Insane BIAB Efficiency after brewery revamp

[mtb]

That is where a refractometer is handy.

Yep, buying one next week.

 

[Lyrebird_Cycles]

I'd say that your issue is your adjustment for temperature.

I thought that too so I checked it and it's near enough.

I'm guessing MTB used the Brewer's friend calculator; it takes into account the variation in CTE with temperature rather than assuming a constant value of 200 PPM / oC.

 

[klangers]

Mmm, it is possible for the hydrometer, if cold, to reduce the temperature of the wort upon sampling, making the temperature to which one adjusts no longer relevant. That's the difficulty I've encountered personally anyhow.

 

[Lyrebird_Cycles]

Unlikely: weird factoid, the volumetric heat capacities of most solids are within 20% of a value of 3 MJ/m3, water is anomalously high at almost 4.2, glass is a bit low at 2.1. Combined with density, this means the specific heat capacity of glass is about one fifth that of water.

The mass of the hydrometer is by definition equal to the volume of fluid displaced, in a normal scenario with adequate clearance between hydrometer and bulb the hydrometer represents about one quarter of the combined mass of the system. Accordingly, a 40 degree difference in temperature between glass and sample would equilibrate out to a temperature drop of about 2.5 degrees.

Before anybody asks: the linear CTE of borosilicate glass is about 3 ppm and more or less linear with temperature so the resultant expansion of the hydrometer is not material.

 

[klangers]

Yes I am aware of that, but you forget the lead mass at the bottom of the bulb.

Unlikely, but has happened to me before - possibly a combination of multiple errors - error in temperature, error in calculator, some temperature loss upon sampling, temperature loss as the hydrometer equalises and slowly disspates heat.

Possible to all add up to the error experience by the OP.

 

[n87]

Before anybody asks: the linear CTE of borosilicate glass is about 3 ppm and more or less linear with temperature so the resultant expansion of the hydrometer is not material.

Lucky you mention that... otherwise i may have pulled you up on it :unsure:

 

[mtb]

I'm guessing MTB used the Brewer's friend calculator; it takes into account the variation in CTE with temperature rather than assuming a constant value of 200 PPM / oC.

Correct, I used Brewer's Friend.

Mmm, it is possible for the hydrometer, if cold, to reduce the temperature of the wort upon sampling

I took wort temp from the hydrometer tube itself via an STC-1000 probe

Unlikely: weird factoid, the volumetric heat capacities of most solids are within 20% of a value of 3 MJ/m3, water is anomalously high at almost 4.2, glass is a bit low at 2.1. Combined with density, this means the specific heat capacity of glass is about one fifth that of water.

The mass of the hydrometer is by definition equal to the volume of fluid displaced, in a normal scneario with adequate clearance between hydrometer and bulb the hydrometer reresents about one quarter of the combined mass of the system. Accordingly, a 40 degree difference in temperature between glass and sample would equilibrate out to a temperature drop of about 2.5 degrees.

Before anybody asks: the linear CTE of borosilicate glass is about 3 ppm and more or less linear with temperature so the resultant expansion of the hydrometer is not material.

Great bit of knowledge there mate - I'm always sure to watch out for your posts..

 

[Lyrebird_Cycles]

Yes I am aware of that, but you forget the lead mass at the bottom of the bulb.

The specific heat capacities of lead and bismuth are around 1/40th the value for water so including them in the calculation reduces the error. If the intention is to show that the error is small it is usual to go with the largest possible error (worst case scenario).

That's why I mentioned the volumetric heat capacities all being in a narrow range: this means the specific heat capacities of dense materials tend to be very low.

 

[Rocker1986]

I just stick my pre-boil sample in the fridge as soon as I take it, it's down to around 20C in a couple of hours or less depending on what temp it started at. I have borosilicate glass testing jars which makes it easier I suppose.

The post boil sample I take into a 500mL pyrex jug after transferring the wort to the cube and just leave to sit on the bench for a few hours to cool down before taking a reading. It's usually full of hot break so this allows that to settle and get a clear wort sample too.

