Brewday discrepancies

[bigdave]

The last 2 brewdays I've reached a 71% mash efficiency (which is about what I'd expected & calculated for) & have collected the correct amount into the FV but the OG has been substantially out but I'm not sure why?..

I use the pre-boil SG and beer engine to calculate mash efficiency & I allow about 4ltrs dead space and hop loss.

Anyone able to offer any help on this one?

[Rick_UK]

Most likely a dodgy reading or measurement.

[bigdave]

Right, so... I've been looking back over my numbers...

Beer Engine states that I'm getting a 70-71% mash efficiency based on a reading of 1.068 @ 20ºc.. To get my post boil gravity of 1.080 @ 20ºc, evaporation would have to be 18% and not the 10% that I'd calculated (4.5ltrs lost to evaporation rather than 2.5ltrs).

This makes sense because when I was having hop stopper issues earlier in the year, I entered a 4ltr loss into beer engine as it seemed to make the final volume turn out right. In actual fact on the last 2 brews it's been much closer to 1.5-2ltrs. Supporting the theory that my Evaporation is 18%.

So, the question is... If I have an accurate figure for my losses, evaporation rate and mash efficiency based on pre-boil SG readings, why is beer engine giving me an estimated OG which would require an 80-85% mash efficiency?

[Matt12398]

Are you measuring you pre-boil volume. Without that the efficiency values you're getting that are fairly meaningless surely?

[bigdave]

Yep. Both brews I've measured volume and gravity pre boil.

[bigdave]

I'm wondering if running BE on a mac has caused some database confusion, giving me false readings?.. I'm going to try out BeerSmith's 21day trial with identical recipes to see if it gives the same estimations.

[vacant]

evaporation would have to be 18% and not the 10% that I'd calculated (4.5ltrs lost to evaporation rather than 2.5ltrs).

Evaporation is not proportional to brew length.

Think about it: if you boil a kettle for an hour it will probably boil dry (100% loss of 1.5 litres), but there comes a point where the same kettle element won't be able to boil (150 litres? 300 litres?) due to heat loss caused by the increasing surface area of the wort against the boiler and air: 0% loss. So evaporation rate decreases with increasing brew length.

I use 4 litres/hour for one element, my brew lengths vary from 20 to 40 litres. Obviously it boils off slightly more than 4 litres for a 20L brew, slightly less for 40L. Expecting to boil off 2L (10%) in a hour for a 20L brew but 4L (10%) in a hour for a 40L brew with a fixed output element makes no sense.

If you can regulate your heat and achieve the same vigour of boil (turbulence at the surface), then your boil off will be will be static - e.g. 4 litres/hour regardless.

[Ben711200]

evaporation would have to be 18% and not the 10% that I'd calculated (4.5ltrs lost to evaporation rather than 2.5ltrs).

Evaporation is not proportional to brew length.

Think about it: if you boil a kettle for an hour it will probably boil dry (100% loss of 1.5 litres), but there comes a point where the same kettle element won't be able to boil (150 litres? 300 litres?) due to heat loss caused by the increasing surface area of the wort against the boiler and air: 0% loss. So evaporation rate decreases with increasing brew length.

I use 4 litres/hour for one element, my brew lengths vary from 20 to 40 litres. Obviously it boils off slightly more than 4 litres for a 20L brew, slightly less for 40L. Expecting to boil off 2L (10%) in a hour for a 20L brew but 4L (10%) in a hour for a 40L brew with a fixed output element makes no sense.

If you can regulate your heat and achieve the same vigour of boil (turbulence at the surface), then your boil off will be will be static - e.g. 4 litres/hour regardless.

I was under the same impression, having learnt grain brewing through BIAB and using the spreadsheets on BIABrewer. These work out estimated evaporation as a litres/hour figure using the diameter of your boiler to calculate.

[bigdave]

This makes sense. Having used Beer Engine almost exclusively it's something which I've overlooked as BE bases evaporation calculations on an %. Having setup my own equipment in BeerSmith it has calculated a 'boil off' of 4.45 ltr/hr, which is accurate on the % of the volume on these 2 brews. So completely forgetting about evaporation as a % I think a change is software might be all I need to improve my brewing accuracy.

I'm going to sit down this evening and finish customising beersmith to suit my setup then enter the last 2 brews to check and compare against Beer Engine.

