SG readings all over the place 1.030 on refractometer and 1.070 on hydrometer

[Froyd]

I designed a simple recipe with Beersmith. Maris Otter LME and approx 10% rye mini mashed/steeped at 155F. Calculated SG was supposed to be 1.049. However, my refractometer reading was way lower 1.035 during a spot check, before I even got to the fully diluted volume in the fermenter. Suspicious of having missed the mark by such a wide margin, I took a hydrometer reading which was way too high at the other end of the spectrum.

Not sure what to do, I decided to trust the volumes in the recipe, and diluted to my target of 4.5 gallons, which should have yielded the 1.049 SG and instead gave me 1.030 on the refractometer and 1.070 on the hydrometer. Temp of cooled wort was 70F, close enough to 68F that it could not justify the big delta between the readings.

I took a reading of distilled water in the refractometer, and confirmed it was calibrated at 0. Did the same with plain water in the hydrometer test jar and got a 1.000 reading. The instruments seemed to be calibrated just fine.

I retook a refractometer reading and used the Brix scale in case the conversion was not accurate and confirmed that the reading was still around 1.030.

(...in the meantime, my rehydrated yeast was looking kinda tired, having waited more than 45 minutes to be pitched while i took multiple reading and checked calibrations. Hopefully, the viability was still high enough and the fermentor seems to be bubbling OK this morning.)

Back to those darned measuring instruments: this morning I mixed up some DME and water to get an estimated 1.042 mixture. I also bought a high precision hydrometer that confirmed the density to be 1.041. The old hydometer, the one that gave me the 1.070 reading, was also reading 1.041, and the refractometer came close at 1.040. All the readings were in agreement!

I have no clue of what could have possibly gone wrong on brew day to get me such different readings. Any ideas?

 

[IslandLizard]

Once alcohol is present you need to use a correction formula to estimate the actual specific gravity (SG) using a refractometer. Alcohol changes the refractive index of the solution.

Refractometer Calculator - Sean Terrill

Or use a hydrometer, which may be more accurate, anyway, for this.
Or do both and correlate the results. It can be an eye opener.

 

[bracconiere]

i'd say "maybe" the LME wasn't stirred in evenly? best guess....but if was boiled, don't know.....weird

 

[IslandLizard]

Just reread your OP, it appears your measurements are all before fermentation.
Direct refractometer readings are correct then, no need for the alcohol correction formula (there's no alcohol yet).

But... beware of transferring one drop of hot wort to the refractometer prism. Some of it can evaporate during that transfer, badly skewing your gravity reading. I've been fooled a few times by that. There can be some compounding errors too.

Diluting partial boils are always suspect to incomplete mixing and thus misleading and non-repeatable readings. Stratification is real!

With extract brews, you can simply rely on gravity points from your extract (plus points from your mini mash and steep). As long as you don't spill any or leave a lot behind in the kettle, there are no points lost. xx points on the counter = xx points in the kettle = xx points in fermenter. Only the volume changes (after dilution) and with that your SG.

Was that Rye malt you mini mashed?
How did that go? Must have been some interesting gooey gluey event.

 

[Froyd]

Once alcohol is present you need to use a correction formula to estimate the actual specific gravity (SG) using a refractometer. Alcohol changes the refractive index of the solution.

Refractometer Calculator - Sean Terrill

Or use a hydrometer, which may be more accurate, anyway, for this.
Or do both and correlate the results. It can be an eye opener.

But there was no alcohol present at all. Just cooled wort, no yeast added yet. I thought that was clear in the write up, but maybe the SG/OG is causing confusion. I meant gravity of the unfermented wort, calculated to be around 1.049 by beersmith

 

[Froyd]

But there was no alcohol present at all. Just cooled wort, no yeast added yet. I thought that was clear in the write up, but maybe the SG/OG is causing confusion. I meant gravity of the unfermented wort, calculated to be around 1.049 by beersmith

Duh. Just read your second comment... Sorry, I'm answering from my phone and did not review the whole thread.

 

[IslandLizard]

Duh. Just read your second comment... Sorry, I'm answering from my phone and did not review the whole thread.

No, the "Duh" is on me, I read your OP wrong.

