Four Consecutive Stuck AG Fermentations

[daveylaa]

Hi all any ideas appreciated.

Having brewed 15 AG's with no issues, over the last 2 years. Since Feb 4 of 5 IPA type Ag's have finished fermentation at 1.016 then 1.014 twice (those 3 using SO4) and now at 1.022 (Youngs Ale Yeast- previously faultless). Brew 3 of 5 was fine at 1.012.

All started vigorously, ( i always rehydrate dried yeast) and got to the respective SG within 3 - 5 days. Then with testing on days 6 to day 14, there has been no drop in SG at all. All yeast well in date.

I rouse my yeast, I rinse the steriliser out well, I have always used Brupacks C>R>S, teaspoon of Gypsum in the mash tun and boiler. Having used a half a campden tablet and the above water treatment for all my 30L of mash and sparge water.

The numbers are within a point of or spot on the BREWMATE calculations. They are all IPA's at 1.039 to 1.043 SG pre yeast, so not strong beers!

There are 4 issues I think may be the culperate, 2 are with my method and the first one is: I am using for the first time pre mixed grains for all the 5 brews above!

So could it be something to do with pre mixed pre weighed grains? i.e. old grains?

Or could too much Gypsum or CRS slow the fermentation at the end. As the SG is spot on pre yeast the PH must be ok (I don't test anymore)

Or could it be my temp regulation. I have stated using a brewbelt from Bew 2 to brew 5, temp 18 to 21 with occasional 24's. I even have 2 thermometers, i.e 18 at the base whist 21 at the lid. when 24 I switch off until 21.

Lastly, for each one of these I have added 2 -3 litres of un treated tap water to top up fermenter to 23L.

A lot of data here, cant think of anything else?

Cheers

Dave

[boingy]

Some questions, in no particular order:

1. How have you stored the yeast?
2. Have you checked your hydro accuracy?
3. How do the stuck beers taste?
4. How stable is your mash temperature?

[jimp2003]

What temp are you mashing at? A higher mash temp will give more unfermentable sugars and therefore a higher FG...

[daveylaa]

Cheers for quick replies.

1. How have you stored the yeast? ( in fridge or straight from shop)
2. Have you checked your hydro accuracy? ( sort of! it is 1.000 or 1.001 at room temp with tap water)
3. How do the stuck beers taste? ( nice! drinking no 1 now, did have fruit fly infection before so now know what that tastse like)

4. How stable is your mash temperature? (this I did not really write down as I do put in the mash water a bit hot, 73 to compensate for home made Tun but I mash at (put the lid on) at about 68/9 but no more) then only loose 2 degrees as I use 4 season sleeping bags. I did test the final temp and it was 68 on the last brew.

That sounds like the culperate as un fermentable sugars could account for this isse AND I have only started batch sparging at 74 c. I used to 'drip sparge' so even my sparge water is quite hot. Sounds like something that could relase lots of late non fermentable sugers.

Cheers sounds like a solution. No pun intended.

best wishes Dave

[Rick_UK]

FWIW I had a similar problem with high FG's but I was lazily floating the hydrometer in the FV to get a reading. When I drew off wort from below the surface into a trail jar the reading was where it should have been.

Make sure there's nothing causing a bad reading and your hydrometer is still calibrated correctly.

Rick

[daveylaa]

Cheers

Yes I do sue a clean 'proper' SG trial jar, the Hydrometer reads what brewsmith says is should for the brew and method, so I belive it, so to speak.

Thanks
Dave

[far9410]

Keeping the correct ferment temp constant is important

[daveylaa]

Cheers, I do try keeping at 21 but is is difficult. I am probably going to invest in a thermostatic heating pad. Don't like fish tank heaters. Just cant leave electricity in 'water' whilst I am away for days at a time.

NB nver have problems with Lager AG and Munich Yeast as my unheated lobby is around 9-11c Sep - March.

So temp may also be a factor.

[daveylaa]

NB previous 15 brews mashed in a Brupakcs Made mash tun, probably at right temp. Since returing to brewing I am using a mad home made tun, hence slightly higher strike temps. which may explain the possibility of non fermentable sugers.

[gregorach]

It's almost certainly down to the change in mashing equipment / temperature then. Small changes there can make a big difference.

[daveylaa]

Cheers Dunc

it's something that sounds like the most credible culprate.

Dave

[boingy]

And FG is not everything. You said the one you sampled tastes nice. So it's not so bad!
Although the 1.022 one may be a different story....

[daveylaa]

Good point, even the 1.022 tastes nice too!
Just careful due to diabetes, (type 2 so not so critical), stopped brewing fora year, got blood sugars down to normal, will probably give the 1.022 away.. 1.014 is fine I hope.. time will tell. Cheers Dave

[Kev888]

Hi, 68/9c is definately a warm mash which will result in a higher FG - the 1.016 and lower FGs could be due largely to that. If so, whilst its not perhaps common to mash so warm for this style of brew its just a matter of your own preference rather than a problem as such. The 1.022 however sounds like it may have had an actual problem, it seems high for a modest OG, even with a fairly warm mash.

I find that its definately worth monitoring the mash temperature, as it has a very notable effect. The range I personally use is between about 62c for dry beers up to about 68c for sweet malty beers, and I use around 64c for a strongish IPA with us-05 yeast. The temperature can also appear to rise initially as the heat evens out, especially if the grain wasn't mixed in thoroughly, so its possible the mash may have become warmer than your initial temperature reading suggests (and its worth checking your thermometer beforehand too, as some are pretty inaccurate).

If you're mashing so warm because the temperature falls initially, its possible you may need to warm the MT through a bit more first. Ideally your mash liquor will be 'reasonably' steady at the correct strike temperature for the grain before you mash in, rather than having to use a higher temperature of mash to compensate. Some people pre-heat the MT by dumping in a kettle full of boiling water and drain that out after several mins, I instead fill it with hotter liquor and let it warm through for say a good quarter of an hour before progressing. From experience with this particular MT I know how much it cools the liquor so I can use a temperature that ends up at about the right strike temperature once its thoroughly warmed the MT up; when the MT was new though it was much more hit and miss, and I had to do a lot of pratting about adjusting it before adding the grain.

Cheers
Kev

[daveylaa]

Thanks Kev
thats a very detailed response, i only ever aimed at 68 for all brews. I will have a more detailed mess about with my temp regulation. never paid much attention to this aspect. it sort of all makes a bit more sense now. Cheers Dave