Hydrometer weirdness

[FedoraDave]

Or yeast weirdness, or something. I'm not sure what to make of this trend, but it's been consistent in pretty much every batch I've made for quite some time now.

I take a gravity reading just before I pitch my yeast. Let's say the OG is 1.058. That means the FG should be in the 1.014 area. But after three week of fermentation, I take a reading, and it's usually about 0.010 lower than the projection, and I get a reading in the neighborhood of 1.004. I'm not complaining, because often my OG is slightly under what my software projects, so I'm getting an ABV that is around what it should be. And the beer tastes fine. I just find it a curious development.

My process differs slightly from batch to batch, depending on the recipe/batch size. For fivers I use the mash tun and do two sparges. For 2.5 batches I do BIAB with one sparge. Some recipes I use liquid yeast, some I use dry yeast. It doesn't seem to matter; my FG is lower than projected.

Odd.

[RickBeer]

With an OG of 1.058, an approximation of FG would be 25% of that, or 1.0145.

However, what yeast are you using? Different yeast have different attenuations.

S-05 says it should be around 81%, or 1.011. Yet people get from low 70s to over 80%.

I've gotten the following from S-05 (same row is same brew at different time):

78.6, 76.8
84.4, 84.9, 87.0
81.4
80.6, 80.2, 87
80.7. 82.7

So, on the low end, an OG of 1.058 would have yielded 1.00754 and on the high end 1.013456. Pretty wide range.

Also keep in mind things like accuracy of hydrometer, temperature reading taken at, and accuracy of reading. I calibrated my hydrometers recently and learned that one was 0.002 lower (I knew one was different, didn't know which one was right). For the last one, is it 1.010 or 1.0105? Or 1.0095? Going from 1.058 to 1.0095 is 83.6% attenuation, going to 1.0105 is 81.9%. OG would vary from 6.35 to 6.22, or for most 6.2 to 6.4.

[MadBrewer]

If it seems to be with every batch, seems like it would be a process thing encourging a more fermentable wort. Getting FG's that low would make for some really dry beers. Are you sure your hydrometer is working correctly? It's rare but that paper scale inside can shift giving you off readings. Are you sure youre thermometer(s) are calibrated and reading mash temps correctly? Mashing lower than you think you are could lead to fermentability changes.

These are just obvious factors, if those are true readings there's something underlying that is pushing the wort to be that fermentable. Especially if you are using different yeasts.

[mashani]

Are you mashing in the 140s? That would be one explanation. (more fermentable wort like MadBrewer mentioned).

Have you used some Bella Saison/French Saison? Even the slightest cross contamination with that stuff will easily cause your beer to ferment out a bunch of extra points every time. At slight levels you might not notice any flavor contribution, it would really only grow enough to really chew stuff up after your primary yeast was puttering out. You'd just notice it as your FG keeps dropping for a bit longer then you'd expect. Or if you weren't paying attention/using a hydrometer, as foamers/bottle bombs, but without any 'off flavor'.

[FedoraDave]

Interesting responses.

I can't really attribute it to hydrometer error. I use the same one for both OG and FG, so if the FG is off because of hydrometer error, wouldn't the OG be off, too? And wouldn't it still be 25% of the OG, even if the OG was off?

As far as mash temps, I usually mash in the mid-150s, unless I'm aiming for a more malty/less alcohol beer, such as one of my amber lagers, and then I mash around 158.

The reading temperature is usually in the mid-60s. That's slightly high, I know, but I'm making beer, not sending a rocket to the moon. And the beer usually ferments in the mid-60s and that's usually the temperature when I take the FG reading. So, again, the numbers may not be "true," but they're true relative to each other, for the most part.

It may be the yeast. For a lot of my recent batches, I've been using either S-05 or Mangrove Jack M10, and they are both pretty aggressive yeasts. A lot of those are pale ales, and I like those yeasts for that style. The liquid yeasts depend on the batch. A Kölsch gets White Labs Kölsch yeast, naturally. My Oktoberfest got White Labs German Lager yeast, etc. Some are fivers and some are 2.5, and I try to make yeast starters for the fivers and especially for the lagers, but the Kölsch was a 2.5 batch, and I didn't make a starter, figuring there were plenty of cells for that size batch.

