Consistent high FG

[pirateagenda]

I have been struggling with having consistently higher FG's than what beersmith is suggesting I have. Starting to annoy me a bit, especially leading into summer because i'd like to do some dry crisp swillers. Some of my recent brews:

- DSGA with US05- est FG 1.010 Actual FG 1.014
- 10 Minute IPA (US05 on yeast cake) - Est FG 1.014 Actual FG 1.017
- Pacific Ale (US05) - Est FG 1.009 Actual 1.012
- Rice Lager (s-23 built up to beersmith cells in 2 stage, 2.5L starter) - Est 1.009, Actual 1.012
- Coopers (recultured coopers yeast built up to 2.5L starter in 3 steps) - Est 1.008, currently 1.013 after 1 week primary

The only one I have gone lower recently is an IIPA with a decent dose of sugar in the boil.

I have cross checked with hydrometer and refractometer and both register the same SG, and both register 1.000 with tap water.

My process:
- Double batch BIAB, full volume mash, 100L aluminium pot with nasa burner
- Mash temps between 62-66 depending on brew
- thermometer measures mash from top of pot (ie no thermowells) (thermometer reads the same as 2 digital ones i have so I assume all 3 are correct)
- mash at temp for 60-90 mins, stir 3 times during this time. noramally lose 1-2C over mash period
- water has additions and PH is always between 5.2 and 5.5
- Heat mash to 78 with the bag still in, stirring constantly (about 10 minutes)
- rest for 5 mins at 78
- remove bag and boil
- wort chilled with immersion chiller immediately following boil
- yeast normally pitched the next morning
- wort oxygenated with bunnings oxygen prior to pitching yeast
- yeast either hydrated if dry, starter built if required or pitched onto yeast cake.
- Ferment under pressure, limited to 15psi for first few days, then allowed to rise to 20-30 to finish.
- Normally ferment around a controlled 18-19C for us-05 then allow to rise to 20C for 1 day after FG stable, the s-23 i fermented at 13C until 1.020 then ramped to 19C for 1 week

Any suggestions as to what my problem is?

The ONLY thing i can think of is that my thermometer is only reading the top of the wort and maybe the bottom is hotter and i am mashing higher than I think, although I would have thought the stirring would fix that. Or that all 3 of my thermometers are on the piss and reading low.

 

[Rocker1986]

Could be a temp issue. I measure mine the same way but it's only a 40L urn doing single batches. I always hit the predicted FG or get within a point or two if it.

Is the mash profile selected correctly for each batch? It sounds a silly question but sometimes it's the simple things.

 

[pirateagenda]

Could be a temp issue. I measure mine the same way but it's only a 40L urn doing single batches. I always hit the predicted FG or get within a point or two if it.

Is the mash profile selected correctly for each batch? It sounds a silly question but sometimes it's the simple things.

Yep, all of them have been mashed at the right temp according to beersmith.

1-2 points wouldn't bother me, but when it's consistently 3-4 points its slightly irritating!

 

[Danscraftbeer]

That's so similar to what I do only its esky mashed not BIAB. I consistently hit spot on or get lower FG than beersmith estimates. The only thing I can think is in line with your thoughts. The thermometer reading wrong or the heat not distibuted evenly for the reading etc. Another reason I don't do BIAB, restricted for stirring etc..
3 thermometers all reading low seems unlikely.

 

[Tony121]

Thermometers reading the same at ambient temp or mash temp?

 

[pirateagenda]

Thermometers reading the same at ambient temp or mash temp?

All reading the same in 22c tap water

 

[Yuz]

So far I've been getting consistent high FG with my dark lagers, using both S-189 and W-34 (15g pack, hydrated)
Using Ian's worksheet, predicted FG is typically 1.009, but mine ends up being around 1.015 +/- one point.
OG is from 1.032 and not over 1.040 in standard 23L batches. Worksheet's calculated OG is confirmed by refractometer - every time it's spot on.
Could the high FG be because of the dark style itself? I steep CaraAroma as well.

 

[Rocker1986]

What are your recipes to get an OG that low?

You need to correct for alcohol if using a refractometer post fermentation as well.

 

[Tony121]

All reading the same in 22c tap water

Test them all in ice water and also boiling water, you may be surprised. Then again you may not but it takes another thing out of the equation.

 

[Yuz]

What are your recipes to get an OG that low?

You need to correct for alcohol if using a refractometer post fermentation as well.

Typically I'd do a 1.7kg can (Coopers or Black Rock) + 1kg light DME for fermentables, + 300g grains steeped. This gets 1.040 OG, both in calculations and as measured. I aim for a low alc content (around 3%), so the low OG is intentional.

I'm guessing the bottle FG (after conditioning / secondary in the bottle) should bring it further down but my batches are bottled @ 1.015 as it doesn't drop any lower - after two weeks primary (in either Fermentasaurus or Cooper's traditional bucket). Doesn't really worry me but this post got me curious

Edit - I do calibrate the refractometer and am aware of offset readings with alc.

