View Full Version : Gravity?

05-23-2004, 10:41 PM
Great job Viking, Vicky chose the right man for the job.

One thing I've always been confused about was gravity. In Ken Shramm's The Compleate Meadmaker, Ken says around what gravity to shoot for, but he doesn't say why gravity is important or what effect the gravity has on the mead.

If I want less gravity, I add more water/juice right? If my gravity is too low, do I add more honey? If my carboy is already full, I guess I would have to pour some out, right?

05-24-2004, 01:45 PM
Interesting Question.

I have been meaning to get Ken's book for a while now. Let me address the subject without refrencing his targets, cause i don't know what they are.

Gravity measures how heavy your Must is compared to pure water. Water on this Scale = 1.0000.

Specific Gravity (SG): you are measuring the weight of the water with the disolved sugar (the main ingredient in honey) and other flavor components. The truth is that other flavor components are pretty negligable on thier effect on S.G. so we disreguard them. What we are really measuring is how much sugar per unit of volume is in the must/wine.

Original Gravity: This is a SG measurement before piching your yeast. This tells us how much Alchohol could be produced if fermented to dryness. Can also be used to estimate Alcohol by Volume in a finished mead. With less accuracy you can predict the residual sweetness based on your yeast selection and probable results.

Final Gravity: After fermentation is complete, this measures the S.G of the water, alcohol, and Sugar of the finished mead. The sweetness of your wine has a very definite affect on presentation.

A dry wine (0.995 F.G. would be dry) leaves a dry sensation in the mouth. The thin mead causes water/saliva in the mouth to be disolved and swallowed with the wine. Lacking sugar , the saliva glands aren't stimulated. Straight distilled beverages go further sucking water out of the surface cells... "burn all the way down"

A sweet wine is thicker, and the sugar stimulates the saliva glands. 1.03 F.G. wouls be a sweet finished wine.

I hope this helps... if you need more clarification please ask... this is a first draft.

05-24-2004, 10:17 PM
This clears up alot of confusion for me, but I'm still a little confused. So if someone is shooting for a certain dryness/sweetness, that's when they shoot for a certain gravity? How do they know exactly what gravity to shoot for in this relation?

What's the routine you use for checking the gravity? How often do you do it and at what stages? What would one do if the gravity was too high or low?

05-25-2004, 03:26 AM
If I might have a go at this one...

The main reason gravity is of interest is because measuring the change in gravity during fermentation will give you a fairly accurate idea what the alcohol content of the finished mead is. To measure it, you need a hydrometer. It looks like a tube with an elongated bulb on one end and set of measurments on the other. Depending on the gravity it will float at different depths.

The most important measurments will be the original gravity (O.G.) before you start fermentation, and the final gravity (F.G.) once everything is completed. It's a good idea to check a few times while the fermentation is taking place just to make sure everything is progressing nicely. The gravity should be dropping as the yeast converts dense sugars into lighter alcohol.

Most hydrometers also have a potential alcohol scale marked on them. The potential alcohol scale is basicly a measure of the same thing, but I find it a bit more intuitive than the specific gravity readings. If your original reading says you have about 14% potential alcohol, and your final measurment says you have about 2% left, you know the yeast has converted the difference (12%) into alcohol.

If you are following a recipe you won't have to worry about aiming for a certain gravity. The recipe may quote a certain O.G. or F.G. just so that you know your measurments are in the right ballpark.

Hope that helps.

05-25-2004, 09:58 PM
I might add to this by saying ....
Starting Gravity is very important in the case of many yeasts. A very high starting or OG (original gravity) , say higher than 1.130 may cause a fermentation not to start because of too high a concentration of sugar for a particular yeast. to avoid a stuck fermentation or a very slow start, it is always wise to investigate the particulars of a yeast prior to starting with a higher starting SG than 1.100 until you become familiar with a yeast's specifications and tolerances. Below is a useful reference chart for lalvin yeasts
Of course, if you are following a proven recipe, this might not be a concern, but is a good reason not to change the recommened yeast without prior investigation. Hope this helps someone. :)

05-26-2004, 01:12 AM
This clears up alot of confusion for me, but I'm still a little confused. So if someone is shooting for a certain dryness/sweetness, that's when they shoot for a certain gravity? How do they know exactly what gravity to shoot for in this relation?

What's the routine you use for checking the gravity? How often do you do it and at what stages? What would one do if the gravity was too high or low?

Last question first. I check it when I make the must. When I bottle, and I check it every time I rack... this lets me drink the hydrometer sample and see how things are going :-).

Ok, this is where accuracy diminishes. Lets take an example of my favorite yeast. K1-v1116.


The K1V-1116 strain is a rapid starter with a constant and complete fermentation between 15° and 30°C (59° and 86°F), capable of surviving a number of difficult conditions, such as low nutrient musts and high levels of SO2 or sugar. Wines fermented with the K1V-1116 have very low volatile acidity, H2S and foam production.

The K1V-1116 strain tends to express freshness of white grape varieties such as Sauvignon Blanc, Chenin Blanc and Seyval. The natural fresh fruit aromas are retained longer than with other standard yeast strains. Fruit wines and wines made from concentrates poor in nutrient balance benefit from the capacity of K1V-1116 to adapt to difficult fermentation conditions. Restarts stuck fermentations.

Will show this yeast is competitive, taste nuetral, and quickly ferments from 12-14% ABV (in my experience this is fairly consistently 12.5% with a small variance). Also note it is a robust yeast in low nutrient and or high gravity musts... (i did pitch it successfully in must of 1.17)

So to target a residual sweetness of around 1.025 for instance (i like my cyser sweet)... I check my hydrometer... says that is a potential ABV of 3.? %. If i want to end with 3+% potential, and the Yeast is going to make 12.5% potential ... i need 15.5% potential to start (if i don't want to sweeten at the end, but we aim a bit low so we can add if needed, tough to take sugar out at the end.) Again refrencing the hydrometer..... We will make the O.G. of the must 1.114 and pitch k1-v1116.

The results should be about 1.02, but if this yeast goes to 14% we will end at 1.008 or so. In my case, I'd sweeten with Apple Juice concentrate, and possibly some honey if below 1.020

Hope this helps.

07-23-2004, 03:49 AM
Ok folks... stupid question time.

I did NOT do an SG measurement of the must when I threw it together. Is this required to have an accurate SG when the mead is bottled? I know that I have to measure the SG when it's bottled, but somewhere I think I read where it's more accurate if you use a comparison between the SG when the mead is first thrown together and when it is bottled.


07-23-2004, 12:17 PM
You can measure your gravity when you bottle and the reading will give you an abstract idea of how sweet your mead is. However, if you didn't measure when you started, you won't be able to calculate just how much alcohol has been produced.

07-24-2004, 10:45 PM
I buzzed through Ken Schramm’s book and on page 64 he has a little approximate final specific gravity range for different meads as follows:

Dry Meads: 0.990 – 1.006
Medium Meads: 1.006 – 1.015
Sweet Meads: 1.012 – 1.020
Dessert Meads: 1.020 +

Remember that specific gravity is the ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water at 4°C (39°F).

Hope that helps,