FG overshoot

[MrJay83]

I've overshot my FG and am wondering if it is because I mashed at too low a temperature? I used Brewfather for my figures (FG 1.013) and was to mash at 67C. My Brewzilla usually has a fair bit of difference between what is on the probe and what I measure from the recirc arm so I generally bump it up a bit (in this case 70C).
I'm hoping it doesn't go much lower because 7.5% might be too much for people I'm trying to convert from Heineken to IPAs

 

[The Baron]

How much did you overshoot by Sg and FG and what yeast did you use?

 

[MrJay83]

I was bang on my OG (1.062). It still hasn't finished yet (currently 1.008). It's Verdant IPA and I'm on day 4 so based on previous use I'm sure there's not much left in it.
Is it a case that a lower mash temp will produce the same amount of sugar but it can be more easily converted?

 

[The Baron]

Yes the lower mash temp will produce more fermentable sugars than a higher mash temp but even so the difference in the FG was only about 5 points which equates to approx just under half a % of ABV
Yeasts do sometimes depending on conditions over or under ferment too so take note of that yeast as it may do the same again under your routine which you can accommodate for next time

 

[MrJay83]

Yes the lower mash temp will produce more fermentable sugars than a higher mash temp but even so the difference in the FG was only about 5 points which equates to approx just under half a % of ABV
Yeasts do sometimes depending on conditions over or under ferment too so take note of that yeast as it may do the same again under your routine which you can accommodate for next time

Thanks. I did read that's what happens but wasn't sure.
I track everything but it's hard to keep up with the variation in temperature between probe and recirc arm. I first used Verdant on the DH Verdant IPA and hit all my numbers.
I think this bit of useful kit will be my next investment.
https://shop.humle.se/en/equipment/...ogue-thermometers/in-line-thermometer-camlock

 

[Jim Brewster]

Attenuation seems rather high yes. Worth remembering that dry hopping can kick off further fermentation. I think it either adds or activates different enzymes, or something along those lines.

Mash temp will be a factor. I'm not sure how the attenuation figures are measured for yeasts but presumably the labs assume 100% fermentability of the wort when calculating so I'm not sure if it's a direct relationship as there will be an upper limit on attenuation, depending on the strain.

 

[MrJay83]

I dry hopped at day 3 (following the DH Verdant IPA recipe which worked well before) and didn't see a spike in fermentation. It just continued on as it was. I've used Verdant four times now (dry hopped each time) and it's always been roughly 80% attenuation.

 

[hoppyscotty]

I think the only lever you have to achieve a target FG is temp control in the mash isn't it? Assuming you have decent fermentation temp control, so on that basis I've always assumed that any deviation from target FG is down to lack of mash temp control.

BZ and similar have the temp probe at the bottom so that is where you're measuring. You're going to get some temp drop as the wort is picked up and percolates through the mash so there is bound to be a difference in temp at he top of the mash and the bottom.

Another issue I've found with my BZ is over shooting temp because of the location of the temp sensor. I've got much better results by running a small overflow down the overflow tube...having some cooler wort mixing with the wort at the bottom has reduced the big temp swings I used to see and now bet much more consistent mash temps through the mash. This impact should be reduced in the new V4 units due to PID control.

 

[buddsy]

Are you measuring with a hydrometer?

buddsy

 

[Agentgonzo]

Floating hydrometers (tilt/ispindel/pill) are notoriously unreliable at measuring FG. Yeast gets stuck randomly to the floating hydrometer, which throws off the angle it floats at and thus the SG reading.
Just use the trend to determine whether the fermentation has finished, then measure with a traditional hydrometer to get your FG.

 

[MrJay83]

I think the only lever you have to achieve a target FG is temp control in the mash isn't it? Assuming you have decent fermentation temp control, so on that basis I've always assumed that any deviation from target FG is down to lack of mash temp control.

BZ and similar have the temp probe at the bottom so that is where you're measuring. You're going to get some temp drop as the wort is picked up and percolates through the mash so there is bound to be a difference in temp at he top of the mash and the bottom.