Probably too many variables to pin it down. Maybe I'll spring for a new hydrometer next time I'm at the LHBS, just to see if it was the equipment.

[BlackDuck]

Maybe I'll spring for a new hydrometer next time I'm at the LHBS, just to see if it was the equipment.

Make sure you get the one that measures to 5 decimal places out!!

[MadBrewer]

Interesting responses.

I can't really attribute it to hydrometer error. I use the same one for both OG and FG, so if the FG is off because of hydrometer error, wouldn't the OG be off, too? And wouldn't it still be 25% of the OG, even if the OG was off?

As far as mash temps, I usually mash in the mid-150s, unless I'm aiming for a more malty/less alcohol beer, such as one of my amber lagers, and then I mash around 158.

The reading temperature is usually in the mid-60s. That's slightly high, I know, but I'm making beer, not sending a rocket to the moon. And the beer usually ferments in the mid-60s and that's usually the temperature when I take the FG reading. So, again, the numbers may not be "true," but they're true relative to each other, for the most part.

It may be the yeast. For a lot of my recent batches, I've been using either S-05 or Mangrove Jack M10, and they are both pretty aggressive yeasts. A lot of those are pale ales, and I like those yeasts for that style. The liquid yeasts depend on the batch. A Kölsch gets White Labs Kölsch yeast, naturally. My Oktoberfest got White Labs German Lager yeast, etc.3 Some are fivers and some are 2.5, and I try to make yeast starters for the fivers and especially for the lagers, but the Kölsch was a 2.5 batch, and I didn't make a starter, figuring there were plenty of cells for that size batch.

Probably too many variables to pin it down. Maybe I'll spring for a new hydrometer next time I'm at the LHBS, just to see if it was the equipment.

Thats all true and like mentioned those are the obvious factors that would contribute and also the first and easiest to cross off. There are other factors such as mash ph mash consistency, oxygen for yeast etc than can also effect fermentability. So who knows.

[FedoraDave]

Maybe I'll spring for a new hydrometer next time I'm at the LHBS, just to see if it was the equipment.

Make sure you get the one that measures to 5 decimal places out!!

What part of "I'm making beer, not sending a rocket to the moon" didn't you understand?

Besides, if I wanted to get that detailed, I'd spring for a refractometer.

[MadBrewer]

LoL a refractometer creates a whole new can of worms.

[Beer-lord]

Refac's are the shiznad!

[Dawg LB Steve]

Refac's are the shiznad!

UH HUH! YEP!

[mashani]

One other possibility I can think of... Do you oxygenate your wort with Pure O2? If you oxygenate it enough you can actually extend your growth phase, making more daughter cells which can end up like an overpitch if you are pitching enough yeast to begin with. That would likely chew some extra points off. This would be pretty impossible to do without the schiznad though.

[FedoraDave]

One other possibility I can think of... Do you oxygenate your wort with Pure O2?

No, I don't do that. For the fivers, I use a nylon wine degasser in my cordless drill. Mixes it up very well. For the 2.5s I chill the wort in the sink, stirring it with a wire whisk. It takes a little longer, but it gets the job done, and the wort is very foamy by the time I transfer to the carboy, which I do via pouring through a funnel, rather than racking with an auto-siphon. So both methods result in a lot of aeration, but not with pure oxygen.

[jimjohson]

I have no ideas why, but I have noticed the same thing with my brews. Even the few I actually hit the OG dead on, finished a little lower than expected. I do not use pure O2 (I pour bucket to bucket). Nor do I use anything but dry yeast(all my LHBS carries), with my "go to(s)" being 04, 05, & 06.

[braukasper]

Dave one thing that has made a difference for me. Is to take the milled grains temp just before mashing, I mill just before brewing. Believe it or not milling may raise your grains temp. A slight variation in grist temp may cause you to have a more fermentable wort then you anticipated.