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Mash temps and calculations

B

brewmaster808

Is there a way to make the estimated OG and FG change values when selecting different mashing temps / styles? Thank you.
 
I would love to do this, but unfortunately there is a lack of empirical data (that I am aware of) to tell me how much to change the FG/OG for a given mash temperature.

Everyone knows that a higher mash temp will result in more unfermentables and a higher FG, but I have not been able to find a good reference where anyone can say by how much.

This leaves a bit of a dilemma since I have tried hard to make sure that the program is properly backed up with hard data.

Cheers!
Brad
 
Brad is right, and I too would truely like this side of brewing to be a science rather than an art.  I recently brewed a Wee Heavy (Kilt Lifter - see the recipe archive) that BeerSmith predicted to be 1.133/1.035,  well I nailed the 1.133 (thanks Brad) but with that big of a beer the 1.035 was suspect.  A 1.045 or 1.050 would be more likely.  I wanted to hot something in the upper 20's about a 1.027-1.028.  I performed a step mash via a decoction and hit 1.019.  I never thought I'd get this big a beer under 1.020. A great beer but in hindsight an imperial 80/- rather than a Wee Heavy,  that is a 15+% 80/- beer.  Great taste.

Point is that it is hard to estimate a FG.

Fred
 
Brad, do understand what you mean about a good reference. I to have looked and looked and not found. I searched the net and many pubs for this answer and found nothing to. Just thought you might of had better references so thught I would ask. Just seems like some pro brewers that brew a lot of the same type beers and played with temps would list some data on it. Maybe with this post get lucky and someone will give a referance. And by the way I been very happy with Beersmith.
 
Thanks!
 I will certainly print this out and take a look at it to see if it is something I can generalize in some way.

Cheers!
Brad
 
Brad could you look this formula over and tell me if it is correct. Just assume that there are no varibles. I think if it works I might have the rest figured out.

If I had two batches of wort both with a OG of 1.050. The differrences being one has a 76% fermable sugars and the other has 65% fermable sugars. If I use an yeast with a 70% attenuation

Temp at 60C
(100%-70%=30%). So then FG=1.050 * 0.30 = 1.015 (fermable sugars, 100% - 76% = 24%) .24 * 15 = 3.6 then 1.015 + .0036 = 1.018 expected FG

Temp at 68C
(100%-70%=30%). So then FG=1.050 * 0.30 = 1.015 (fermable sugars, 100% - 65% = 35%) .35 * 15 = 5.25 then 1.015 + .00525 = 1.020
 
Not quite...
 The yeast makers use apparent attenuation for their products defined as:

 Appt_attenuation = (OG-FG)/OG * 100

Note that the OG and FG are in points ((drop the 1.00 part and multiply by 1000 -- for example 1.056 = 56 points.))

or rewritten to calculate FG:

 FG = OG -  (Appt_attenuation/100) * OG

Note that the percent fermentables does not appear - the calculation is the overall "apparent" attenuation unadjusted for percent of sugars fermented.

This is basically what BeerSmith does to calculate FG.

Cheers!
Brad
 
Deleted this message, have recieved email from White labs and confirmed there formula is same as Wyeast just done in another fashion, the -1 was meant as -1.0 and not as subtracting 1 point. My mistake. Here is the reply from White labs.
That is just the formula simplified, your probably doing it automatically by not using the 1 in your formula, for example instead of 1.060-1.010, your doing 60-10/60.  But you can see how 1.060-1.010/1.060 won't work.
 
Good,
 I was working last night to show that the two formulas were the same, but ran out of time and was pulled onto another project...so I'm glad to hear that they are indeed the same.

Happy brewing (as always)!

Brad
 
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