Hi Mister Clark,
That was me who replied to the thread. It's been a long time since I have had time to write on AHB but I saw this thread and as I had just answered a very similiar question to yours on another forum, thought I'd jump in. In my post, I asked you to read the thread on the other forum and then give me your numbers here as there are several critical ones we need from you before we can answer your question. Once you had given me your missing numbers, I was going to answer your question in depth and individually. This takes quite some time but I was certainly happy to do it. I will still do it, but it would certainly save me a lot of time if I could just have you read the other thread first.
My prior post here with the link to the other forum has been hidden by a Moderator. They advised me this was due to self-promotion. Whilst I do own the other forum linked, I have corresponded with the new owner of AHB on several occasions, and I don't think he would have minded my post, so maybe an administrator can check with him? Otherwise, I'll shoot him an email, attaching this post, to make sure I am not doing anything wrong. (I was also unable to find the AHB forum rules on a bit of search; the only post that came close to listing forum rules was
this one, which doesn't mention anything about self-promotion so it's probably all due for a refresh.)
Focussing on the Question
While we are waiting to determine if it is okay for me to refer you to the other thread, I will copy, very reluctantly now, the following list which I've compiled over nearly ten years. Most of the reasons below relate to all methods of all-grain brewing, although a few, relate to BIAB only. Have a good read of the below Mister Clark to see if anything immediately rings a bell.
Some Common Reasons for a Low Efficiency Reading
Firstly, never rely on a single reading on a single brew. An occasional strange reading is common. We, home brewers are trying to take measurements at a micro level. There's several points in the brew you can take gravity and volume readings so try and find two points on each brew until you have say 4 or 5 brews notched up. (And, don't be worried if you forget to measure. It's very hard for anything to go very wrong.) After say four or five brews, you'll develop an understanding of how much brew figures can fluctuate. So this is number one on the list below.
If an odd reading persists, points 2 to 10 below should be checked or re-checked.
1. Reading has not been confirmed. (This
table shows the resulting measurements of 30 brewers mailed identical ingredients and then asked to brew the same recipe.)
2. Grain bill incorrectly weighed.
3. Thermometer not calibrated at mash temperatures. (This
post shows how unreliable a single thermometer is.)
4. Hydrometer not calibrated at original gravity (or the brewer is taking gravity samples that are too hot to temperature correct.)
5. Bag is too small and restricts liquor flow. Your BIAB bag needs to fully line the kettle.
6. Bag porosity is too small. 35 vertical and horizontal threads per cm works well.
7. pH of mash has not been adjusted.
8. Estimated mash efficiency did not reflect the gravity of the brew. (A high gravity beer will have a lower mash efficiency than a low gravity beer. NOTE CAREFULLY: This point can be ignored if you are using the BIABacus as the BIABacus adjusts for gravity.)
9. The brewer is measuring 'efficiency into fermenter' rather than 'efficiency into the kettle.' The first figure is often far lower than the second.
10. The grain used has lower extract potential or higher moisture content than the specifications being used for the calculations.
11. Mash time is too short. In full-volume BIAB, mashing and sparging occurs simultaneously. Pulling your bag at 60 minutes, cuts this process too short. Allow at least 90 minutes and preferably follow with a mash-out.
12. The grain is not being agitated during the mash. Time, temperature and agitation are how we 'wash' things. Agitating the grain and checking the temperature several times throughout the 90 minute mash has no downside and should be done so as you can determine the cost of not agitating.
13. Volume being measured incorrectly. (Commercial container markings can sometimes be inaccurate. Always measure depth/headspace in the centre of the kettle.)
Let's see how we go with getting you sorted quickly.
:icon_cheers:
PP
