Hello fellow brewers. !First Post Alert!
I have been brewing beer for 4-5 years, and last year I switched to all grain brewing. Early on, I used to have trouble controlling my OG. Some beers where too small, and some where too big. I figure this had a lot to do with my then constantly changing mashing methods. I since developed a way to adjust my pre-boil gravity to usually "peg" my target OG.
First I figure out my target OG in terms of total sugars. Say my target OG is 1.050 at a 5 gallon batch. Then my target gravity-points would be 50. (drop the "1.0") Then multiply by my length - 5 gallons. Giving me result of 250 pts*gals.
I know from dozens of mashes that I acheive about 30 pts*gals per lb of grain. So I divide the taget 250 pts*gals by 30 and I get 8.33 lbs of grain. I usually throw in about 1 extra lb of grain because I'll adjust my preboil volume DOWN to my target - and I get a healthy amount of extra wort to krausen/carbonate/starter with.
After the sparge/lauter, I mix my wort up in the kettle because I found that the first runnings (heavy SG) from the lauter sticks to the bottom of the brew kettle, and the low density late runnings stick towards the top, or simply put the wort is stratified. After mixing I take a temperature adjusted SG and volume reading. Lets say I end up with SG=1.040 and 7 gallons.
I then calculate the pts*gals of the pre-boil wort: 40 x 7= 280 pts*gals. My target is 250. so I adjust remove wort to compensate:
280 - 250 = 30 pts*gals - This is what I have to "remove" from the boil. Knowing that my wort is 1.040 sg (or 40 sg points) I know that I need to remove 30 pts*gals / 40 pts = .75 gals. I then remove this much wort - .75 gallons.
Now my pre-boil length is now 7 gals - .75 gals = 6.25 gals. I know from records that I'll loose just that much during a 60 minute boil. But if I need more pre-boil volume, I'll add some fresh water, to adjust. (most times I have to add a quart or two of water)
After my boil, I usually end up with a perfect target OG; in this example 1.050 or 50 pts.
I've never read or heard of this technique. It seems to work great. But I'm wondering if I'm strange for over-doing the target OG thing, to the detriment of my brew. I know my yeast bank pretty good, and I usually hit my ABV by .1 - .2 %.
Any questions, comments, concerns, laughter, or flames?