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View Full Version : Hydrometers, F.G.s, and Stuck Fermentations



masterhaleco
01-31-2010, 01:42 PM
Ok, so I thought I was doing good but now I'm concerned or perhaps just overthinking. Let me start by saying that I'm a beer brewer and started this batch of mead thinking it would go down similarly.

My recipe was just:
15 lbs of honey
5 tsp fermax yeast nutrient
juice of one squeezed red grapefruit

Boiled for a few minutes to pasteurize then cooled and split into two carboys and topped off to just under 3 gallons each. The original gravities were 1.093 and 1.099 (I thought they'd be the same, but I must have not divided the boiled must evenly and topped one off with water more than the other or something). I figured I'd try two different yeast strains to do a bit of head to head comparison. So, I rehydrated and pitched red star champagne yeast in one, and lalvin D47 in the other. Thing is, I got the yeasts mixed up during the rehydration and don't know which yeast went in which carboy. Fermentation was quite active for a while and within a month, both meads stopped bubbling in the airlocks and have cleared to a beautiful golden hue. They've sat for another month since and the gravities have stayed steady at 1.009 and 1.004 respectively.

I figured they were ready to be bottled and since I want them to sparkle I won't be stabilizing them, but after reading a bunch of threads, I'm now afraid of overcarbonation in the bottles. The only mead recipes I'd really read were in the back of my joy of homebrewing book by Papazian. In his recipes he says F.G should be between 1.015 and 1.025 and to bottle (and add more sugar for bottle conditioning) at that high a gravity. I thought I was in great shape with my respective gravities, but now I'm reading that FG should be 1.000 or less and that my gravities run the serious risk of turning into bottle bombs.

What I'm getting at is this. If I'm not mistaken, hydrometer readings are not actually readings of the sugar content in the mead, it only tells you the density of the liquid, but that density could come from anything that's in there. Just from looking at the color alone you can tell there's more in there then water and sugar (now alcohol) or it would be clear. The honey I started with was a dark wildflower, and before reading the threads on here about bottle bombs I just assumed that whatever was in the honey that made it dark when it was honey was still in the mead and contributing to the added density showing up on the hydrometer now. Is this assumption wrong? If I was treating this as a beer I would have bottled it as soon as it cleared and the gravity readings stopped dropping (weeks ago). I bottle beers with gravity readings between 1.010 and 1.025 and haven't had any problems (knock knock). I know that mead fermentations are more prone to sticking, but how do I know if it's done or just stuck? Any thoughts or links on the subject are appreciated.

AToE
01-31-2010, 02:10 PM
Beer is different as I understand it, and never really ferments down to 1.000 because it contains a lot of sugars that yeast can't ferment, whereas mead contains completely fermentable sugars.

If you're at 1.010 or 1.015 it could be stuck or done, but either way, it will not carbonate by adding more sugar - if the yeast are unable to finish what they already had they will not be able to ferment what you add in before bottling (unless they wake up and restart due to temp or some other factor, in which case you are now in trouble, because there is nothing to guarantee that they only eat what you added, they could just keep on chewing on the old remaining sugar too, and then BOOM).

So 1.010 or 1.015 might be as dry as it can get for a beer, making priming both safe and effective, but mead needs to be down to 1.000 or lower (totally dry would actually be somewhere closer to 0.990). Any other material in the liquid (colour etc, like you mentioned) should not have a significant effect on SG as far as I know.

Hope that helps.

Dan McFeeley
01-31-2010, 02:46 PM
It's very possible that your meads have finished out and are ready for sparkling. I'd suggest doing a forum search for questions on sparkling meads, or browse through the recipes section to see if there are any sparking mead recipes. That should give you a clearer idea of where your meads stand with the gravities they're at.

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masterhaleco
01-31-2010, 03:31 PM
"whereas mead contains completely fermentable sugars."

See this completely fermentable sugar thing is where I'm confused. When I was buying the yeasts from the brew store the guy there was helping me. I'd made a batch of mead once before using the red star yeast, but I wanted to try something new and he suggested the D47 which he said would not ferment as dryly. He said it would be less dry not because of a lower alcohol tolerence or anything like that, but because not all sugars are the same and that the D47 yeast would be unable to breakdown some of the sugars. After seeing the hydrometer readings, it looked like he was right: one was higher than the other (and actually the one with the lower starting gravity has the higher SG currently). When I search for threads on sparkling, the general consensus is that it's unsafe to bottle condition anything not down to 1.000, but like I said the recipe in a highly reputable (though beer focused) book says FGs in the range of 1.015 to 1.025 and are safe for bottle conditioning. So are these nay-sayers just overly cautious? Or maybe they stick with still meads and are giving advice based on theory and not experience?

