I apologize for the length of this, but I feel like I need to explain the background for my question. Prior to performing my first BIAB, I posed the question about possible grain bill adjustments when brewing a typical beer recipe by BIAB as opposed to traditional 3-vessel. That question was based upon rumors that BIAB was less efficient than 3V. The consensus was that this was false and that no adjustments are necessary.

I'm adding another layer to the complexity - doctors like to do that - by pulling a couple quotes from Kal's website: http://www.theelectricbrewer.com. FYI, Kal has published plans for the 3-vessel brewer to go completely electric. In his section entitled "Brew Day: Step by Step" he gives the following explanation for his mash temperature for the particular recipe:

[set temp to] 149F. This is the mash temperature for our recipe. We are mashing at a fairly low temperature in order to produce a wort that is more fermentable which will leave us with a dryer and lighter tasting beer. Mashing at higher temperatures results in less starch to sugar conversion leaving a beer with a fuller body and flavour.

A few pages later he describes the liquor:grist ratio as follows:

Like mash temperature, the water to grain ratio (often called 'liquor to grist ratio') used when mashing also affects the beer you produce. Generally speaking, a thicker mash (less water) produces a beer that is fuller/sweeter as it creates more unfermentable sugars while a thinner mash (more water) produces a thinner/dryer beer as it creates more fermentable sugars.

This mash thickness is usually expressed as the number of quarts of water per pound of grain. . . .

So my take on those two variables is:
Regarding temperature of the mash:
Lower = more starch conversion > more fermentables = dryer, lighter beer
Higher = less starch conversion > less fermentables = fuller, more flavor

Regarding thickness/thinness of the mash:
Thicker = less conversion = fuller, sweeter flavor
Thinner = more conversion = thinner, dryer beer.

So my theory - based upon study as opposed to experience - is that the 3 beers resulting from same recipe would not be exactly the same when brewed by the following brewers:

1. traditional 3 vessel brewer
2. full volume BIAB brewer
3. maxi-BIAB because his kettle is not large enough

Since full-volume BIAB uses a much thinner mash, a given recipe should result in a dryer, lighter beer than if it were brewed on a 3V system.

The recipe might be identical if the maxi-BIABer used the typical liquor:grist ratio as the 3V brewer. But my take on maxi-BIAB is that you mash at whatever volume your kettle will handle - which still might be thinner than 3V mash - and simply sparge with the remainder of your full volume, adding it to the kettle as it boils down.

So, my thinking is that full volume BIAB brewer must mash at a higher temperature than the 3 vessel brewer in order to get the same conversion. The maxi-BIAB brewer must mash at a temperature somewhere in between depending upon his liquor:grist ratio. I know I'm making things much more complicated.

Has anyone experimented with the volumes and temps to come up with any sort of relationship between the two variables for a given conversion?

For example if I'm going to brew 5 gallons of beer with O.G. of 1.062 in a 16" diameter pot, the maxi-BIAB calculator gives the grain bill as appr. 12 lbs . . .

1. 3-vessel brew would mash with 1.2 qt/lb = 14.4 quarts (appr 3.5 gallons)
2. full volume BIAB would mash with 9.12 gallons.

So, if the 3V brewer were mashing at 149*F, the BIABer would end up with a much dryer and thinner beer. Is there any conversion factor to apply that would give the BIABer the exact same beer profile from the recipe?

Please don't respond with RDWHAHB, hee hee.

Thanks,
Keith

joshua wrote:Keith, Your question is right on, I think.....
<snip> Mashing as low as 140F/60C Will give to a Bone dry beer, and as high as 158F/70C will yield a thick sweet wort.
. . .
Your Comment of 149F/65C is on the dry side, is far from the dryest you can go, mashing at 152F/67C yields the highest effiency/conversion.
<snip>

Thanks, Joshua. So let say that I wanted to brew an AG recipe of a beer that I really liked. It was designed for a 3 vessel system and called for a 1.2 qt/lb liquor:grist and is to be mashed at 149*F. If I did it by BIAB, that ratio is now 3 qt/lb if I do full volume. Wouldn't the resulting beer be much dryer and lighter than the one I liked?

So my thinking is that I would correct for that by mashing at a higher temperature. I was wondering if there was any published "correction factor". IOW, if I mash at a ratio that is "x" times the original, I will raise my mash temp by "y" degrees.

It seems to me that guys doing maxi-BIAB would come closer to duplicating the actual beer represented by the recipe than those doing full volume BIAB unless there is some sort of correction of the other variable (temp, in this case).

My guess is that there's a range that various brewers follow, and that it's more related to a "gut feeling" than an actual calculation. For example:

1. the 3-vessel brewer may almost always mash at a certain temperature and, therefore, adjust the full/thin and sweet/dry by changing the liquor:grist ratio. "I generally mash at 149*F, so, if I want a dry beer, I will use 'this much' water per pound of grain, but, if I want a fuller, sweeter beer, I will use 'that much' water per pound."

2. the 3-vessel brewer may almost always mash with a certain ratio, but adjust the full/think and sweet/dry by changing the mash temp. "I generally mash at 1.2 qt/lb. If I want a dry beer, I mash at 'this' temp; if I want a fuller sweeter beer, I mash at 'that' temp."

3. OTOH,for the full-volume BIAB brewer, the L:G ratio is determined by the total water needed for the entire brew, so the only factor s/he can adjust would be the temperature. "I do full volume mash and tend to mash in the following temperature range. If I want a dry beer, I'll mash at the lower end of this range; if I want a fuller, sweeter beer, I'll mash at the upper range."

I'm wondering if those of you who have been doing BIAB for a long time - and, possibly, 3-vessel for years prior to that - have subconsciously made adjustments to your old recipes and, based on your gut feeling, have adjusted your mash temps accordingly. So, you look at a recipe for some clone you want to do and you just "feel" that you should mash at a particular temperature to get the beer you want?

Again, I might be over-thinking this.

Thanks,
Keith