Hey Nick, I've been wondering how you've been getting along with this?
I should have mentioned earlier, always post your file up with your actuals as then it makes things much easier to analyse. For example in your post above, we know you had 1 litre of nasty trub (Kettle to Fermenter Loss) but we don't know what the BIABacus predicted. You also mention your Gravity into Boil but not the Volume into Boil. Remember the volume and gravity 'sets' I mentioned? Both the volume and gravity measurements are needed at the same point in time for us to find process errors.
The most important sets to take are...
Volume and Gravity into Boil:
Easiest way to do measure the volume is after you pull the bag. It's much easier to measure the volume at mash temp than when it is boiling. Whatever volume you measure at mash temp, increase it by 2%. This is the "swelling" that occurs between mash and boiling temp. If you've collected running from the bag after you've pulled it, pour them into a calibrated jug and add that volume. With your gravity into boil, grab a sample in a thin stainless bowl after you've pulled the bag. Cover in wrap and put it in a water bath until it reaches 15 to 20°C. Don't measure it hot!
Entering the VIB and GIB will make your Efficiency into Boil show up in Section P.
Volume and Gravity of Ambient Wort:
Easiest way to measure the volume is to measure the Voume into Fermenter (VIF) and, after transfer, pour all the kettle trub into a calibrated jug to determine your Kettle to Fermenter Loss (KFL). VIF plus KFL = VAW. I tend to take two gravity readings. One I grab at the end of the boil using the same method as for Gravity into Boil. I then grab another as I transfer into the fermenter. These "Gravity of Ambient Wort" measurements should both match and give me confidence in what, if any, pre-pitching corrections I shuld do to acheive my desired Original Gravity (gravity at pitching).
Entering KFL, VIF and GAW will make your Efficiency of Ambient Wort and Efficiency into Fermenter show up in Section P.
Taking the Above Sets Reveals a Lot
Doing the above can narrow down problems very quickly so they are essential to do when you are trying t work out the source of a problem.
A Few Other Things
I noticed in the BIABacus files you posted in your first post that your Mash Volume is lower than predicted. It should be usually closer than that. It looks like you are measuring the volume before you add the grain. It should be measured after the grain is added.
Besides taking the volume and gravity sets mentioned above, the other critical thing in your situation is to find two different methods of measuring in your water and grain. It is not uncommon for scales or volume markers on vessels to be out so...
Total Water Needed: From a jug you know is calibrated correctly (put it on scales and make sure adding 3 litres of water to it increases the weight by 3000 grams) us that jug to fill your kettle. After that, measure the depth or headspace in the kettle and see it matches the BIABacus. If not, why?
Volume into Fermenter: Same thing again. Add water from the above jug and make sure it matches the markings on the fermenter.
Grain Bill: If you've bought it pre-packaged, weigh it on your bathroom scales. If you're weighing it yourself, firstly, double-check your scales match another set. Ask a neighbour to compare scales or something? If your scales are correct, weigh your grains individually and pour them into a bucket (after weighing the bucket). Once all grains are added, weigh the bucket and make sure everything adds up.
The above might seem like obvious advice but I have a calibrated jug here, bought from the supermarket, but was astounded to find that when filled to the 4 L mark, it actually only holds 3 L. What the...??? I've had other brewers swear that they had weighed their grain correctly only to later find that the 1kg bags of grain they bought from the shop were actually only 500 grams. It's amazing the funny ways we can get caught out!
Finally, you must ensure that you don't rely on one thermometer for mashing or on one hydrometer for measuring gravities.
Looking forward to hearing your next update
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