 

[klangers]

The specific heat capacities of lead and bismuth are around 1/40th the value for water so including them in the calculation reduces the error. If the intention is to show that the error is small it is usual to go with the largest possible error (worst case scenario).

That's why I mentioned the volumetric heat capacities all being in a narrow range: this means the specific heat capacities of dense materials tend to be very low.

I agree with you on that. I was more trying to be a smart arse splitting hairs with your very thorough post.

I think we both know there's more to it than specific heat capacity differences. There's definitely more to it than simply the thermal mass of the submerged hydrometer. How the wort gets poured into the hydrometer and sample jar means that it can mix with the air, contacts the side of the jar which the brewer might be holding etc etc.

We can be going to and fro about the details, but at the end of the day if all other inputs check out,the most obvious thing to me is that the temperature that was plugged into the calculator was wrong or at least not representative of reality at that point in time.

 

[dr K]

My first thought was that the kilo bags weighed somewhat more than a kilo. Looks like you should be buying more milled bags from that shop !!!
Your pre boil volume was estimated I know but if your wort was 3cm below the top of a 70litre pot thats hardly enough wiggle room for expansion let alone rapid boiling.....
but you had a rapid boil and still ended up with 60 litres?
What obvious point am I missing.??

K

 

[mtb]

Just finished sparging a new batch. Same high pre-boil reading as the last brew - 1.066 whereas the recipe calls for 1.056 with 80% BH efficiency - So I dug out another hydrometer I had lying around and took a reading from the same sample of wort, cooled to room temp, in two separate hydrometers.

Same reading on both.

I'm going to push ahead and see how it ends up.. strange that two hydrometers are a) incorrect/faulty and b} have the same margin of error. Yes, they're calibrated to 20C.

 

[SBOB]

is it possible your measurements elsewhere are off.. i.e. volumes?

 

[mtb]

Thought that, but I measured. 2L under predicted volume

 

[Lyrebird_Cycles]

Any chance the hydrometer doen't have enough clearance in the tube? Ideally you want the ID of the tube to be twice the OD of the hydrometer or more.

An easy test for this is tow take two readings, one by letting the hydrometer settle and then gently lifting it a cm or so and letting it resettle, the other by pushing it down by a cm or so and letting it resettle. Ideally you'll get the same reading both times.

 

[mtb]

Gave that a go (I saved a pre-boil gravity sample in case). Same reading.

It looks like I hit my targets after all - 83% BH efficiency, it seems that I'm just three points under target OG but a couple litres over target volume. I'd say Beersmith was just giving me funky target pre-boil gravity targets, I'll tune it to accommodate

 

[contrarian]

Just had a look at you beersmith file and your boil size is bigger than your kettle with you batch size only being a few litres short of your pot size.

So you say your pot is 50L but your boil size is 15.13G which is 57.273L and your batch size is 12.13G or about 46L.

I'm guessing this has something to do with your sparge and when you are adding this in but I think if you sort this out the gravity readings you are getting will make more sense.

 

[mtb]

Just had a look at you beersmith file and your boil size is bigger than your kettle with you batch size only being a few litres short of your pot size.

So you say your pot is 50L but your boil size is 15.13G which is 57.273L and your batch size is 12.13G or about 46L.

I'm guessing this has something to do with your sparge and when you are adding this in but I think if you sort this out the gravity readings you are getting will make more sense.

My pot is 70L - must've left the equipment profile at the 50L setting. Possibly a contributor to my issues but I wouldn't expect there to be a huge difference in equipment stats (ie boil off rate) between a 50L and 70L pot

 

[Rocker1986]

Well, the OG is 1.049. No clue what prompted the hydrometer to read so high pre-boil... I **** you all not, it read 1.048 pre-boil, with adjustment for temperature, that was 1.061.

This taken from the first page. Something is wrong with your pre-boil readings. You can't end up with a lower SG after the boil. Buggered if I know what it is though.

 

[contrarian]

That makes more sense but I still think it is difficult to pull 46L out of a 70L pot. I have the same set up and normally manage about 40L into cubes with about 5-7L of boil off over 60min and about 5L of trub loss.

I have managed 3 15L cubes of 1.045 pale ale but that was really pushing the system to its limits.

