Question on attenuation...

[Dillbag]

First off... Hello all!

This is my fourth (fifth if you count the first which didn't end up with much alcohol, but tastes great) batch, and it's my first "high gravity" brew...

I'm doing a Scotch Ale OG was 1.096... It's down to about 1.028 now 9 days later... which means an approximate attenuation of 70.8% The yeast is White Labs Edinburgh Scottish Ale which has an attenuation of 70-75%...

So, my question is two-fold... First, are they (White Labs) talking about the "true" attenuation or the approximate?

And second, what are the chances this will drop a bit more in SG? (obviously dependent on the first question...)

Thanks!

 

[zoebisch01]

Hello and welcome

First off, the attenuation cited is the normal range for the yeast. You can expect to see those numbers so your recipe should be based off of the cited attenuation. Under certain circumstances it is possible to push the attenuation higher. Proper oxygenation of the wort, proper pitch rate, proper temperature, no temperature shock and a few other factors can all influence the best case scenario.

Conversely, you can push the attenuation to the other end of the spectrum as well by not taking sufficient measures to attain the aforementioned conditions are met.

Another factor to consider is how much is truly fermentable in your wort. In AG brewing you can even alter your mash temperature to fine tune the attenuation indirectly.

In your case, you may be very close to your final gravity which is fairly good for a big beer like that. Without seeing the recipe we cannot say much more.


Edit: Sorry, yes they are talking about "apparent" attenuation.

 

[Dillbag]

Cool, thanks!

So, that's what I had figured was that WL would put the apparent attenuation... I'm kind of guessing that when everyone talks about it, it's almost always apparent because it's just too much work to calculate the actual...

So by the %attenuation that I've got, this batch is ready for a 2ndary... And I've realized that this is really my fifth batch as I'd forgotten about my lager which is lagering...

Here is the recipe for the BIG beer I'll take any comments on it:

Crystal 40L 5oz
Crystal 90L 5oz
Maris Otter 2oz
Peated Malt 2oz

Pale ME 2.9 qts
Amber ME 1 qts
Amber DME 1lb
Cane Sugar 0.25lb
Molasses 2 oz
KaroDark Syr 2 oz

BH: Kent Goldings 1oz
FH: Kent Goldings 0.5oz & irish moss

 

[zoebisch01]

Well from what I can see, you don't have overly much in the way of unfermentables. There is some in the Crystals, Molasses and Karo....and the Amber ME/DME will probably have some. The MO and Peat (I think the Peat as well) needs to be mashed to convert so you can't count on their contribution. So that will push your final gravity up a bit. The way to figure all this out would be to find out exactly how much fermentable wort you have and that is the number to use for your apparent attenuation calculations. Unfortunately there are a bunch of unknowns here, so I think the best approach is to secondary and let it sit for a month.

 

[Dillbag]

Yeah, that's kinda what I figured...

Trying to get a handle on a bit more of the science behind all this.

Is there a better book than Charlie P.'s for learning about the science of brewing?

I did do a partial mash with the grains (ie 1/2 hour at 160, and then rinse) so that should up my fermentables?

 

[zoebisch01]

Yeah, that's kinda what I figured...

Trying to get a handle on a bit more of the science behind all this.

Is there a better book than Charlie P.'s for learning about the science of brewing?

I did do a partial mash with the grains (ie 1/2 hour at 160, and then rinse) so that should up my fermentables?

If by better, you mean more scientific then www.howtobrew.com is a great place to start. Also browse the Wiki, lots of good stuff in there.

Yes the partial mash will convert the starches giving you more sugar.

 

[Dillbag]

Yeah, I meant more scientific... CP's book is great!

I'm interested in more of the nitty-gritty... Thanks for the links, I will be checking them out.

But if anyone does have book suggestions, those would be great too... I'd rather sit out on the deck and enjoy a HB while reading a book than sit inside and stare at a computer!

 

[david_42]

How to Brew is also available in a dead-tree version. Mr. Palmer has an engineer's approach to brewing. His utilization tables are superior to any of the formulas commonly used in brewing software and his Appendix on mash tun design will warm the heart of the most serious OCD case.