Messed up measuring OG of wort going into fermenter - but not sure how

[Avocado_Power]

Hi all, I just brewed a stout recipe with a target OG of 1.060 on a new Spike system, and am not hitting the claimed 80% efficiency, but at a 1.048 for preboil, it's telling me 73% so I can live with that.

My problem is that when I measured the OG of the wort going from the CFC into the fermenter, and I sampled it midstream, it read 1.043.

How it this even possible? Logically it makes no sense. Is something wrong with my method of sampling? Thanks in advance for any pointers!

 

[philly224]

What temp are you taking the measurements at and what are you using to take them?

If you are using a hydrometer and it's above 68 degrees the reading isn't going to be accurate.

 

[dmtaylor]

Likely a simple matter of temperature effects. Readings will seem very low at elevated temperatures. You should take your gravity measurements at 60-70 F for the greatest accuracy.

 

[IslandLizard]

Congrats with your new system!

Aside from taking (hydrometer) readings at or near the instrument's calibrated temps, your low efficiency IS the larger problem.

Once your system is all "dialed in" you would only need to take readings at critical points, such as your first runnings or better yet, at the end of the mash before mashing out to verify it all went fine. Perhaps a few others for your metrics and peace of mind, like your pre-boil gravity and one after chilling. A refractometer (~$20-25) is the fastest way, as they only need one or 2 drops. To prevent evaporation skewing your readings during sampling, cool hot wort samples down a bit (e.g., a cool/cold thick glass). Then again, there's nothing wrong with using a hydrometer and a thick cold glass or swirling the sample in a cold water or small ice bath.

But you should trace the reason for that low mash efficiency. 80% should be about the minimum for 1.060 beers. I'd aim at 85%, especially for larger ($$) batch sizes. Most low efficiencies can be traced to grist that is too coarse, so milling a bit finer may be all that's needed. Other factors are mash temps that are either too low or too high (happens with new systems), malt with low diastatic power, mash tun losses (large deadspace) or inefficient sparging methods, water chemistry, etc.

 

[Avocado_Power]

What temp are you taking the measurements at and what are you using to take them?

If you are using a hydrometer and it's above 68 degrees the reading isn't going to be accurate.

I am not quite sure but if I had to guesstimate I am measuring around mid-80s temp. Sounds like this isn't a good idea. I think given that I always brew in warm ambient temps, I might have to stick the sample in the ref for a few minutes first. I am using a refractometer for everything on the hot side.

 

[Avocado_Power]

I apologize for having issues figuring out this "multi-quote" feature, but dmtaylor, my reply to you and philly224 is largely the same. Thanks for flagging this!

IslandLizard - thanks for the well-wishes. Looks like I shouldn't be satisfied with not hitting 80%. If I were to venture a guess, I would think that it has to do with milling the grains too coarse and inefficient sparging methods. I had been sparging on a 1-bbl system WAY too fast (in 10 mins), so the last brew I increased it to about 20-25 mins. Looks like I need to slow it down even more.

But back to my other point, isn't it actually impossible to have (accurately) measured a preboil gravity that is higher than the postboil gravity of chilled wort going into the fermenter? I mean, boiling concentrates the liquid so the OG must be higher. I suppose this can be chalked up to measuring wort that is too hot for the refractometer's calibrations.

I will be brewing again in about a week and will report back more measurements. THANKS guys
for you all your help.

 

[day_trippr]

Observational experience would favor insufficient homogenization prior to taking the gravity sample vs some outlier cause.
Happens all the time, and the results can go either way - higher than expected or lower...

Cheers!