Plus, I understand testing for brix in a fermented must is not going to be correct after fermentation begins.
Allie
Plus, I understand testing for brix in a fermented must is not going to be correct after fermentation begins.
Allie
Hydrometers are build for measuring dissolved materials in
water. So when fermentation begins the must is no longer only water. It is a mixture of alcohol and water. Therefore hydrometer readings will be off.
This is
one of the reasons why I posted (in another thread) that transferring from primary to secondary by judgement of the hydrometer readings is not good winemaking practice.
Be aware that the table pays a lot of attention to temperature corrections, more as is actually needed.
As you can see in the table that each degree Celsius gives an off reading of 0.07 brix. You can derive that from the last column in which you can see the value each times increments 0.07 with each degree celsius. So 10 dergrees celsius would give an off reading of 0.70 brix.
This means that the potential alcohol would differ less as an half percent if the temperature would be 30 degrees celsius (86 degrees F)
So temperature readings are important but if the reading is within a few degrees of the calibration point of the hydrometer, don't worry about it.
Also be aware that a hydrometer does NOT only measures the amount of sugar in the must. It measures ALL dissolved materials in the must: sugar (the main part), acid, tannin, color components etc etc etc.
Two years ago I made my own SG table which does takes this in account. If you are interested you can download it as a PDF file from my web-log in a link on the right side of the page halfway down the column where it says: Luc's SG tabel
http://www.wijnmaker.blogspot.com/
So any hydrometer reading is an estimate of the amount of sugar in a must.
This last point can be easily demonstrated, and I already planned to do a demonstration of this on my web-log:
Take a measuring jar and fill it with yoghurt.
Now put the hydrometer in.
The reading will be sky-high despite the fact that there will be almost no sugars dissolved in it. And if there is sugar in the yoghurt it will likely be the non-fermentable lactose. And yoghurt is just water with several ingredients dissolved in it......
So please be aware that a hydrometer is just an aid and the rest is up to your own judgement.
Luc