No longer getting full fermentations.

I just watched to all grain using an MLT system. I am hitting great OGs and getting great efficiency with this system. I use filtered water, I aerate the wort well after cooling it quickly, I always double pitch liquid yeast, and I use a fermentation chamber to keep the fermenting beer at great temperatures. With this method when I was doing mini mash I got great FGs but the last two batches of AG have had high FGs especially the last batch which only got down to a 1.021. I also let the wort sit at least two-three days after active signs of fermentation are no longer present. Any feedback on what could be happening, I always wanted a nice session beer but I dont want them all to be sessions.

First off, sometimes 2-3 days after visible signs isn't enough. I've seen at least one beer that was in the 1.020's around the 3 week mark, well after visible signs had ceased, but a week later it had dropped another 5 points.

But if you've just switched to AG, you need to look at things in your process that might lead to less fermentable worts.

- What kind of grain bills are you using? Provide a sample recipe or two, and folks might be able to diagnose things.

- What temperatures are you mashing at - and are you sure you're at the temperatures you think? Is your thermometer calibrated? A swing of just a few degrees can easily explain a few extra points in your FG.

Those are the main things I can think of off the top of my head...

I am using BeerSmith 2 to make my recipes and the software automatically calculates how much fermentables you will have with what you use. It also calculates excatly how much water and at what temperature to mash in, mash out, and sparge at taking into mind the equipment I use. This particular recipe with the high FG I lost when my computer malfunctioned earlier this week. As I recall the total grain bill was around 12 pounds with at least 7-8 pounds of that being two row pale malt and all of the grains where milled and are fully modified. I also do not know if my thermometer is calibrated, I just bought a kitchen thermo on amazon and I have been using that. It has gotten me accurate readings and with all of the methods I use I was hitting really well on the mark for FGs on my mini mash recipes.

But that's tough to go by... In mini-mash, the bulk of your fermentables are still coming from your extract. Even in an all grain mash, you can still hit your OG exactly, but if you mashed too high, you'll still have a large amount of long chain sugars in the wort that your yeast can't break down, which will lead to higher than expected FG.

Are you familiar with how to test/calibrate a thermometer? Make sure to do so before your next brew day - you may find that your thermometer is reading 2 or 3 degrees low. But I'd still like to know what temperatures your recipes are telling you to aim for. The closer to 160 you get, for instance, the higher that FG is going to be.

I'd second checking the thermometer, if you're accidentally mashing 5-10 degrees hot that would easily explain the problem.

I will check the thermometer before brewing next, any suggestions on how to do so? Also, I thought mashing at one temperature would produce the same affect of getting the long and short chained sugars you needed.

Check it in boiling distilled water; it should say 212. Fill a glass with ice and add water. Let it sit a few minutes before checking temp. It should say 32.

If both your numbers are what they should be, your problem is something else. If both your temps are off by the same amount, you'll have to adjust by that amount in the future. If your numbers are off, but not by the same amount, get a new thermometer.

I would check your thermometer and hydrometer to make sure they are calibrated. If they are I would make sure you pitching enough healthy yeast, use yeast nutrients, and oxygenate with pure 02.

Beersmith will tell you if the recipe will produce numbers that will hit certain styles. You can still use too much adjunct grains and get a lot of unfermentable sugars. The software is a tool. You have to use it properly to get good results.

You said you lost your recipe but was it a high gravity brew? If so a FG of 1.021 might have been as good as you will get.

Also, 2-3 days after active fermentation is a very haphazard way of determining FG. You need to take gravity readings over 3 days and have the same numbers. Even then you may have a stalled fermentation and further action would be necessary to finish.

I always ferment for 3-4 weeks and take my readings. This gives the yeast time to finish active fermentation and then time to clean up all the bad byproducts created in primary fermentation.

I agree with checking the calibration of your thermometer as that is a likely source of trouble.

ATXbrew said:

I am using BeerSmith 2 to make my recipes and the software automatically calculates how much fermentables you will have with what you use.

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Actually, no it doesn't. Not really. It doesn't seem to "know" that corn sugar is 100% fermentable while crystal malt is not, and will not adjust the anticipated FG. It just seems to adjust it based on average attenuation of the yeast. I do a better job of estimating FG than Beersmith every time!

Anyway, I'd try mashing 3 degrees cooler than whatever you're mashing at now. I'd also suggest posting a recipe so that we can see where the problem may lie.

kingwood-kid said:

Check it in boiling distilled water; it should say 212. Fill a glass with ice and add water. Let it sit a few minutes before checking temp. It should say 32.

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This is good advice but let me add two amendments:

1) It should say 212*F if you're at sea level. Boiling temperature goes down as your increase in elevation. For instance, water boils at 206.2*F at my elevation.

2) It should be crushed ice with just enough water to cover said ice. That will ensure it's 32 as the H2O is now in a state of equilibrium of changing from liquid to solid state.

ATXbrew said:

I will check the thermometer before brewing next, any suggestions on how to do so? Also, I thought mashing at one temperature would produce the same affect of getting the long and short chained sugars you needed.

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Well, yes. But that temperature will be determined by your desired results. For example, say you have this recipe:

10 pounds two-row
1 pound crystal malt

To get a FG at about 1.008, mash it at 148 degrees. It might even go lower, depending on yeast strain. To get a FG of 1.018 or even higher, mash it at 158. It'll be less fermentable with a much fuller body at the higher mash temp.

Reno_eNVy said:

This is good advice but let me add two amendments:

1) It should say 212*F if you're at sea level. Boiling temperature goes down as your increase in elevation. For instance, water boils at 206.2*F at my elevation.
.

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Yup! My water boils at 206F as well, so this is what I set all of my thermometers to...