batch would be about 1.075. You might be able to get slightly higher efficiency and OG by squeezing your bag more aggressively to reduce the retained wort (and sugar). You could do higher gravity brews using more than 15 lbs of grain by using less strike water, and sparging to get your pre-boil volume.
Time to complete saccharification depends on a number of variables. The primary variables are: crush size, temperature, mash thickness, and pH. To get good conversion rates you want your (room temp) mash pH to be in the range 5.3 to 5.7. To complete a mash in 30 minutes at about 154°F, you need to have a crush like coarse flour or corn meal, and a mash thickness of around 2 qts/lb or higher. A mash with a crush from a 0.040" gap mill, and 1.25 qt/lb mash thickness might take and hour or longer. A mash at 148°F vs. 154°F might take 25% - 50% longer to complete. You need to monitor you mash either with SG measurements or an iodine test to determine when your mash is complete under your process conditions.
Hope this isn't a case of TMI too soon, and is helpful to you.
I support others who recommend a recipe with a simple grain bill and hop schedule for you first time thru the process. There will be plenty to keep you busy just from the process side.
Brew on