OG Question

[IchLiebeBier]

Hi all,
Today I brewed the AG Better Not Pout Stout recipe on the BYO site (for a work Christmas Party). It was the first time I used a refractometer, too.

I followed the recipe exactly, and hit my 70% efficiency goal at 7 gallons, which is what my Brew Pal app is set at and the volume the recipe calls for. So, at this point, everything was lining up with the recipe and the Brew Pal. I calculated the boil off, and it put me at 5.15 gallons to hit the 1.068 OG. All efficiency calculations were done based on grain only (no honey).

However, once I added the honey, it shot the gravity reading up a good 10 points (1.058 to 1.068, if that's 10 points). By the time the boil was complete, I ended up with 1.075 OG. I wasn't overly concerned, because I had enough yeast to pitch, so I figured I'd just end up with a stronger beer.

My question is, what would have happened to shoot the gravity up so far above the calculations if everything lined up according to the recipe? With the honey, the Brew Pal was calculating everything to add up. Could it have been that I added the honey under fermentables and not under other ingredients? Or could the refractometer have been affected by the honey for some reason I don't know about?

Any ideas would be appreciated, because I'm stumped.

 

[Riot]

If you hit your target gravity preboil it looks like you had better than the target %70 efficiency. If the gravity is higher than you want it you could top up with water if there is room in your fermenter. Or just let it ride out high proof.

 

[IchLiebeBier]

If you hit your target gravity preboil it looks like you had better than the target %70 efficiency.

Maybe, but I was showing a couple of guys how to homebrew, so I think I was pretty careful with the measurements. I used the Brewer's Friend site efficiency calculator and ran the numbers off the grain bill and the 7 gallon collect. As long as I read the refractometer correctly, I was right on 70%.

The only thing I can figure is that the recipe was built under the app with honey as a fermentable, and it thus calculated the gravities with an assumed 70% efficiency WITH the honey added in.

But overall it still doesn't add up to me, since I was right on line with the grain bill, as well as the starting/ending volumes as stated in the recipe. I assume the recipe creator based his mash on 70% as well.

 

[kev]

I use Pro Mash software, when it comes time to take my pre oil eff. readings it wants me to do it after all fermentables are in the kettle. My guess is that the recipe calculated 70% with the honey. Did you happen to take a preboil gravity reading with the honey? If so rework your numbers. I think that your eff. is greater than 70%. Hope this helps.
Cheers
Kev

 

[IchLiebeBier]

I finally hit on the proper google search, and I'm beginning to think that the viscosity in the honey may affect the light pass through and throw off the reading on the refractometer.

Maybe with honey in the recipe, you should always use a hydrometer?

Any thoughts?

EDIT: Just tested it with DME and honey. At 68º wort temp (calibration temp for the refractometer) and about 70º room temp, here are the results: hydrometer -- 1.068 corrected // refractometer -- 1.073. Incidentally, this just happened to be very close to the results of the recipe for me.

EDIT 2: Just tested DME only. Same specs. hydrometer -- 1.041 corrected // refractometer -- 1.042. Maybe should have used enough DME to get to 1.068 for comparison, but I doubt it would make a difference in reality.

Totally unscientific test, but I'm beginning to believe that honey throws off the refractometer. It may also be thrown off with syrup and candi sugar, too. If so, I'd say folks using those ingredients should potentially stick to a hydrometer for accuracy sake.

I wish I would have taken the OG reading with a hydrometer for comparison. I'll do that next time I brew a Belgian.

 

[kev]

I finally hit on the proper google search, and I'm beginning to think that the viscosity in the honey may affect the light pass through and throw off the reading on the refractometer.

Maybe with honey in the recipe, you should always use a hydrometer?

Any thoughts?

EDIT: Just tested it with DME and honey. At 68º wort temp (calibration temp for the refractometer) and about 70º room temp, here are the results: hydrometer -- 1.068 corrected // refractometer -- 1.073. Incidentally, this just happened to be very close to the results of the recipe for me.

EDIT 2: Just tested DME only. Same specs. hydrometer -- 1.041 corrected // refractometer -- 1.042. Maybe should have used enough DME to get to 1.068 for comparison, but I doubt it would make a difference in reality.

Totally unscientific test, but I'm beginning to believe that honey throws off the refractometer. It may also be thrown off with syrup and candi sugar, too. If so, I'd say folks using those ingredients should potentially stick to a hydrometer for accuracy sake.

I wish I would have taken the OG reading with a hydrometer for comparison. I'll do that next time I brew a Belgian.

I have never used a refractometer before, but it is possible depending what kind of honey you are using, the kind of candi sugar ( light/dark), how thoroughly mixed it is. If your sample had more honey than wort I could see that.
Cheers
Kev