Do you trust completely the processes you were taught as a new brewer? You probably shouldn't. We all learned certain things that were claimed to be written in stone that later turned out to be completely or largely untrue.
How many of these myths are you still holding on to?
SQUEEZING THE BAG EXTRACTS TANNINS!
The one that I just recently heard that triggered this post is a myth that I thought was dead... finally. But apparently not is that squeezing the grain bag whether just steeping grains or mashing in a bag will extract tannins. This is FALSE. There are factors that contribute to tannin extraction like ph but squeezing the grains is not one of them.
BIAB LEADS TO LOW MASH EFFICIENCY!
This one is related to the previous myth. I and many others who began using the BIAB method 10 to 15 years ago all experienced mash efficiencies in the low to mid 60% range. Until that is we set aside the "squeezing the bag is bad" myth and started squeezing like mad. Using a fine crush, squeezing the bag and sparging with 1.5 to 2 gallons of hot water can bump that efficiency to 80% or better.
A SECONDARY STEP IS REQUIRED!
Not true. This belief goes back nearly to the beginning of homebrewing. It used to be thought that we needed to get the beer off of the yeast cake as soon as primary fermentation was complete to avoid off flavors and to promote clear beer. This myth was written about widely by authors many of us still revere as the master guru's of homebrewing. The trouble is that those same guru's changed their recommendations but those older books are still around and still tripping up new brewers. With experience and advanced learning we now know that you can leave beer in the primary fermenter far longer than previously thought without any risk of autolysis. Also, your beer will clear just fine without having to go into a secondary vessel. What has been learned also is that the risk of oxidation from moving the beer without extreme care is very real and far more harmful to your beer.
HOT SIDE AERATION WILL RUIN YOUR BEER!
This one is rather controversial. It has existed since I started brewing 20+ years ago. As a matter of fact it was this very picture posted over 17 years ago on the old Northern Brewer forum where I first heard the term. Being new to all-grain brewing at the time I believed all the comments shouting "Beware Hot Side Aeration!.
You still see comments like that on homebrew forums and part of the reason for that is that care to avoid hot side aeration is one of those commercial brewing practices that homebrewers believe they need to adopt. The truth is that not every process used at the commercial level applies to the homebrew level. Hot side aeration is one of those those. I would suggest that avoiding introducing oxygen at this stage is easy enough to minimize that you might as well do so but at the same time there is no reason to get worked up about it either.
