Low Mash Effiency

[WM7793]

I was wondering whether anybody could throw some light on why my efficiency is so low. I am only making small batches until comfortable with Beersmith and actually making the beer.

The first couple of all grain brews were a matter of trying to make sense of the process which now I think I have a handle on.

I have put the numbers back into Beersmith and it is saying that I have a shocking 49.6% !!

I have a 33L Colemans coolbox and followed the proceedure for mashing, temperatures, and volumes for batch sparging to the letter. The equipment profile was set up for an estimated efficiency of 66%.

I hit my mash temperature of 66 degrees C and left it there for 90 minutes. After 90 minutes it had dropped to 62.6 degrees C

First volume was 10L, SG 1040
Second volume was 10.8 SG was 1.000

Beersmith estimated pre boil SG was 1.026 compared to 1.020
Measured volume prior to boil 20.8L, SG 1.020

Post boil volume was 13L (spot on from Beesmith)
Post boil SG was 1.040
Estimated SG was 1.043

Now as far as I can remember, I have everything by the book. No dough balls etc etc.

Can somebody please help me here?

Best regards,
WM7793

 

[pittsy]

What is your grain bill ? you should mash in with around 2.5 litres to 1 kg of grain , this will improve efficiency a little . Insulate your coolbox lid , they are designed for staying cool not warm so lids are empty (get expanding foam in it , drill a hole and fill) This will help you maintain a more stable temp . If you want get some iodine and test a little bit of the mash , if it goes dark black/blue there is still starch left to be converted (mash not finished) if it remains orange/red then mash is finished .
It sounds like you are batch sparging (i do too ) after emptying first water from tun and refill with sparge water give the mash a good stir , if you can do this twice instead of once (use less water so you can do it twice) it will help drain out missed sugars .
Are you sure on the temp of the mash , is your thermometer checked . You could be mashing in higher than you thought and getting less fermentables ( though that would mean a higher finished gravity reading more than a low SG reading ) .
What grains you using , some are better than others for efficiency .

 

[WM7793]

Thanks Pittsy for your reply.

Grain bill was 2915g (only 13L batch).
The mash is ratio is 2.78Kg/Litre

In order to reduce the deadspace between the grain and the coolbox lid, I made an rectangular foam block covered in tinfoil and hoped that this would retain the heat. Although your idea of drilling holes and fill with expanding foam would obviously help a great deal too.

Now looking back over the data, I feel that I have made a basic mistake in the numbers, please correct me if I am wrong here.

When taking the measured pre boil SG, ie 1.020 it was at 64 degrees C against the predicted SG ie 1026.

Now, when this is corrected for temperature at 20 degrees C it comes out around 1.035, (against a predicted 1.026) which when put back into the Beersmith gives me a measured mash efficiency of 87%, rather than the 49.6% based on the input of 1.020.

Does Beersmith allow for the higher temperatures at pre boil? or does the value that you enter for pre boil SG, have to be a cooled sample at 20 degrees C?

Either way, the numbers do not tally. I would appreciate your thoughts.

Best regards,
WM7793

 

[Duxuk]

I made your efficiency 60.47% using 295 as the "magic number" representing a typical ale grain bill. 59.46% if you used just maris otter. As mentioned you might like to better insulate your mash tun. Did you measure the SG of your sparge runnings? Was your sparge water at the right temperature?
On the bright side 1040 isn't such a bad OG. The beer will probably be a cracker :

 

[pittsy]

Beersmith usually gives reading for corrected temp , yours may be set at 20c or 15c , it should say on the side of hydrometer so anyway you need to cool sample to get correct reading . btw if your finished volume was 13 litres and you got 1040 then i make that 58% efficiency , with practise and care you should be able to get better , maybe 70% plus and water treatment also usually results in better efficiency (as well as better beer) .

 

[WM7793]

Thanks guys for your replies, really appreciated.

Could you please let me know what formula you are using to calculate the efficiency, so that I can do additional calculations on further brews and cross check with Beersmith?

Best regards,
WM7793

 

[pittsy]

i used beersmith and with my equipment settings etc , added your total volume and used pilsner malt as 2900g and kept lowering efficiency until i got 1040 which was 59% .