Poor attenuation in high gravity beers

You could try to add more O2 after 24-36 hours of pitching. Just because you oxygenate for 3 minutes doesn't necessarily mean you are infusing more O2 then you would be after a minute or so. There is a limit to the O2 infusion. Other then that what attenuation are you wanting? You might just need a higher attenuating yeast strain. By the end of fermentation your yeast are living in a toxic environment.

 

Looks like both your beers are at about 60% attenuation. The Irish ale strain has an attenuation of 70-73%.

 

What was the date on your yeast? I've definitely purchased some older stuff on accident and forgot to account for it in my starter.

 

A single pack of yeast in a 3 L starter seems adequate if the pack was brand new, if not you likely under pitched. I'm on a phone so can't check via calculators I normally use.

For better attenuation, mash lower and longer, oxygenate at 24 hours in addition to before pitching, replace portion of base malt with sugar, or copitch more attenuative neutral strain (e.g. Cali ale) with your strain (white labs sells a WLP001/002 blend if you don't want to buy separate packs).

When you say 100% marris, is this an all grain beer or are you assuming your 100% marris extract is actually 100% base malt? If the latter, that may be a source of under attenuation since you can't control the grist or ferment ability of extract (you can however replace some extract with sugar).

 

Go to your closest local brewery that uses a neutral strain like Cal/Chico, and get a big pitch of fresh harvested yeast off of a ripping fermentation, pitch it on the BW and wait another couple weeks. Maybe even rack it off the Irish Ale slurry onto the Cal/Chico. Them yeasts will be hungry as they were ripped out of a gorging session at the brewery, and will be somewhat acclimated to the alcoholic environment already. Should work to get you closer to 70% attenuation.

 

You could try krausening with a more attenuative yeast like Cali. Get a starter of Cali going (fermenting) and pitch that into your beer.

Alternatively rouse the yeast by shaking carboy or raise the temp its sitting at to try and get a few more points.

Also, has your mash thermometer recently been calibrated? Mash temp could be off. My recent Barleywines have both been mashed at 160F for 40 minutes and fermented with the Fullers strain (wy1968/wlp002) and still finished lower than yours (1.028), which is odd.

 

No zinger intended . . . but you don't know how many yeast cells you pitched. You measure grain, water, & temp, then guess on the yeast. It's quite possible a 3L starter is underpitching. I would use an online calculator and try and determine what's needed and how to make a starter(s) to achieve this. Totally accurate? Nope, but it should get you in the ballpark. Also, be aware that even at 1.040 you are approaching the upper alcohol limit of 1275.

Adding dextrose will only help lower the FG if it is added as a replacement of some grain.

Zainasheff/White recommend in Yeast to hit the wort with additional O2 at the 12-18 hour mark of fermentation on OG's over 1.080. This is after first cell division and helps keep the second round healthy. But I wouldn't add O2 at this point.

I've never done it, but in your spot would probably pitch something like 1056 (that has been started) as suggested by the previous two posters. Again, this will be pushing the ABV limit of the yeast.

 

Even if your activator pack of Thames Valley was 15 weeks old (roughly 37% viable), a 3L starter would have given you enough cells. yeastcalculator.com says you'd need 349 billion cells (roughly 18 million per ml) for 5g of 1.104 OG wort and that (using Kai's stir plate calc's) you'd get 459 billion cells (roughly 24 million per ml). 1 million per ml per degree plato (you made 24.5p) is a general rule of thumb FWIW

I'm curious to know if you pitched that entire 3L starter into the fermenter, or if you decanted it first?

If you decanted it first (after only 36 hours), you most likely poured lots of the yeast down the drain since Thames is a poor flocculating strain. I just brewed a beer (11.25g batch with 1.066 SG) with Thames (activator pack that was 2 months old) and I left my 4L starter on the stir plate stirring for 24 hours, then turned the stir plate off and gave it 3 more days just sitting there at room temperature to ensure it fermented completely and encourage the yeast to flocc more before decanting. I purposely did a 4L starter (overkill) to ensure that, even if I poured some un-flocculated cells down the drain when I decanted, I'd have enough yeast make it into the fermenters. I hit FG in less than 7 days @ 79.3% apparent attenuation using a 148F mash temp, a 68F fermentation temp, and a healthy amount of initial oxygenation.

 

I've twice harvested ... starter-ed ... and re-pitched WLP007 into Old Stock ales stuck in the low 30s (target FG low 20s) with good results; however ... buying fresh yeast would be a boatload easier.

 

There are stir plates . . . and then there are stir plates. My stir plate is hard pressed to meet the Zainsheff criteria on yeastcalculator which is about 40% less than the Troester criteria. Maybe I have a puny motor or a sub-standard stir bar, but I struggle to meet the the lower figures. And no, the growth rate isn't stamped on the stir plate, rather it's learned from experience. As you mentioned, lots of variables on the techniques for finishing, chilling, and decanting the starter that could cause problems.

For the OP: Your description of low attenuation is consistent with underpitching and/or under-oxygenation, coupled with approaching the ABV tolerance limit of the yeast. I can think of another half dozen variables that could give you trouble, but this is where I would put my effort.

For the record: I have low experience brewing above 1.100, so some of my comments are academic only. I graciously welcome input for any brewers who have more experience here.

 

Another variable along those lines is how much heat your particular stirplate generates. If it generates a lot, the heat alone (over enough time) can kill off yeast during the process. I'm using a "Stir Plate 3000" from brewmasterswarehouse.com for my larger starters and have had great results.

NOTE: I no longer crash cool my starters prior to decanting. I'm finding that giving them a longer period of time to complete fermentation at room temperature and flocc naturally before decanting at room temperature produces a healthier fermentation of the main batch vs. stressing the yeast by giving them 1 day on a stir plate, 1 day cold crashing, decanting / warming on brew day and pitching..... That being said, I now make my starters 4-5 days prior to brew day rather than 2 days like I used to....

 

Ironically enough, I tried to finish that high in replicating a historical ale recipe that started out at about 1.100, and finished about 10 points lower at 1.030. Maybe I will attempt it again with this yeast, as the attenuation seems lower than the two different ones I used so far. It's a different problem from yours, but for the record I do not have straight O2 to blow into my wort, and only aerate.

Accordingly, I think yeast strain selection may be more important than O2 or pitch rate (as long as you pitch adequately).

 

Not sure if it was mentioned or not, but using sugar as part of your grain bill would be a good idea as well. It will completely ferment out, where as grain will provide complex unfermentable sugars.

 

Never brewed a beer over about 1085, but there have been several articles on high gravity brewing in BYO over the years and some of these can be found by google. One I specifically recall was about a 20%+ beer. Not sure that you want to go there, but the tips may prove helpful.

https://byo.com/all-grain-brewing/item/51-21-alcohol-all-grain-beer

 

next time start with a 500ml stirplate starter. then crash/decant and step up to 3L.
crash and decant that and you should be good to go.

I dont have oxygen setup but the next morning after brewday I pour back and forth between 2 fermentors for another dose of o2. a homebrew yorkshire square type thing if you will.

 

I did a British barleywine that had an OG of 1.115. Half was fermented with 1028, the other with WLP-022 Essex. FG was 1.029 for 1028, 1.024 for Essex. Yeast nutrients, lots of O2 and 3 gallon starters for both yeasts (starters were kegged, and were nice bitters).