 

[Rocker1986]

It won't drop any lower in the bottles either, or at least it shouldn't. Infection or wild yeast would be the main cause of the FG dropping further in the bottles. The priming sugar will obviously increase the SG slightly but once it ferments out it will just go back to the original FG. In other words, if it's bottled at 1.015, it will remain at 1.015 after bottle conditioning.

In any case, you should be getting FGs lower than 1.015 with those ingredients in 23 litres. I wouldn't quite go as low as 1.009 although that would depend on the yeast strain as well (lager yeast generally ferment out more than ale yeast), but it should be somewhere around 1.010-12 at a guess.

 

[pirateagenda]

Test them all in ice water and also boiling water, you may be surprised. Then again you may not but it takes another thing out of the equation.

Just put 2 of them in hot tap water with a 1C difference, at 60 with a 1C difference and at 80 were the same again. So the one i use is reading 1C low which might account for a point or two.

Was just playing with the mash profiles in beer smith and adjusting the mash temp is bringing the FG's closer to mine, so that has me leaning towards my mash is higher than I think. Maybe both of my thermometers are slightly low, or mash is cooler nearer to the surface.

Will try and mash 2-3C lower than planned next brew and see if that fixes it. I can't think of anything else it could be.

 

[technobabble66]

Are you stirring the mash thoroughly after mashing in? (i.e.: not just initially, but for a solid 5-6mins after it looks like it fully mashed in - so maybe up to 10mins in total?))
This might be an issue for 2 reasons: 1) uniform heat distribution; & 2) Dough-balls.

If dough balls are present, they should be breaking up during the ramp to 78°C where you say you're stirring, so the high temps at that point when the starches are exposed to the enzymes in the liquid could result in extra unfermentables.
Similarly, non-uniform heat distribution throughout the mash could result in some areas being high in temp, some being lower. Again, the higher temp sections would result in more unfermentables.
It seems like you've already thought about this stuff, but just putting my 2c in

Basically, i'd be looking at something messing with mash temp. Seems most likely to be what would cause higher FG - from the additional unfermentables generated.
The other option could be lack of yeast health, however your process looks like this shouldn't be an issue. Minor point is i'd ramp to the higher finishing fermentation temp (e.g.: 20°C) while there's still 4-5 points to go; which would be ~1.020 for you (to be safe).

 

[laxation]

Are you stirring the mash thoroughly after mashing in? (i.e.: not just initially, but for a solid 5-6mins after it looks like it fully mashed in - so maybe up to 10mins in total?)

How much heat do you reckon you lose stirring for that long? (for biab in an urn)

I've been getting similar problems the last few brews so watching this thread closely!

 

[Tony121]

Just put 2 of them in hot tap water with a 1C difference, at 60 with a 1C difference and at 80 were the same again. So the one i use is reading 1C low which might account for a point or two.

Was just playing with the mash profiles in beer smith and adjusting the mash temp is bringing the FG's closer to mine, so that has me leaning towards my mash is higher than I think. Maybe both of my thermometers are slightly low, or mash is cooler nearer to the surface.

Will try and mash 2-3C lower than planned next brew and see if that fixes it. I can't think of anything else it could be.

Not a big difference, though still a factor.

I'm with Techno, mash temps is where I'd be concentrating.

 

[Jack of all biers]

Test them all in ice water and also boiling water, you may be surprised. Then again you may not but it takes another thing out of the equation.

You really need to do this to calibrate your thermometers. They may be out by 2-3 C at 100C boiling water, but reading normal at 0C or 20C. Your test at circa 60C and circa 80C shows that some are different from the others, but how do you know how much the ones you are comparing against are out by? The only way is to calibrate them as Tony121 described above. If they are reading correct at both those temps then you can be fairly confident that at 66C you are close enough on the money. 2-3C is all you need to be out by to be those 3-4 SG points out that you are describing.

 

[dr K]

OP, PirateAgender
So far as I can see, and that may not be that far...you have given your finishing gravities (as well as the est FG) but not your your starting.
You also mention the use of sugar.
A starting gravity finishing gravity input will give you your apparent attenuation which you can comapre against the manufacturers attenuation specs for the yeast you use.
A thin mash (say >6:1 L:G) may create a less fermentable wort
so many reasons not enough SG

K

 

[shacked]

This might be way off but have you tried not fermenting under pressure? I know some of the Saison strains don’t perform well under pressure and tend to stall out even with the “pressure” of an airlock. Maybe this is impacting your yeast? As I said, this might be way off but perhaps another variable to test.

 

[fletcher]

with biab I'm assuming it's a temp issue. I experienced a similar thing when I biab'd except had the opposite where my FG was always 4 or more below. I think it was the inconsistency in temperature throughout my mash which was causing it.

also, how much specialty malt are in your recipes? what percentages?

 

[pirateagenda]

@dr K - beersmith takes into account the OG and attenuation of the selected yeast and ingredients.

@shacked - that could be an issue, I will keep the pressure under 15 all the way through next batch to see what happens

@fletcher - usually around the 5% or under mark - depending on what i'm brewing. but Beersmith should take that into consideration anyway when estimating FG.

Thanks all so far - Looking like uneven mash temps and a slightly out of calibration thermometer are the most likely culprits.