Overshot my OG

I way overshot my OG on my first all grain batch, so I reviewed my brew day notes to see where I went wrong. I see now that I kept sparging until I had enough wort in the kettle to make my pre-boil volume, whereas I should have stopped sparging and used top off water instead.

This got me thinking of a method to keep this from happening again. I came up with the following:

1. Calculate the gravity points based on the original recipe i.e 5.5 gals. x 1.055 OG = 302.5 gravity points.

2. Mash/sparge and calculate gravity points collected i.e. 4 gals x 1.080 OG = 320 gravity points.

3. If Step 2 is higher than Step 1, remove enough wort from the kettle to end up with the correct amount of gravity points, and make up your volume with top off water. If Step 1 is higher than Step 2, keep sparging and repeat Step 3 again until you have enough gravity points. If you end up with a greater pre-boil volume in your kettle than you need, just boil it down before you start your hop additions.

Will this method work while I dial in my system?

Well what you should do is figure out your mashing efficiency. You obviously started with a set amount of grain to get a specific pre-boil vol, right? This is your mash efficiency.

Then you boil, cool, and transfer to your fermenter. Any losses here make up your brewhouse efficiency (such as wort left behind in the brew kettle).

Mash efficiency IMO is the more important one to figure out first. That way you can know how much grain you need to get your pre-boil gravity.

So what efficiency did you assume when you started making your recipe? 60%, 70%, 75%, 80%? You got a better efficiency than that. So next time you just have to use less base malt to get your OG (because your efficiency is greater that what you originally assumed).

I guess you can top-off with water to dilute your pre-boil gravity or add malt extract to boost your pre-boil gravity. But you want to be able to hit your numbers dead on every time with the grain bill.

I didn't make any estimate of my efficiency before I started. I had what I felt were pretty good estimates for grain absorption and evaporation so I could "guesstimate" the pre-boil volume that I needed.

I was brewing a scaled down version of Jamil's Brown Porter with a grain bill reduced to what I could mash in my 5 gallon MLT. It seems to me that using the steps I listed above that knowing efficiency isn't important - as long as its "close" to whatever was assumed by the original brewer you can either sparge a little more or use top off water.

Wouldn't it be nice if it worked like that?

Every recipe posted has an assumed mash efficiency, sometimes its 70%, sometimes its 60%. It can be whatever the brew that made the recipe got.

You need to use X lbs of grain to get the OG that you want. That is your mash eff. & that is what you must figure out. Or else you will be doing what you are talking about which is shooting in the dark. Its only going to make things more difficult.

Use recipes more as a list of ingredients, not a detailed step-by-step instruction booklet.
The % of malts is more important than the amount of malt listed in the recipe.

Also: since you already brewed you can calc. your efficiency from your last brew and use that as your starting point for your next one. I use Promash to do this. Someone else can chime in if they know of an internet-based eff. calculator.

Or you can post your grain bill and pre-boil and post-boil volumes and I can tell you what your eff. was.

Your better off knowing the efficiency of your brew setup. It may take a few brews before you really know. Then you can ajust your base grains to reach this each time you brew. Having good efficiency saves money. In my opinion that's why homebrewing craft beer is cost sufficient. My system is 80% and I'm very proud of that since I batch sparge.