Another issue I've found with my BZ is over shooting temp because of the location of the temp sensor. I've got much better results by running a small overflow down the overflow tube...having some cooler wort mixing with the wort at the bottom has reduced the big temp swings I used to see and now bet much more consistent mash temps through the mash. This impact should be reduced in the new V4 units due to PID control.

With my BZ there seems to be a large difference between the probe and what is measured coming out of the recirc arm. I've seen a lot of people saying the same and just as many saying there isn't much of a difference.
This brew I tried to put into practice all the things I've learned since I got it and paid a lot of attention to the mash and it's temperature. I even tried putting wort down the overflow pipe when I thought it was raising a bit wildly.
I guess in this instance when I thought I was mashing at 67C I was probably still down around 63C.

 

[MrJay83]

Floating hydrometers (tilt/ispindel/pill) are notoriously unreliable at measuring FG. Yeast gets stuck randomly to the floating hydrometer, which throws off the angle it floats at and thus the SG reading.
Just use the trend to determine whether the fermentation has finished, then measure with a traditional hydrometer to get your FG.

Yeah totally get that. Mine is generally very close at the start and the end but can go a bit wild sometimes in the middle. I've always guessed it's because of sticking yeast as you mentioned.
It's been holding steady for 24 hours now so I might be able to bottle tomorrow night if it stays the same.

 

[buddsy]

Id take a test sample and see what it reads on a Hydrometer.

buddsy

 

[MrJay83]

Just for shits and giggles, I will.

 

[buddsy]

I think it would be worth seeing how that compares to what your electronic gadget is saying.

I note your OG of 1.062 was always going to give you a strong old beer even if you would have hit 1.013 that would still have been almost 6.5%

What ABV were you aiming for?

buddsy

 

[MrJay83]

I was aiming for 6.3% @ 1.013.
So I've taken a trial and it's 1.014! My ispindle is saying 1.008. it's always been a couple of points off but not that much.
Side note... I really do love that Verdant IPA yeast. Every beer I've made with it smells great.

 

[buddsy]

All good then!


buddsy

 

[MrJay83]

It's a strange one because it was almost on the money when I transferred after the boil and for my previous brews. It must need to be recalibrated but to be honest I'm just happy with it to give me an idea where I am with fermentation.

 

[hoppyscotty]

With my BZ there seems to be a large difference between the probe and what is measured coming out of the recirc arm. I've seen a lot of people saying the same and just as many saying there isn't much of a difference.
This brew I tried to put into practice all the things I've learned since I got it and paid a lot of attention to the mash and it's temperature. I even tried putting wort down the overflow pipe when I thought it was raising a bit wildly.
I guess in this instance when I thought I was mashing at 67C I was probably still down around 63C.

Well there is an incorrect assumption that if you run recirculation that the wort that comes out of the arm just goes straight down the tube...in reality it mixes with the cooler wort sitting on top of the grain bed. this will mean the wort running down the overflow will be cooler than the wort at the bottom of the vessel and encourage better mixing and, I think, a more accurate reading and less variation in temp change due to the crude on/off thermostatic control. I've noticed a much better and more stable temperature control since making sure I run some overflow...not alot, just a trickle. I have attached a bazooka filter to the metal tip so I can prevent grain dropping down the overflow tube.

If you can get a reduced temperature gradient over the depth of the grain bed then you're going to get more consistent temperatures and therefore more consistent starch conversion and ultimately closer to your target FG.

 

[Agentgonzo]

It's a strange one because it was almost on the money when I transferred after the boil and for my previous brews. It must need to be recalibrated...

Recalibration won't help.

The iSpindel (when well calibrated) will be almost on (if not actually on) the money each time for the original gravity.

However, that isn't the case with final gravity. Yeast will settle on the hydrometer during fermentation and stick to the sides and bottom. Each fermentation will be different and a different amount of yeast will stick to the bottom each time. And a different amount will stick to the top each time. This will throw off the reading by a random amount each brew, and no amount of recalibration will help you or solve this problem I'm afraid. Sometimes the final gravity will be accurate, sometimes it will read under and sometimes it will read over.

but to be honest I'm just happy with it to give me an idea where I am with fermentation

That's all you can ever get out of floating hydrometers when it comes to final gravity I'm afraid.