Mashing Efficiency

[joecast]

so whats this all about?? i sort of get the idea that you only get so much fermentable out of the mash, but is there any way to tell what your efficiency is going to be?
i havent mashed yet and after checking out the different results between 60% and 70% efficiency using promash, there seem to be quite a variation in OG. is there a generally accepted number that you guys use, or do you have an idea of what you get just based on past experience? thanks
joe

 

[Justin]

Have a look at John Palmer's How to Brew online book. www.howtobrew.com

Off memory there is a section on how to calculate this. What you need to find out is a few specs on the grain you use, I have some of these that I can give you but I haven't yet collated all the info on my grains. But basically you can work out the efficiency of your system by working out the maximum possible amount of sugar that can be extracted and the actual amount you did extract. Hmm, bit confusing to try and explain here, ok, I just copied some stuff off a site below. Hope it helps.

Extraction rate
Calculating your extraction rate or mash efficiency/yield is useful for determining the efficiency of your system, and to determine your expected OG. The following formula gives the potential SG if the efficiency of your setup were 100%:
Malt SG * 8.333 * m
SG(pot) = -----------------------
V

Where Malt SG = extraction points/pound/gallon as specified with the malt
m = mass of malt in kg
V = volume of wort in liters

After collecting the sweet wort into your brewpot, take an SG reading, and compare this to the SG(pot) to calculate the efficiency of your setup:

SG(measured)
Setup efficiency = ----------------
SG(pot)

In the future you can use this result to calculate your expected OG, by multiplying the potential SG and the system's efficiency:

SG(expected) = SG(pot) * Setup efficiency

Just remember that in order to calculate the OG, the volume V must be the after-boil volume, because of evaporation during the boil.

Bit confusing I know. But I think the Maltcraft website has the malt specs you need.

Hope anyone else can help you out too.

JD

 

[Murray]

Jayse is the brew maths man, he will fill you in on the metric info.

From my fiddling around I have SG(points)=386.5*Wg*Y*Y'/V
Wg = grain weight in kilograms
Y = Malt extract efficiency (from the supplier)
Y' = Mash efficiency
V = brew volume
SG(points) = Specific gravity in points (final two numbers)

I assume my mash efficiency to be a constant regardless of grain, so I work out the total expected SG for all grains together as...

SG(points)=386.5*Y'*(sum of Wg*Y)/V

To work out your efficiency, measure your SG and use the above equation as written below.

Y'=SGpoints*V/386.5*(sum of Wg*Y)

It works for my system, anyway. Jayse can tell you for sure.

 

[Wreck]

Are there some simple things to do to improve your mash efficiency?

I've only done a couple of mashes so far, and I think I've been getting around 55%.

 

[Batz]

Takes a bit of getting your head around it at first joecast ,
I was passed this site helped me

http://hbd.org/uchima/tech/efficiency.html

Hope it helps
Cheers Batz

 

[Justin]

Grain crush. And your sparge. Get these to optimum and your efficency will improve. There is some debate about fly sparging and batch sparging. I only have limited experience and have only ever fly sparged.

My efficiency was pretty good.

I have a Barely Crusher grain mill on it's way to my house via the long way around the world. Hooray. Adjustable roller mill. Should get a good crush out of it. Hooray again, I'm getting a mill.

JD

 

[Murray]

With my cheap setup, batch sparging is my only option, however I regularly get around 80% efficiency. A good crush is important, IMHO you should crush as finely as your system allows before it sticks.

 

[crackers]

murrays right on the mark with both counts
1 jayse is the man to speak to (helped me out alot)
2 the metric formula is more accurate with the maltsters extract % for each different malt.

i started on the points / pound / gallon mathmatics
but ive just started to work out recipe formulas using the metric system.

cheers
crackers

 

[jayse]

jeez my high school maths teachers would laugh at at that.
'Jayse, a maths wiz' hahaha.

anyway brew maths is quite simple.

How it works is all malts and adjuncts etc give a different gravity.
The specs are all written as H.W.E which is hot water extract with sugar being the highest at 386 so everything else is given as a % of that. ie, pale malt is around 81% which gives you around 309. this is the total gravity you can get with 1 kilo in 1 litre but it is impossible to get this, this is 100% effeincy.
the same goes for american calcs but its in P.P.G which is the gravity of 1 pound in 1 gallon. The same specs are used ie. 81% for pale malt gives you 37 points of gravity.

So a simple example to work out total potential for 5 kg of pale malt in 23 litres is
5 x 309 / 23 = 67 (1.067)

now to work out your effiency you divid the gravity you got with this brew. Say you got 1.050 so 50/67 =.74 you got 74% effiency.
Then next time when you do the calc. 5 x 309 /23 =you simply times this by .74 .
This gives you your expected gravity,

For you first batchs i would stick to using 60-65%.
So do the 5 x 309/ 23 = 67.
then times 67 by .65 = 43(1.043)


am i making any sense here
Jayse

p.s the hwe numbers are all on the malt craft site other malts like crystal malt are around 75% some malts can be lower and some higher.
to get the number times 386 by the percent as a decimal point ie pale malt at 81% gives you 386 x .81 =312

 

[Stratis]

so whats this all about?? i sort of get the idea that you only get so much fermentable out of the mash, but is there any way to tell what your efficiency is going to be?
i havent mashed yet and after checking out the different results between 60% and 70% efficiency using promash, there seem to be quite a variation in OG. is there a generally accepted number that you guys use, or do you have an idea of what you get just based on past experience? thanks
joe

A good start is to assume around 65% for your first mash. Whether or not you get this doesn't matter. I take a hydrometer reading after mashing (and adjust for temperature). If I get lower/higher efficiency than expected then I can boil down or dilute as required.

I use http://hbd.org/cgi-bin/recipator/recipator for all my calculations. It will tell you what the specific gravity after mashing should be given a certain efficiency.

 

[joecast]

wow! thanks for all the replies. ill have to wait till after my first batch for a "definite" figure but that helps a lot.

so the main things we, as the brewers, can do to affect the efficiency of our mash is to use just enough sparge water (but not too much), and crush the grains evenly and fine (but not too fine). ok, ill have to write this down. oh, and get a calculator.
joe

 

[Justin]

Evaluation version of Promash too, Joe. If you can. It has a lovely little function that allows you to work out your gravity while correcting for temperature. ie. because most hydrometers are calibrated at 20 or 21oC and if you take your reading at 50oC your gravity is way out. If promash is handy then chuck in your gravity and temp and out comes the corrected gravity. Beats cooling down you wort sample for a grav reading.

 

[joecast]

A good start is to assume around 65% for your first mash. Whether or not you get this doesn't matter. I take a hydrometer reading after mashing (and adjust for temperature). If I get lower/higher efficiency than expected then I can boil down or dilute as required.

thanks stratis, thats a good point. its not so important that my brew is 20l or 23l. im not worried if it comes out a bit less if i can get closer to my taget OG
joe

justin,
thats what got my to ask in the first place. i was adjusting the efficiency and saw how much it changed the OG!! not as worried about it now that i know i can work around it.

 

[jayse]

yeap boiling down or diluting is a good option.
if your doing a very hoppy brew with lots of hops on the end like 'skunk fart pale ale' then boil down untill your very close to the gravity before you had the last additions of hops.
but with a stout or something you can easily just keep boiling till your at the right gravity with out affecting the hop balance very much.
I did this yesterday with my stout and F.W.H only wheat beer.
Mearuring the gravity of the boil is a very very good idea.


cheers, all brewed out Jayse.