Every instinct I have from beer making says that they're done. Instinct says that 1.000 readings happen more in theory than in practice, but I certainly don't want to bottle prematurely and risk bottle bombing the people I give them to. That said, I would also like my carboys back for more brewing.

So I guess my question to those who have brewed a lot more mead than I is, when using these yeast strains what is a reasonable FG for the driest possible mead? Do you actually, in practice not theory, get your FGs down to 1.000 or below? Is the idea of different yeast strains unable to ferment some of the sugars reasonable or are all sugars in honey fermentable by all brewing yeasts?

Finally, I was thinking of adding a small amount of additional must to the carboys. The thinking is if the yeast is done fermenting (not stuck), it will ferment this additional must and return to the current readings. If the fermentation is stuck, then the yeast won't be able to ferment this addtional must either. Is this a good idea?

AToE
01-31-2010, 03:47 PM
I'm not nearly experienced as many of the other people here, but I can say that 1.000 or even lower happens all the time in practice, actually ALL of my meads that I didn't screw up and have a stalled fermentation have finished at between 0.990 and 1.000 (roughly 17 or 18 batches in that range).

That said, Dan McFeeley is a very experienced mead maker and he's saying that you may be able to safely carbonate a mead in the 1.010 1.015 range. He knows a million times more than I do, but that said, I've seen other people with comparable experience to him say the opposite, and to NEVER ever attempt sparkling with a mead that is still sweet.


What I would recommend is to NOT listen to me, I'm a newb and am largly just repeating what I have heard and what I understand. Wait for more of the mead mentors to chime in, and base your actions on what they say. I wouldn't go by that book either, the one thing I do know is that beer is very different from wine and mead as far as non-fermentable sugars are concerned.

As I said though, I'm not a good source, wait for more advice. Whatever the mead mentors tell you will be more accurate than a book aimed at beer. These guys know their stuff!:)

Medsen Fey
01-31-2010, 06:53 PM
You've asked some big questions here, but lets take a look at where you are. You used D47 with alcohol tolerance of 14% (or higher at times) and Red Star (Pasteur?) Champagne with alcohol tolerance of 15%. Both batches stopped with residual sugar and the temp has been kept cool low (low 60s right?)

Batch 1
SG 1.093
FG 1.009
ABV 11-11.5%

Batch 2
SG 1.099
FG 1.004
ABV 12.5-13% ABV

Honey is a complex mix with around 17% water, and lots of sugar. If you look at wikipedia the composition of honey is as follows:
Fructose: 38.2%
Glucose: 31.3%
Sucrose: 1.3%
Maltose: 7.1%
Water: 17.2%
Higher sugars: 1.5%
Ash: 0.2%
Other/undetermined: 3.2%

If you assume all the higher sugars and other (and ash) are non-fermentable then of the solids (non water part of honey) the non-fermentable stuff would be approximately 5.9% (granted there is wide variability). So in a must with a gravity of 1.099 you'd expect just a bit less than 6 gravity points worth of non-fermentable gravity. So clearly a gravity of 1.009 would be expected to have residual sugar. This is not even taking into account the effect of alcohol

Alcohol has a gravity of 0.787. A pure solution of ethanol and water at 12.5% would have a gravity of about 0.973. When you add in all the unfermentable stuff, maybe the gravity gets to 0.980, and the yeast do produce some things like glycerol and organic acids and such so that for a standard strength mead, the expected gravity of a full dry batch would be close to 0.990, and it is common to see dry meads with gravities below 1.000.

If you want to see how much sugar you have left, you can get clinitest tablets (like diabetics use) and measure the sugar. I think they only go up to 1 or 2%, so you're probably going to have to dilute your sample to get it into that range because you've got more than that left in your batch.

