Degrees Plato are used in the brewing industry to express the concentration of extract (dissolved solids, mostly sugars) in a wort or beer as a percentage by weight. Thus 100 grams of a 12 degree Plato (abbreviated 12 °P) wort contains 12 grams of extract. In 1900 the Kaiserliche Normal-Eichungskomission, under the leadership of Fritz Plato, measured the specific gravity, to six decimal places, of pure sucrose solutions of known strength by weight and published tables of these values.

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  • Degrees Plato are used in the brewing industry to express the concentration of extract (dissolved solids, mostly sugars) in a wort or beer as a percentage by weight. Thus 100 grams of a 12 degree Plato (abbreviated 12 °P) wort contains 12 grams of extract. In 1900 the Kaiserliche Normal-Eichungskomission, under the leadership of Fritz Plato, measured the specific gravity, to six decimal places, of pure sucrose solutions of known strength by weight and published tables of these values. These tables are more accurate than earlier, similar tables published first by Bohemian scientist Karl Balling (specific gravities determined to 3 decimal places) and later by German Adolf Brix. The original Plato table lists the density of wort at 20 °C normalized by the density of water at 4° C and the entries thus represent true specific gravities. In a modern table, exemplified by the one published by the ASBC, the data from the Plato table have been mathematicaly adjusted for the effects of air on the instruments used to measure specific gravity and normalized to the density of water at 20 °C. Tabulated specific gravities are, thus, apparent specific gravities and usually written with the annotation (20°C/20°C) to indicate that both sample and water reference temperatures are 20 °C.. Similar tables are in use by the EBC in Europe. As the Balling, Brix and Plato tables differ but slightly in the values of specific gravity reported for a given solution strength (grams sucrose per 100 grams solution) they are more or less interchangeable and Brix units are, for example, the standard in the fruit juice, soft drink, sugar and wine making industries. To determine the extract content of wort a brewer measures the (20°C/20°C) apparent specific gravity of the wort using a hydrometer, pycnometer or oscillating U-tube electronic meter and then enters the ASBC or EBC tables with the value determined taking out the corresponding °P. The ASBC table can be fit by the third order polynomial <math>P = -616.868 + 1111.14(SG)-630.272(SG)^2 + 135.997(SG)^3</math> and as this is published by ASBC in their Methods of Analysis, carries the same authority as the table itself. Note that electronic instruments will have this polynomial built in so that they read directly in °P. Many brewers, particularly home brewers, like to think in terms of "points" defined as <math> p_t = 1000 \times (SG-1) </math> so that, for example, an SG of 1.040 would be equivalent to 40 points. Substituting <math> SG = (p_t/1000) + 1 </math> into the ASBC formula, expanding the binomial terms and summing the coefficients of like powers of <math> p_t </math> gives the equivalent of the ASBC polynomial in terms of points <math>P = -0.003 + 0.258587p_t - 0.00022281p_t^2 + 0.000000135997p_t^3 </math> This is entirely equivalent to the ASBC formula and will compute exactly the same answer for a given specific gravity for those who prefer to work in points. Of equal significance is that there is apparently a near linear relationship between points and degrees Plato with the proportionality factor being close to 1/4 for the range of specific gravities of most interest. To obtain Plato from points, therefore, most home brewers simply divide points by 4. For SG 1.040 this yields 10 °P whereas use of the full formula or the ASBC table would give 9.993 °P. For SG 1.080 this very simple conversion yields 20 °P whereas the full formula gives 19.328°P. A second order fit to the ASBC tabulated data yields, in factored form, the simpler (relative to the ASBC polynomial) formula (referred to as the Lincoln Equation): <math>P = (463-205*SG)*(SG-1)</math> At SG 1.040 this formula yields 9.992 °P and at 1.080 it gives 19.328 °P so it is clearly adequate for most purposes. In calculating °P from specific gravity measurement the brewer is actually determining the amount of pure sucrose which would be found in an aqueous solution of the same specific gravity as his sample. While the typical wort contains only a small percentage of sucrose other sugars behave remarkably similarly to sucrose with respect to the specific gravity of their aqueous solutions so the extract found by this method is an accurate estimate of the extract in the wort except in cases where the brewing liquor is high in dissolved minerals. Because of the 1 to 1 correspondence of specific gravity and extract content a conventional hydrometer can be marked in units of °P (or Brix or Balling). As the corrections elucidated by the Eichungskommission were in the fifth and sixth decimal places with respect to the Brix measurements such markings on a typical immersion hydrometer could represent either Brix or Plato. Many hydrometers sold today are marked in Brix/Plato and this leads to the common misconception that °P is another "scale" for specific gravity. It is not. It is representative of the mass of extract in a given mass of solution. Sucrose solution strength (w/w) can also be measured by a suitably calibrated refractometer. As these are primarily used in the fruit juice, wine, sugar and similar industries they are usually calibrated in Brix. These instruments are sometimes used by brewers. The Brix reading can be considered to be the same as Plato readings which is a good assumption for all but the most precise work. To make calculations such as the ones in several of the examples which follow in the Applications section one must obtain the specific gravity number corresponding to the measured Brix value. This can be done by using the ASBC (or EBC) tables or by using one of the conversion methods under Calculation of Specific Gravity Equivalent to °P. Consumers on the European continent are more familiar with Degrees Plato than in the US. They are frequently listed on German beer labels as the Stammwürze. Slovak and Czech breweries also label their beers with the original gravity in °P though they will often print simply "12%" for a 12°P beer.
  • Le degré Plato (notée °P) est une unité établie en 1900 utilisée dans le brassage de la bière. Il correspond au pourcentage en masse d'extrait sec du moût avant fermentation. Le degré Plato est équivalent au degré Balling, en plus précis. Les bières courantes sont brassées à partir d'une densité primitive de moût de l'ordre de 11 à 13°P L'unité tient son nom du D Fritz Plato, un savant allemand.
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  • Degrees Plato are used in the brewing industry to express the concentration of extract (dissolved solids, mostly sugars) in a wort or beer as a percentage by weight. Thus 100 grams of a 12 degree Plato (abbreviated 12 °P) wort contains 12 grams of extract. In 1900 the Kaiserliche Normal-Eichungskomission, under the leadership of Fritz Plato, measured the specific gravity, to six decimal places, of pure sucrose solutions of known strength by weight and published tables of these values.
  • Le degré Plato (notée °P) est une unité établie en 1900 utilisée dans le brassage de la bière. Il correspond au pourcentage en masse d'extrait sec du moût avant fermentation. Le degré Plato est équivalent au degré Balling, en plus précis. Les bières courantes sont brassées à partir d'une densité primitive de moût de l'ordre de 11 à 13°P L'unité tient son nom du D Fritz Plato, un savant allemand.
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  • Plato scale
  • Degré Plato
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