Cooling Shrinkage

[Midnight Brew]

Hey Brewers,

Brewed a batch yesterday on my BIAB system which gets me two cubes. This is a bit of a problem I've had in terms of target which Im slowly figuring out.

Hit pre-boil volume spot on, fell short of gravity by 1 point, no big deal. Get to the end of boil and hit post-boil volume spot on and measure gravity and I'm 4 points short. Im putting that down to the accuracy of my refrac but no big deal Im guessing its really 1 point short and the other 3 points are due to temp.

Now recently Ive been falling short of volume by 3-4 litres and I was initally putting it down to loss to grain, different boil rate and then the loss to the kettle. However for this brew these all appear to be spot on as I met my pre and post boil targets for volume. So this batch I fell short by 2L. Less then previously which is good so I went back and had a look at my figures. In this batch I had allowed for 4L of kettle/trub losses and 2L for cooling shrinkage. When I had finished filling my cubes I measure the left overs in the kettle and it was 4L, and I fell 2L short.

I am thinking my actual cooling shrinkage is about 8% (4.32L) instead of 4% (2.08L) which would explain the 2L.


Have I missed or possibly overlooked something or would I be corrent is thinking its a larger cooling shrinage rate?

How much cooling shrinkage do you allow for if you BIAB? (or any method of production)

 

[MHB]

It's 4%, that's a non negotiable number, a bit like gravity or the length of a meter, it cant change.
Well actually it isn't 4%, that's just a convenient approximation of the difference between the volume at boiling and at 20oC but you still cant change it.

You will need to go through your process carefully and measure the volume and temperature at every step, if you weigh your expended grain (if you weigh the bag first zero the scales with a bucket on them then weigh the bag and the grain, should be fairly easy) deduct the extract from the original grain mass and your mass of water should be fairly obvious.
The losses will be there somewhere just a matter of tracking them down
Mark

 

[Rodolphe01]

I account 4% for shrinkage and it work for me.

Different grains hold more wort than others, for myself if I am doing anything with wheat or flakes oat/rye etc I need to add much more water.

Different mash temps might also affect run-off? Lately I have been doing my BIAB mash with 11L less water, I then add the 10 litres at 100 degrees to achieve a mash-out of about 75 depending on other factors, this has improved my efficiency at least, not sure so much on volumes.

 

[Midnight Brew]

You will need to go through your process carefully and measure the volume and temperature at every step, if you weigh your expended grain (if you weigh the bag first zero the scales with a bucket on them then weigh the bag and the grain, should be fairly easy) deduct the extract from the original grain mass and your mass of water should be fairly obvious.
The losses will be there somewhere just a matter of tracking them down

Thanks for the feedback Mark. So leaving the cooling rate unchanged and at 4% is where Im struggling to find out where this 2L has gone. Because with a calculated loss of .628L (from a BIAB spreadsheet) per kg grain accounted for in my losses already, so really got me stumped as to how I lost 2L when I hit pre and post boil volume.

 

[tobyga]

May be a stupid question but how are you measuring your final volume to determine your 2L shortfall. I thought I had the same problem until I measured the actual volume of my 20L cubes and found they were more like 24L

Sent from my GT-I9505 using Tapatalk

 

[MHB]

Ok sounds interesting
lets leave the loss to grain aside for now, tho I would be a bit suspicious of that 0.628L/Kg number, I generally find its more like 0.8.

Once the sweet water is in the kettle we have all the extract there and that cant change unless you physically remove/loose some (samples, boilovers spillage...) so if at the start of boil you have the right mass of extract, at the end of boil there will be the same mass in less water and the density will have gone up proportionally.

If you are getting any other answer I would first up look at my measurements, how accurate are your volume markings, if for instance you were relying on the volume marks on the fermenter they could easily be out by 2-3L.
All my cubes in which I no chill have the mass on them, I fill them then weigh them giving me the mass of wort and calculate the volume from mass and density (sample at correct temperature) (i.e. 25Kg at 1.050 = 23.81L)
I really think you are looking for a systemic error, something where you are getting a miss read or bad data, have fun tracking it down.
Mark

 

[QldKev]

Also if you are cube'ing wouldn't the wort still be hot.

 

[Midnight Brew]

May be a stupid question but how are you measuring your final volume to determine your 2L shortfall. I thought I had the same problem until I measured the actual volume of my 20L cubes and found they were more like 24L

If you are getting any other answer I would first up look at my measurements, how accurate are your volume markings, if for instance you were relying on the volume marks on the fermenter they could easily be out by 2-3L.
All my cubes in which I no chill have the mass on them, I fill them then weigh them giving me the mass of wort and calculate the volume from mass and density (sample at correct temperature) (i.e. 25Kg at 1.050 = 23.81L)
I really think you are looking for a systemic error, something where you are getting a miss read or bad data, have fun tracking it down.
Mark

Initially as stupid as it sounds I did think a 20L cube held about 22L and thats because when I fill up the FV it goes to the 22L increment. So I just went downstairs put an empty cube on the scales and pushed tare then added my full cube 23.9kg and almost full cube 22.028kg = 45.95kg of 1.049 wort.

Mark what formula do you use to get that figure of liters from weight?

Think I've almost got this problem scaled out!

Also if you are cube'ing wouldn't the wort still be hot.

I assumed they held 22L. *Facepalm*

 

[Coalminer]

Try total weight minus empty weight then result divided by gravity

 

[MHB]

What he said
Mark

 

[Midnight Brew]

Thanks for the help guys, I've ended up with a cube at 22.8L and another at 21L so total of 43.8L turns out I was not short at all. I've taken heaps of notes and sorting out this little discrepancies helps me achieve a more consistent process. Made a few adjustments in my brewing software and kept notes of what I've changed in it so hopefully I've got all my numbers correct and not left confused again.

I had already accounted for kettle losses of an extra 2L due to the grain ration in BS2 being set to around .6L/kg, now changed kettle losses to actual losses and the absorption rate to .8L/kg.

So I think I've killed 2 birds with 1 stone and next batch the aim is 46L output (2x FULL cubes)

Thanks again will report back when I brew next.

 

[431neb]

I have two cubes from Super Cheap Auto (the blue ones) and I was amazed at how much they expanded when filled with hot wort. Initially I was doing some head scratching about volumes too.

As a side note - how much of a PITA is dialling in equipment profiles in BeerSmith? I lapse into a coma every time I look at it.

 

[Midnight Brew]

I cant believe I over looked the obvious. Left me head scratching when mentioned they hold more. I figured it would be 22L each not 23L and magic there was my 2L.

It's not that bad to dial it all in. I had been playing around with it for about 8ish batches and was getting more and more consistancy and by the end I had a good understanding of it all.

Whats got you going into a coma? What are you stuck on?

 

[431neb]

Whats got you going into a coma? What are you stuck on?

Just not got a head for figures Midnight. The terminology doesn't help much either. I find myself repeatedly looking up definitions to differentiate ( correctly) between the various volumes and efficiencies etc. I think I'm pretty much dialled in and the odd brew day anomaly is caused by brewer ( drinker) error.