So is the 46L your post boil volume or are you getting into your fermenter?

 

[mtb]

I hit 50L into the fermenter. I wouldn't be able to achieve that if I BIAB'd with the full volume as mash water - simply not enough space in the pot - so instead I have 40L water for my mash, and then sparge with the other 24L to hit 66L pre-boil volume. This kills two birds with one stone as I can sparge and get the high BH efficiencies I'm after, while also topping up the pot after removing the grain bag and clawing back headspace.

 

[contrarian]

Are you topping up with water or with sparged wort?

It might be worth checking the gravity of the running a from the sparge to see what that is contributing as adding volume of lower gravity wort to the boil could be diluting it along the way which could explain a drop in gravity.

 

[mtb]

Topping up with sparged wort.
I only sparged with as much water as was required to achieve the pre-boil volume as per the recipe. I suspect that the grain didn't retain as much water as Beersmith expected, which would've caused it to dilute the wort and cause my slight OG undershoot & excess volume

 

[contrarian]

Next time you brew measure the gravity of your sparged wort as it will make a difference that can be calculated.

It will also make it a bit more difficult to measure your evaporation, not impossible, just more challenging.

If you keep your process the same over a few brews then you will get the hang of it fairly quickly.

 

[mtb]

Sounds good, thanks for the input. I just started sparging so will put a few batches down and see how I go.

Gotta love that BH efficiency though, 83%!

 

[contrarian]

I'm not that driven by efficiency. As long as I am relative consistent for similar gravity brews it means I can replicate things reasonably well given the variable in the home brew environment!

Brewhouse efficiency also is impacted by losses to grain absorption and trub. I don't have a pick up tube so always lose a few litres there which drops it by a few points!

In probably far too casual in my approach to brewing (with the exception of cleaning) but that's the way I like it and I'm happy with my beer!

 

[mtb]

Consistency is definitely preferable - my issue now lies in consistency - but it's nice to be able to get an extra 15% efficiency with very little effort. My sparging solution is very ghetto; I just drilled a bunch of holes in the bottom of a fermenter, cut the top off, put the grain bag in there after mashout, and dump the sparge water on top from a $40 hot water urn I found on Gumtree. It sits on a wire basket atop my BIAB pot so the runnings dump straight in.

 

[huez]

Get yourself a long steel ruler and use it to calibrate the volume of your pot, fill it up one litre at a time and mark the ruler or take note of many mm one litre is. I doubt your pot is exactly 70 litres. Your volumes seem to be all over the place. I'd be looking at some of your settings in beersmith as well, grain absorption, pot sizes, dead spaces, boil off rates etc. Change one at a time and take notes. Doesn't really explain your initial high reading though, somethings whack, keep brewing until you get it right!

What kind of voodoo are you using to stop a boil over with an almost full pot?

 

[mstrelan]

Get yourself a long steel ruler and use it to calibrate the volume of your pot, fill it up one litre at a time and mark the ruler or take note of many mm one litre is. I doubt your pot is exactly 70 litres. Your volumes seem to be all over the place. I'd be looking at some of your settings in beersmith as well, grain absorption, pot sizes, dead spaces, boil off rates etc. Change one at a time and take notes. Doesn't really explain your initial high reading though, somethings whack, keep brewing until you get it right!

+1 for this. If you have the same pot as me from Craft Brewer I measured it out to be approx. 6.4mm per litre, by filling it 2L at a time using a jug and a set of scales. From memory, the pot dimensions are 450mm diameter x 450mm depth. Using maths that equates to 71.569L.

 

[mtb]

Sounds like I'd better get to work verifying the volume of my pot.

No such voodoo here, I've never had to actually stop a boilover, I've never had one start to occur. When I do my boil I run the 2400W element and gas burner on low, then slowly ramp it up til I'm getting bubbles breaking the surface, and I leave it there. Maybe I'm not boiling hard enough h34r:


My pot is actually 71L according to the invoice from CheekyPeak. That'll learn me to approximate. The metal ruler idea is good though.. I could etch volume markings into it with my Dremel. Entirely unnecessary but I just can't stop myself using that thing