Je suis en train d'acquérir un réfracto. Par contre, un peu perdu dans les unités Brix, Plato, Baume, % vol. etc...
J'ai bien trouvé un article sur la conversion de ces différentes unités en Densité spécifique (1000 à 1xxx), mais je cherche simplement à savoir quelle unité est la plus utilisée par les brasseurs et l'échelle.
Brou-Brou vend du 0-18 plato et du 0-32 Brix...
Vous avez une recommandation ?
Pour info, la conversion, non traduite
Mr. Wizard a écrit :Can you give me a formula for converting degrees Brix to specific gravity, or degrees Balling? I have a
refractometer and was told that I can check the gravity
of my run-off when sparging. It sounds good to me! That
way, I wouldn?t have to wait for a hydrometer sample to
cool. Also, it would be nice to just take a sample drop
to check gravity during fermentation.
Vicky Melius
via e-mail
Mr. Wizard replies: This question raises some issues of
semantics that make giving a clear answer difficult
without first addressing terminology. In general terms,
°Brix, °Plato and °Balling are interchangeable. All
three of these scales express the weight percentage of
sucrose solutions and relate this weight percentage to
specific gravity. The Balling scale is the oldest and is
based on Balling?s tables established in 1843. Brix
later corrected some calculation errors in the Balling
tables and introduced the Brix tables. In the early
1900s Plato and his collaborators made further
improvements and along came the Plato tables.
Essentially, they are the same, but the tables differ in
their conversion from weight percent to specific gravity
in the fifth and sixth decimal place of the specific
gravity number. Winemakers, the sugar industry and the
juice industry typically use °Brix, continental brewers
typically use °Plato, British brewers use specific
gravity multiplied by 1000 (for example 1.040 becomes
1040) and American brewers use a mixture of °Balling, °
Plato and specific gravity.
I use Plato and specific gravity because my hydrometers
indicate °Plato, and specific gravity is always
required when doing brewing calculations. For example,
if you multiply °Plato (expressed in decimal form) by
specific gravity, the result is kilograms of extract, a
convenient number when doing calculations. Now for the
conversion. The following formula shows the conversion
from specific gravity to °Plato.
{Plato/(258.6-([Plato/258.2]*227.1)}+1 = Specific
gravity
To make sure you are doing your math properly, convert
12° Plato to specific gravity. The correct conversion
yields 1.04838.
example:
{12/(258.6-([12/258.2]*227.1)}+1 = SG
{12/(258.6-(0.04648*227.1)}+1 = SG
{12/(258.6-10.5546)}+1 = SG
{12/248.0454}+1 = SG
{0.04838}+1 = 1.04838 = SG
If you have a refractometer, you certainly can use it to
determine density. Most refractometers are scaled in
terms of °Brix because they are most often used in
industries that use the Brix scale. For all practical
purposes, you can use the formula above for the
conversion. Use caution with your refractometer because
light refraction is temperature dependent just like
specific gravity. Your sample temperature should ideally
be around 68° F. The great thing about a refractometer
is that the sample size is small (about 1 mL) and very
easy to cool to room temperature before measuring.
I don?t like refractometers for two reasons. The first
reason is that they are difficult to read unless they
are really high-end. I do like these high-end ones (they
resemble a microscope) but they cost $5,000 new! The
second reason I don?t like them is that they are not
reliable for checking samples from the fermenter because
alcohol interferes with the measurement differently than
it does with a hydrometer. In other words, a hydrometer
measurement on beer may indicate 2° Plato and the
refractometer will indicate something different on the
same sample. Most brewers express the final gravity as
measured by a hydrometer. If you do want to use the
refractometer, use it on wort only and then you will be
fine.
source : http://groups.yahoo.com/group/BrixTalk/message/3292
"Une bière avec quelques défauts est préférable à un verre d'eau qui n'en a pas"
Indira Rindutou
