Hydrometer Table and/or chart conflicts?

[bricklayer67]

I am about one year into my home winemaking hobby, and I have been relying on various websites for most of my information. Now that I am starting to finish and bottle some of my first batches, I am having to use some math skills to calculate how much sugar to add to achieve a particular sweetness and also how much liquid to add to get to a particular alcohol %. The latter is because mainly when I first started, the yeast that was recommended to me was a sure fire Lalvin EC1118, which grows easy enough but also reaches 18% without breaking a sweat! So after doing this math just once, I decided to create an Excel spreadsheet in order to simplify things. So I got out a hydrometer chart that came with my hydrometer, but the numbers didn’t match the USDA Table 114, and neither chart matched that which is on Jack Keller's site either. So, how do I know what information is correct? How important is it that it BE correct? For instance, I use yeasts that will die off at the percentage that I want to end up with now, but even still a Cotes de Blanc will push 14% sometimes, and maybe I only want 11 or 12? But are my readings correct in the first place? After all, my hydrometer is based upon a chart that says if my must started at 1.12, and my fermentation ended at 1.01, I’m already at 14.3%. But according to the USDA Table 114, I’m at 15.0%, and Jack Kellers chart says I’m at 14.9%. Can you see my dilemma? Any advice?

 

[Luc]

First read this:

http://wijnmaker.blogspot.com/2010/11/vertouw-je-je-hydrometer-trust-your.html

The story is this. I did an SG measurement with my hydrometer which was totally correct. Then I looked at the sugar scale on my hydrometer and it was way off.
So I did some more tests and they all gave different readings as my hydrometer did. Then I had conversations with the manufacturer of the hydrometer and that was really hilarious. Read the story.

Another story on this subject was this:
http://wijnmaker.blogspot.com/2007/03/hoeveel-suiker-zei-u.html

It is not yet translated in English but just look at the tables in it.

I took al my winemaking books and analysed the SG tables in them.
The differences were quite big !!!
Some tables expected the yeast to use almost 20 gram sugar to make 1% alcohol. Others expected that only 16 gram was needed.
That is a whole lot of a difference.

So I made my own table. You can download that here:
http://www.mediafire.com/?sjcvgeebjqn

It is based on a formula which I estimate as the most reliable.

The formula is as follows:

If acidity is less as 6

Sugar = (2.6 x oechsle) - 20

If acidity is between 6 and 10

Sugar = (2.6 x ochsle) -25

When acidity is larger as 10

Sugar = (2.6 x ochsle) - 30

Oechsle is SG - 1000

So if your hydrometer reading is 1080 oechsle is 80.

The formula is based on the following.

Each point in SG reporesents 2.6 gram sugar.
This can be easily verified.

However there are some things that are in the must and SG reading that are no sugar. Think acid, tannin, colour, flavor, nutrient etc etc etc.

Therefore a certain amount is subtracted..

The differences in the charts from your hydrometer, Jack, the US chart, Pambianchi's chart etc etc etc are all for some obvious reasons.

First not all juice is equal. Grape juice is not equal to bananajuice or cherry juice. So the readings at the same sugar level will be different in these juices. this is due to above mentioned reasons (acid tannin nutrients etc)

Second.
Not all yeast is the same. There are yeasts that indeed produce 1% alcohol from 19 gram sugar and there are yeast that only need 16 gram sugar.
Therefoer at the same SG alcohol prediction might vary a lot.
Do the math.

So no two scales are likely to be the same.

That is why I develloped my own scale which proved to be quite accurate during all the years I made wine.


Luc

 

[pkeeler]

Only thing I could add to Luc would be that not all hydrometers are calibrated to the same temp. I would use the chart that came with your hydrometer unless you are sure that the calibration temps are the same.

 

[bricklayer67]

Wow!

Luc, I can't thank you enough for the information, it will take me some time to sort through, but you have done an enormous amount of work on this. Very much appreciated!

 

[djrockinsteve]

Luc, I can't thank you enough for the information, it will take me some time to sort through, but you have done an enormous amount of work on this. Very much appreciated!

Luc's the scientist of our forum. You can learn a lot from his posts/threads. You can even learn a second language.