Missing OG (High)

More vigorous boil than usual?

 

I doubt 12 minutes of mash would make much of a difference. What temp did you mash at? (not that this is going to give the answer, but I'm just curious).

And how accurate is your refractometer compared to a regular gravity meter? Did you check the OG with a regular gravity meter? Were the temperatures at testing time optimal?

 

I guess you lost about a half gallon that you weren't expecting? What was your post-boil volume?

 

when checking the pre-boil gravity, was your sample chilled?

 

I eyeball it these days, but a dowel or long metal spoon with marks on it is the way a lot of guys do it.

 

I filled a carboy with water which i measured out and made marks at the heights that correspond with the different fill levels

 

I'm brewing in a keggle with a graduated sight glass. I guess that makes it easier. You may consider etching some measurements on the inside of your pot?

 

This is the way to do it. Different buckets/carboys have different volumes, so the stick method has to be per that particular container.

Personally, I don't measure because I don't really care that much. It's usually close enough. But if this is important to you, then you need to measure.

Also, did you use the same type of hops? Leaf hops suck up wort. I doubt that's your issue here, due to the style probably not using a lot of hops, but it's worth a mention. I lost quite a bit of wort last weekend using leaf fuggles (4 oz).

 

“Combined with the fact that Wyeast 1469 is a BEAST, my 4.1% porter may now go as high as 5.4%, and will be a very dift. beer...”

I think somebody needs to RDWHAHB!

So, two details:

· At what temperature did you mash?
· What was your crystal/roasted grain bill?

It is entirely possible that you have a fair amount of unfermentable sugars in your wort. Even 1469 cannot ferment unfermentable sugars.

For your reading pleasure (from How to Brew):

“Dark caramel and roasted malts like Crystal 80, Crystal 120, Special B, Chocolate Malt, and Roast Barley have a high proportion of unfermentable sugars due to the high degree of caramelization (or charring). The total soluble extract (percent by weight) of these malts is close to that of base malt, but just because it's soluble does not mean it is fermentable. These sugars are only partially fermentable and contribute both a residual sweetness and higher FG to the finished beer. These types of sugars do not share dextrin's digestive problems and the added flavor and color make for a more interesting beer. The contribution of unfermentable sugars from enzymatic and caramel malts can be increased by mashing at a higher temperature (i.e. 158°F) where the beta amylase enzyme is deactivated. Without this enzyme, the alpha amylase can only produce large sugars (including dextrins) from the starches and the wort is not as fermentable. The result is a higher final gravity and more body.”

Cheers!

 

It seems to me there are two possibilities: either your gravity reading was incorrect, or you boiled off more wort than expected. My guess is that your initial reading might have been incorrect--I doubt you would have had that much more boil off than usual.

After some trials and tribulations, I came to the conclusion that the best way to measure preboil gravity was to cool the sample and use the hydrometer. (And of course be sure to stir up the wort before collecting!) It's not very hard to do, given that you're only cooling about 3/4 cup of fluid.

 

Well, for a mash temperature of 154°F you are about ‘in the middle’ wrt creating a fermentable wort. Mashing at 148°F would result in a very fermentable wort while mashing at 158°F would result in plenty of dextrins and a less fermentable wort.

“6.5% British Chocolate, 5.75% Crystal 120” A total of 12.25% of crystal/roasted malts (which is appropriate for a Porter) will provide lots of unfermentable sugars.

My guess is that between some dextrins from a mash at 154°F and the dark malt unfermentable sugars that your beer will have a fair amount of body (a not too low final gravity). Needless to say but 1469 will be the final judge on this matter. As the old saying goes: brewers make wort, yeast makes beer.

Please report back what final gravity you achieve with this batch.

Cheers!

 

I was suggesting this for kettle measurements.

 

did you take a gravity reading at the mash temp using a hydrometer? If so, then your mash gravity would be higher than you thought.

 

okay, then it does sound like a volume issue. Whether you had more in your kettle or less in your fermentors.

 

I measure my post boil volume with marks on the sides of my carboys. But if you can't measure your post post boil volume, you can compute it. Take (1 minus your preboil gravity), divide that by (1 minus your postboil gravity), then multiply by your preboil volume.

This assumes temperature corrected gravity readings.