Trying to Determine Why OG Was .004 Low - Volumes and Pre-Boil Gravity Spot On

I brewed yesterday and ended up being .004 low on my OG target. I suspect it was due to higher water volume but I can't really determine where the issue resides because I hit my water volume targets as well as my pre-boil gravity.

I could see if the pre-boil gravity was low or if my post-boil volume was high but they were right on.

Any suggestions on what to look for?

Also, will being low by .004 (1.044 vs 1.048 target) have much of an impact on my final beer flavor and/or mouth feel?

What was your pre-boil volume and gravity?  Your post boil volume and gravity?  It's hard to diagnose where things may have gone off without any numbers to follow your process through.

Right off the top of my head, I would suspect that one of your readings is off a bit if you hit your volumes and pre-boil gravity just fine.

My opinion is that .004 is really not a whole lot to be concerned about.  This difference may have been caused by a miscalculation either when measuring Pre-Boil or OG.....in that you would have had to calculate the readings using a temperature conversion calculator and even one degree can make a difference of .004.  As far as the impact, I would say "no" to both flavor and mouth feel.  However, your ABV MAY be slightly lower, but that depends on many other factors at play as well.

My grain bill was:
3.5# Wheat Malt
2.5# 2-Row
.2# Honey Malt
2# Honey at flame out

Boil Volume 6.9 gal
Pre-Boil SG 1.027
Post Boil Vol 5.9 (After adding honey and chilling)

So, going through your numbers:

You have 6.9 gallons at 1.027 sg pre-boil.  This gives you 186 gravity points (6.9 * 27).

Post boil, you added 2 lbs of honey (density of 1.42), so that works out to be 907/1.42 = 639 ml or 0.17 gal of volume

You ended up with 5.9 gallons of wort, .17 gallons of which was honey, so that is 5.73 gallons.  Your SG post boil should have been 1.032 (186/5.73 = 32).

You ended up with 5.9 gal at 1.044 or (44 * 5.9) 260 gravity points with the honey added.  the difference: (260 - 186) = 74 is the amount of gravity points added by the sugar.  This means the gravity contribution of the honey was 1.037.  This is well within variation that I have found with the types of honey I have used so far.  I've seen bulk clover honey come in at 1.034, and up to a friend's honey which gives me a contribution of 1.041. 

That's most likely where any 'issue' may be hidden.

I appreciate the detailed response. This will help me to understand the process moving forward.

I wish I had taken a sample of the wort before adding the honey. That would tell the whole story, wouldn't it?

I didn't consider that honey could have variations. How fo Brewers account for this in order to achieve consistent results with recipes that use honey?

It makes me feel better knowing the issue likely doesn't reside in my water volumes. Gives me hope that I may be closer to dialing in my system.

Honey is a complex mixture of sugars and other materials.  I've taken 1.000 grams of honey, diluted that to 8.344 grams with water and used a refractometer to give me the brix reading.  Even then, there is some variation because of the different glucose:fructose ratios and ability of the refractometer to accurately read those sugars.  There are also maltose, sucrose, and dextrins in varying amounts depending upon source.

And you are correct, a post boil gravity (pre-honey addition) reading would have helped you figure this out. 

One question.... I'm not clear how the honey addition contributed 1.037?

The honey did not contribute 1.037, the potential is 1.037.  My poor wording.

The 2# of honey contributed 74 points, which is 37 points per pound, thus a potential of 1.037

I guess what confuses me is I interpret that as potentially 1.027 + 1.037 = 1.064

Jiffster said:

I guess what confuses me is I interpret that as potentially 1.027 + 1.037 = 1.064

Click to expand...

Gravity potential is what 1 lb of a sugar source would yield as 1 gallon of liquid. You have honey with a potential of 1.037 per lb and you're using 2 lbs. That's the 74 points Oginme was describing.

To get how much gravity rise the honey contributes to the recipe, you need to divide by the batch size in gallons. That comes to 1.013

So the potential would be 1.050, correct?

No, the potential is the number of points the honey adds per lb of honey added.  The 2 lbs of honey added 74 gravity points which makes the addition per lb 74/2 or 37 points per pound.  The potential is the gravity points per pound divided by 1000 and then add 1:  37 / 1000 +1 = .0037 + 1 =1.037