First 2 Batches Partial Mash: Both lower than expected OG. Ideas?

I have just jumped from doing Extract for the past 2 years or so, to partial mash recipes.

I brewed a Budget Pale from Austin HomeBrew Supply. I was able to keep my mash pretty close to 155 for 45 minutes. Sparged with 2 qts. at 170. Did all the rest as a normal extract. OG was supposed to be 1056 and I got 1047

Second batch I brewed was their Hop In The Dark clone. Mash at 156 - 157 for 45 minutes. Sparge 2.25 qts at 170. OG was supposed to be 1067 and I got 1057.

I have no idea what I could be doing wrong as I'm following the recipes to a T. The only thing I can think of is possibly my grain bag is too small and its not letting all the fermentables out of the grains when i mash? The bag holds 4.5 lbs of grain and I can tie it closed, but it's a pretty tight squeeze.

Any ideas?

Did you calibrate your thermometer beforehand? If it is reading low by 4 or 5 degrees, it could be pushing you out of the temperature range for mashing.

Actually, now that I think about it. No.

I just purchased one of these before I started partial mash. I'll have to test it in some boiling water later today to see if that's the case.

davidg410 said:

Actually, now that I think about it. No.

I just purchased one of these before I started partial mash. I'll have to test it in some boiling water later today to see if that's the case.

Click to expand...

I would test it against an ice water bath as well, just to see if its accuracy varies over it's operational range. While the most likely scenario is that is high or low by a few degrees, it could be off in a way that isn't proportional to the temperature.

Thanks for the tip. I'll do: Glass of ice water, boiling water off the burner, and a side-by-side at 155 with my glass thermometer.

I bought it for $3 off meritline and didn't think to calibrate it. tisk tisk.

Are you doing full water volumes, or partial volumes + top off water?

It looks like you are doing top off water post-cooldown. If that's the case, you should really add water, mix well, and STOP adding water when you hit your target OG. You shouldn't be trying to hit any arbitrary water volume, let the hydrometer tell you when you've added enough water. Just be sure you are mixing well throughout to get accurate readings.

You might end up with 4.6-4.8 gallons, but your OG will be correct, so the beer will be as the recipe intended instead of literally watered down!

I'm doing partial volumes + top off water. I'll be sure to try your method from here on out.

I figured the instructions that came with the ingredients would be correct, but then again they are somewhat "generic" instructions from kit to kit.

Does anyone think that a packed grain sack would have any impact on the ability of the fermentable sugars being released?
*Note - I have yet to try to test the accuracy of the thermometer as Schol-R-LEA suggested at this point.

Schol-R-LEA said:

I would test it against an ice water bath as well, just to see if its accuracy varies over it's operational range. While the most likely scenario is that is high or low by a few degrees, it could be off in a way that isn't proportional to the temperature.

Click to expand...

So the thermometer was accurate at ice bath and boiling, but at the 165 mark on my glass thermometer, the digital was reading 170. As the glass thermometer dropped, the digital dropped at the same rate with about a 5 degree difference between the two. This seems strange.

I just did a couple mini mashes from austin, a ipa and a canadian ale, I hit the og right on. The only thing I did differently from you or the instructions was a full 1 gallon of sparge water instead of the recommended 1 qt per 2lb of grain.

Hope that helps

davidg410 said:

The only thing I can think of is possibly my grain bag is too small and its not letting all the fermentables out of the grains when i mash? The bag holds 4.5 lbs of grain and I can tie it closed, but it's a pretty tight squeeze.

Any ideas?

Click to expand...

That's exactly it. The grain must be very loose, so that you can thoroughly stir it and it needs to be wetted throughout and with a consistency like a very runny oatmeal at the thickest.

If you have a tight squeeze, just buy another bag or two and split up the grain so that the grain is very loose in there and easily suspended throughout the water. Or get a huge bag and line the whole pot, and don't tie it at all, just use clothespins to hold it in place.