Tomas,
If your BIABacus quantities are accurate and your grain has been milled then make sure that the grain bag is protected from scorching.
Try to maintain mash temperature within a degree or two of  required temperature by firing the kettle as needed and agitate your mash often.
Insulating the kettle will help. You may need to remove the insulation when the burner is on. Be cautious.
Wort should be cooled to around 70 F for an accurate specific gravity reading.
90 minute mash or maybe even longer.
Attention to these details work for me. Opinions and techniques will vary. I think this is a good beginning.
Good Luck, Cheers!

I use the same type of blanket.
I think that stirring the mash helps to extract the sugar from the grain.
I would try stirring more and adding heat as necessary to maintain temperature.

I think R64 is correct, and I've struggled with this same issue. Stirring or agitating the mash would, I think, accomplish two things: help assure that the grain is adequately washed so that the sugars from the grain are disbursed, and keeping the temperature uniform through the liquid. I see that you have a stationary thermometer - I would think if you don't agitate the sweet liqueur often, you'll end up with areas that are cooler and others that are hotter, so you can't be sure that you are maintaining a consistent temperature throughout. You also said that you dropped the temperature by 10F over 70 minutes (if i'm interpreting this correctly). From what I've found on this forum, you should try to maintain as constant a mash temperature as reasonable. So agitating the liqueur often should help you monitor the temp.  I haven't found a good insulation product to use, so I monitor my temperature after agitating every 5 minutes or so (roughly 7 gallons), and fire up the burner as necessary. When I fire up the burner I stir constantly and take temperature readings until I get to my target. I think I'm restating things that have been better said, but hey, I'm retired (sort of). Refer to "The Commentary" for the best discussion of this [font=Verdana, Arial, Helvetica, sans-serif] [/font]http://www.biabrewer.info/download/file.php?id=51
[ltr][font=Verdana, Arial, Helvetica, sans-serif]The Commentary.pdf[/font][/ltr]
starting at "mash".
I'm really interested in your insulation technique. Did you buy it at a big box or on line?

Thanks Thomas. I think I'll go buy some reflectix. It looks like it would help keep the heat in. Definitely better than none at all.

Thanks Thomas. I think I'll go buy some reflectix. It looks like it would help keep the heat in. Definitely better than none at all.

Streamer, When cutting your Reflectix, consider over lapping the ends.
 Mine was cut a few inches longer and secured with velcro. 
When I left it on and applied low heat to the kettle it did shrink buy 3/4" in length.
The bottom edge also began to shrivel. I may cut the bottom shorter and add an outer layer.
A roll of Reflectix at Home Depot is 2' x 10'.
Tomas,
As other members on this site recommend measuring temperature in more than one area of your kettle. A calibrating and a instant read thermometer make a good combination. 
The Mad Scientists method of mashing with a large potato masher is a good way to agitate the mash. 
I use these methods each time I brew and always reach the required gravity. 

I use an old comforter secured along the bottom with a bungee cord. I also wrap the burner stand 3/4 of the way around with aluminum foil. Wrapping the sides will not do much unless you insulate the lid. The foil keeps wind off the bottom and makes the burner more efficient.

I maintain mash temperature within 2°F for a 90 minute mash with 2 stirs.

Tomas wrote:[sup]Primavera - Thanks. Are you maintaining the 2 degree variation without firing up the burner? Are you brewing outdoors with a gas hired burner?[/sup]

Yes and Yes

The comforter is purple on one side and polka-dot on the other. I believe that is why it is so effective.

Seriously though - it is a double layer of thick insulation covering the entire kettle and the bottom is shielded from wind with the foil. The bungees secure the bottom of the comforter leaving everything above loose. I am usually at ±0°F after 30 minutes and -0° / -1°F at 60°F. This is for 10.5 gallons of water and 15# + of grain.

Hey Tomas,

A couple affirmations...along with some additional.

1) Agitating the mash is very important for good BIAB efficiency. I agitate really well with potato masher when first mashing in, then twice in middle step of 90 minute mash, and again immediately prior to pulling bag and starting the boil Actually two mash agitations with middle step of reheating process at roughly 45 minutes, in middle of mash: a) agitate mash, b) pull bag partially / off the bottom of pot and reheat, then c) lower bag back into wort, then d) agitate mash again prior to e) re-covering pot with insulation... So I stir / agitate the mash at least 4 times total throughout the mashing process...very thoroughly. 

2) Insulation - I wonder if your aluminized material will insulate enough...? Maybe. Just depends how cold it is outside. It looks really nice. Here is my process... A) use a cotton based blanket folded once lengthwise to wrap the pot with the excess folded and put on top the pot. B) wrap with similar size synthetic blanket folded same way. (Don't use synthetic against hot pot and burner.)  C) wrap with old sleeping bag. Use a couple paper clamps to hold it on. I normally will lose 2-3 degrees during this time. And remember that if it is cold, a pot thermometer read from outside will likely be a couple degrees colder than the temperature in the middle of the pot. 

Remember that "dead air space" is actually what does the insulating, and not the material that holds the "dead air"...

FYI Some people use a smaller size pot lid inside and at the bottom of their the pot, with holes drilled in it. Then don't cover the pot during the mash, using low heat and not pulling the bag... Then apparently pull the lid before the boil... I have no practical experience doing this.

3) Efficiency - the number on the BIABacus is always close. Plus or minus a couple points, with it being over more often than under. It is not some kind of vague number not to be achieved. 

Certainly I remember the confusion of what to do, processes, when I was new. Asked a lot of questions on this forum and received great advice. There are multiple ways to get a good result. But if you are copying someone, it is best to model someone that is doing it right and getting the proper result. Best of luck and hope this helps!  

Great explanation Scott. I just picked up an old comforter today (synthetic cover, not cotton) and was worried about placing it against the hot brew vessel. The cotton towel is too simple! Now I just need to find a potato masher that didn't belong to my mother-in-law (because it's sacred) and I'll be set    

Scott wrote: ↑

7 years ago

I agitate really well with potato masher when first mashing in

wrap with old sleeping bag.

I use a paint stirrer which looks much like an oversized potato masher, it works brilliantly and the length is spot on for my urn depth, however my search continues for a Stainless steel version.

+1 on the sleeping bag. I've never had an problems with using one and only lose about 1dC over a 60-70min mash. Plus when I go camping I get to enjoy to aroma as I drift off to sleep.