The homebrew shop fellow is misinformed when he talks about the relative sugar consumption of the yeast. The limiting factor is their alcohol tolerance and there really aren't any sugars that other sacharromyces strains will consume that D47 won't. Some, such as the Bayanus strains may be able to consume fructose more easily, but essentially they can all consume all the fermentable sugars until they reach their tolerance (and if they are well nourished and managed, they may exceed the usual tolerance).

There are a lot of factors that may keep yeast from chewing up all the sugar available. Low pH is a big one. Undernourishment and lack of aeration (did you aerate these batches?), accumulation of inhibitors (short chain fatty acids), bacterial contamination, temperature extremes, and so forth can all factor in.

All of this is fine theory to cogitate on, but what you really want to know is will this batch ferment safely if you add more honey, right? The easy way is to test it. Take some and fill a 1-liter PET plastic soda bottle along with the amount of honey to get the desired level of carbonation. Take the gravity reading, then put the lid on and seal it up.

The aeration that it gets along with the honey addition may help reactivate the yeast even if they were stalled. If it is kept in a warmer spot that may also rev up the yeast. If it firms up, then you know the yeast are able to chew up more sugar. Let them finish and then open it to check that the level of carbonation is to your liking, and then degas and measure the gravity of a sample. If it fermented more than the extra gravity points you added, then you know you have to be very careful to avoid bottle bombs.

I hope all this rambling makes some sense

Medsen

dr9
01-31-2010, 10:11 PM
If the taste test is good, then bottle it like you planned but crown cap a few beer bottles worth. Every 2 days, open a beer bottle. When it's carbonated to your desired level, cold crash the rest.

That's what they say on the Midwest Brew Supply DVD. I don't know if it's good advice. It's just what I heard.

masterhaleco
01-31-2010, 10:43 PM
Yes, the room it's in stays in the 60-65 deg range and will be til spring. I haven't actually taken temperature readings from the mead itself but I assume since it's cleared and fermentation seems to have stopped that it's temp matches at this point. I did aerate, but only when I first pitched the yeast. After reading some threads it seems I should have been doing it regularly for the first 1/3 of sugar fermentation. I picked up some pH test strips so I could test the acidity, but now I don't think they'll work because they cover the full spectrum range and only have an accuracy +/-1.0 which now seems like a too much for what I'd be looking for.

Thanks for clearing up the issue about the sugars. I was a little skeptical myself when I was told that, but then I figured maybe individual sugars are more complex and variable on the molecular level than I thought, and if so why wouldn't some yeasts be more tolerant then others. What do I know?

But after spending the better part of this weekend reading both threads here and materials elsewhere, I think I am starting to wrap my head around the big picture, the whole theory of mead making. I can see now how most of what I've known up til now was just beer brewers' takes on how to adapt beer brewing to mead making. And while I did manage to pull off a couple a sparkling meads in the past (it was a few years ago now, and I just drank the last bottle a couple months ago - dry, sparkly, smooth, though not much flavor), I really may have just gotten lucky. It felt like everything I read and just took me back another step, but now I see, I must humble myself and truly start from the beginning.

Thanks for the thoughtful responses.

Thanks for the thoughtful responses.

wildoates
01-31-2010, 11:41 PM
My son gets on my case all the time for doing things with mead that you're not supposed to do with beer. He's convinced that someday it'll go wrong on me!

It really is a different mindset, which he's beginning to realize (as I haven't had any disasters yet), so do read as much as you can to get your head wrapped around it. And enjoy!

Dan McFeeley
02-01-2010, 12:14 PM
I think what you are asking is how the final gravity reading is going to affect the finished product, sweetness or dryness of the mead after it's carbonated, and safety risks. To really get a handle on this you'll need to learn some things about how much pressure a bottle can withstand (use either beer bottles or champagne bottles), and how much pressure your priming sugar or honey will generate. Looking at recipes can give you some idea, particularly yeast strain used and finishing gravity before priming.

Try this link for some good info:

http://www.gotmead.com/forum/showthread.php?t=11327

A forum search with the key words atmosphere and Oskaar will get you even more good info.

A few links to short and simple guides:

http://www.ehow.com/how_1615_make-apple-mascarpone.html

http://www.letsdowine.com/howtomaspwi.html

http://www.winemakermag.com/stories/kit/article/indices/25-kit-winemaking/480-making-sparkling-wine-from-kits-wine-kits


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