[PhilB]

Hi Dave

If you're getting the right volume into your FV, then I'd suggest you've got Beer Engine calibrated (in terms of losses) for your setup allright ... it's just the efficiency figure that you need to sort out (I know, that's easy for me to say ) ... with respect, are you sure you're using the efficiency calculator in Beer Engine correctly, there are actually two different efficiency calculators in the tool (switched by choosing the appropriate radio buttons) which calculate two different measures for efficiency, using different algorithms ... in particular, the differences are exaggerated if there are any simple sugars ("copper sugars or syrups") in your recipe. Were there any of those in your recipe?

From the BE Help info ...

If overall efficiency is selected, then measure the volume and gravity of the wort in the fermenter, before (or very soon after) the yeast is added, and put the figures in the appropriate boxes. If mash efficiency is selected, then measure the volume and original gravity of the sweet wort collected from the mash tun (including spargings). This can be the sweet wort collected in the copper, but before any copper sugars or syrups are added.

It is important to appreciate the distinction between 'overall efficiency' and 'mash efficiency', because the point at which volume and gravity is measured is different. The appropriate radio button must be selected and the parameters measured at the proper point and entered into the boxes. The difference between the mash efficiency and overall efficiency radio buttons is that copper sugars and syrups are excluded from the internal calculation when mash efficiency is selected, but are included when overall efficiency is selected. It matters not if any dilution liquor has been added to either the copper or the fermenter prior to taking the readings.

Cheers, PhilB

[DeGarre]

bigdave, why don't you post your figures and we can break it down?

ME% : amounts of various malts, preboil gravity, preboil volume.

Efficiency into the FV: postboil gravity, volume into the FV.

If you post the figures someone will see what's up.

[bigdave]

Hi Dave

If you're getting the right volume into your FV, then I'd suggest you've got Beer Engine calibrated (in terms of losses) for your setup allright ... it's just the efficiency figure that you need to sort out (I know, that's easy for me to say ) ... with respect, are you sure you're using the efficiency calculator in Beer Engine correctly, there are actually two different efficiency calculators in the tool (switched by choosing the appropriate radio buttons) which calculate two different measures for efficiency, using different algorithms ... in particular, the differences are exaggerated if there are any simple sugars ("copper sugars or syrups") in your recipe. Were there any of those in your recipe?

Cheers, PhilB

Efficiency was/is deffo set to mash efficiency with no simple sugars added.

bigdave, why don't you post your figures and we can break it down?

ME% : amounts of various malts, preboil gravity, preboil volume.

Efficiency into the FV: postboil gravity, volume into the FV.

If you post the figures someone will see what's up.

I write everything down as I'm brewing so will get the recipes and all the bumf posted up when I get home.

[bigdave]

Here's the most recent brew as calculated in beer engine:



Before brewing I check my numbers working backwards, so to get the right amount in the FV (in this case 17ltrs)

17 + 4 (loss) =21 + 300ml(hops) = 21.3 + 10%(evaporation) = 23.5ltrs in the boiler pre boil (rounded up)
23.5 + 7.4(grain loss) = 30.9ltr total liquor. Rounded up to 31 for ease.

So..

Strike at 72.7 degrees = 65 degree mash (I've intentionally mashed low as BE has predicted such high final gravity that mashing at 68 would leave it sweet.)

15ltr mash topped up with 5ltr @85degrees - collect 12.6ltrs in bucket with measures on then added to boiler
Batch sparge 11ltrs - collect 11ltrs in same bucket as above and added to bucket
Total pre boil - 23.6ltrs

circulate 5-10ltrs in boiler then take sample for mash efficiency reading. Boiler on

Pre boil 1.060 @ 44.8 = 1.068 @ 20 = 68% mash efficiency in beer engine.

Boil completed,

Chilled to 42degrees in 15mins

Left to stand for 30min then drained to FV.

Sample for post boil gravity taken at about 1/3 drained (makes for a clearer sample) reading

Post boil 1.074 @ 40 = 1.080 @ 20.



Interesting thing is, if this beer finishes as 1.012 it will be the correct abv

[DeGarre]

OK, thanks, just to kick things off.

7.395kg grain at 305 degL
23.5L volume at 1.068 is 73% ME

17L volume at 1.080 is 60% efficiency
17L volume at 1.091 is 69% efficiency (which is close to 70% on the table)

what i don't understand is it 1080 or 1091 going into FV?

pls note my 305 figure is based on the extract numbers from my grains, not what you have in your system.

[DeGarre]

So when beer engine says mash efficiency it is actually the efficiency for 17L ie what goes into the FV. But still can't understand what is 1080 gravity...