 

[Froyd]

But... beware of transferring one drop of hot wort to the refractometer prism. Some of it can evaporate during that transfer, badly skewing your gravity reading. I've been fooled a few times by that. There can be some compounding errors too.

Diluting partial boils are always suspect to incomplete mixing and thus misleading and non-repeatable readings. Stratification is real!

I think the stratification idea has the most merit. I did pout the cooled kettle content into the receiving fermenter from a couple of feet, splashing quite a bit in the water below, but maybe it was not mixed enough. Temp and evaporation did not apply at my measuring temperature (70F)

Was that Rye malt you mini mashed?
How did that go? Must have been some interesting gooey gluey event.

Yes, Rye malt. Small amount, 0.7lbs. My systeme is to steep it in a small pot while my larger kettle comes to a boil. I steep the grains loose (no muslin bag) and then drain into the kettle through a colander. The rye was double milled and I used only 0.5 gallons of water. I ended up with porridge, but the liquid seem to drain out well, and my dog is going to enjoy the dog treats from the grains.

 

[Nate R]

I designed a simple recipe with Beersmith. Maris Otter LME and approx 10% rye mini mashed/steeped at 155F. Calculated SG was supposed to be 1.049. However, my refractometer reading was way lower 1.035 during a spot check, before I even got to the fully diluted volume in the fermenter. Suspicious of having missed the mark by such a wide margin, I took a hydrometer reading which was way too high at the other end of the spectrum.

Not sure what to do, I decided to trust the volumes in the recipe, and diluted to my target of 4.5 gallons, which should have yielded the 1.049 SG and instead gave me 1.030 on the refractometer and 1.070 on the hydrometer. Temp of cooled wort was 70F, close enough to 68F that it could not justify the big delta between the readings.

I took a reading of distilled water in the refractometer, and confirmed it was calibrated at 0. Did the same with plain water in the hydrometer test jar and got a 1.000 reading. The instruments seemed to be calibrated just fine.

I retook a refractometer reading and used the Brix scale in case the conversion was not accurate and confirmed that the reading was still around 1.030.

(...in the meantime, my rehydrated yeast was looking kinda tired, having waited more than 45 minutes to be pitched while i took multiple reading and checked calibrations. Hopefully, the viability was still high enough and the fermentor seems to be bubbling OK this morning.)

Back to those darned measuring instruments: this morning I mixed up some DME and water to get an estimated 1.042 mixture. I also bought a high precision hydrometer that confirmed the density to be 1.041. The old hydometer, the one that gave me the 1.070 reading, was also reading 1.041, and the refractometer came close at 1.040. All the readings were in agreement!

I have no clue of what could have possibly gone wrong on brew day to get me such different readings. Any ideas?

Fwiw, i have a fairly cheap amazon special $20 refractometer. That said, it has always matched my hydrometer spot on...
But...
These thinga are finicky. I suggest taking a few readings each time (example- take a sample, stir ((if you can safely do)) and sample again.)
I get 200 pieces plastic pipettes at a time ($9 on amazon) so i can sample a lot.
Occasionally i will get different readings- say 1.058 one time and 1.060 another.
I then average them (so 1.059 in the example above).
Keep written records of all! Look for trends.

Imo, the much smaller sample size of the refractometer outweighs the potential to be off in precision.

Some day i will splurge for an Easy dens or a Hannah, but would rather spend that money on other things first (like sexy hops or brew gear)

 

[RPh_Guy]

Definitely stratification. Knew as soon as I read your first paragraph. No other explanation makes sense.

 

[IslandLizard]

Yes, Rye malt. Small amount, 0.7lbs. My systeme is to steep it in a small pot...

Small pot is good for small mashes. You can stick it in a pre-warmed but turned off oven to keep temps better. Please note, there is a small but significant difference between steeping and mashing. The former dissolves sugars and flavor compounds, the latter also does diastatic conversion of starches into (fermentable) sugars, and takes about an hour. Look up the differences between the 2 processes. It ain't a mini mash if it isn't "mashed."

Some grains (either malted or not), such as wheat and rye become very viscous when hydrated.
Including some extra (milled) Barley malt, and/or 5% rice hulls can help keeping it more fluid. So does a combined protein/beta-glucanase rest at 131F for 10' before heating up to the saccharification rest (147-160F) and/or stirring well and often during lautering.