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Plato vs. specific gravity

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Buford

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I was just wondering why exactly we use specific gravity as opposed to Plato like most (all?) commercial brewers do. I personally have no idea what a Plato measurement means when I see it and have to convert since I've always used SG, but why do we use different units than pro brewers?
 

menschmaschine

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Don't quote me on this, but I believe in the food science or general science industry, pro-brewers are one of the only ones who use °Plato.

°Plato = percent extract (or "sugar", although it's not all sugar) by weight in solution. So, 10°P = 10% extract by weight. This makes things easy for brewing calculations.

Specific gravity relates to (instead of weight of extract) the weight of the whole volume of solution relative to an equal volume of water. So, a 1.060 volume of wort is 6% heavier than the same volume of water.

For brewing purposes, °Plato makes as much sense as using the metric system in everyday life (i.e., a LOT of sense).;)
 

Hegh

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Luckily, it's an easy conversion. Multiply the degrees Plato by 4, divide by 1000, and add 1. Or, in other words, 4 degrees plato = 1.016 SG.
 

davesrose

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I was in Asheville yesterday celebrating my dad's B-day. He wanted to go to a few local microbreweries there....one is a brand new one that's starting to get some awards. Anyway, when we were there, I peered through a window to catch the mash tuns they had. Brand new equipment and quite large to boot (quite a few 60 gallon fermentors taking up an old warehouse). Anyway, the thing that really caught my eye was a standard hydrometer conversion table taped on a mash tun...same one I use with my hydro readings.

My mom says she likes this place's IPA second best (next only to my "tongue splitter ale")....and yes, she's a great cook and likes hoppy beers. Some of her great food recipes use standard American and metric measurements (whatever is most popular for that particular group). In the long run, who really cares if the measurement is metric or some American measure? It's just a means to an end for keeping a correct proportion of ingredients/ABV.

It's like why do we Americans like using a U.S. standard of lbs, Brits like stones, and many countries like kilos....it just is! :)
 

HItransplant

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Or, IIRC

260 / ( 260 / P ) = SG
sorry to bump up an old thread but I just spent 30 min (with my wife) dragging algebra out of our very dusty math brains to find that this equation is wrong. I wanted to solve for P so that I could make a spreadsheet to compare plato and specific gravity.

when I solved for P in this equation, I ended up with this: P = SG.


the equation up a couple of posts seems to be correct and I was able to solve for P to make a spreadsheet that takes SG and spits out Plato. That way I can more easily compare.

thought Id share the plato equivalent of 1.01- 1.107. Id attach the spreadsheet but Im not sure I can or if I know how.

edit: now that I spent the time to solve for P, I realize I didnt need to.. hah!! anyway, maybe its helpful, maybe nobody cares. :cross:


SG Plato
1.01 2.5
1.011 2.75
1.012 3
1.013 3.25
1.014 3.5
1.015 3.75
1.016 4
1.017 4.25
1.018 4.5
1.019 4.75
1.02 5
1.021 5.25
1.022 5.5
1.023 5.75
1.024 6
1.025 6.25
1.026 6.5
1.027 6.75
1.028 7
1.029 7.25
1.03 7.5
1.031 7.75
1.032 8
1.033 8.25
1.034 8.5
1.035 8.75
1.036 9
1.037 9.25
1.038 9.5
1.039 9.75
1.04 10
1.041 10.25
1.042 10.5
1.043 10.75
1.044 11
1.045 11.25
1.046 11.5
1.047 11.75
1.048 12
1.049 12.25
1.05 12.5
1.051 12.75
1.052 13
1.053 13.25
1.054 13.5
1.055 13.75
1.056 14
1.057 14.25
1.058 14.5
1.059 14.75
1.06 15
1.061 15.25
1.062 15.5
1.063 15.75
1.064 16
1.065 16.25
1.066 16.5
1.067 16.75
1.068 17
1.069 17.25
1.07 17.5
1.071 17.75
1.072 18
1.073 18.25
1.074 18.5
1.075 18.75
1.076 19
1.077 19.25
1.078 19.5
1.079 19.75
1.08 20
1.081 20.25
1.082 20.5
1.083 20.75
1.084 21
1.085 21.25
1.086 21.5
1.087 21.75
1.088 22
1.089 22.25
1.09 22.5
1.091 22.75
1.092 23
1.093 23.25
1.094 23.5
1.095 23.75
1.096 24
1.097 24.25
1.098 24.5
1.099 24.75
1.1 25
1.101 25.25
1.102 25.5
1.103 25.75
1.104 26
1.105 26.25
1.106 26.5
1.107 26.75
 

rico567

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There are converters available in several places on the Internet that will change SG <-> Brix with the touch of a key. For our purposes, Brix may be considered equivalent to Plato. On brewday, when I'm using my refractometer, all I do is multiply x 4 in my head, and it's close enough. For virtually all homebrewing, the idea that ± .002 - .003 point on FG is going to make any noticeable difference in the finished product is just trying to grind WAY too much point on a pencil.

As far as systems of measurement, there are plenty of historical references on the Internet (and real, paper books) that discuss this. Traditional systems (like the "English" - SAE, etc. system) are based on handy everyday units, what we might call "human." (e.g. human sized)

Science has come to use the metric system, which is very good indeed for science and industrial applications. But there is nothing natural/human in a milliliter or a microgram (as there actually WERE in furlongs and fortnights), nothing much in everyday experience corresponds to these things.....so maybe it shouldn't be used everywhere, despite those who believe it should be imposed on everyone, everywhere.

We believe it's OK to be bilingual, nobody these days would think it strange that I speak both English and Spanish (and enough German, Italian, French, Mandarin & Japanese to order beer), so why on earth would anyone believe that it's necessary to have The One True System of Measurement?
 
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Today I think I've decided to switch to Plato from SG for the simple fact that when taking a hydrometer reading in cloudy (wheat) beer the Plato scale is much easier to read i.e. 5ºP is approx 20 SG points which can be frustrating to get an exact reading on with the more bunched up scale. I like everyone else's reasons too.
 

DeafSmith

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thought Id share the plato equivalent of 1.01- 1.107. Id attach the spreadsheet but Im not sure I can or if I know how.

edit: now that I spent the time to solve for P, I realize I didnt need to.. hah!! anyway, maybe its helpful, maybe nobody cares. :cross:


SG Plato
1.01 2.5
1.011 2.75
.
.
.
.

1.106 26.5
1.107 26.75

The 4:1 conversion isn't exactly linear - it begins to diverge above about 11 Plato. By the time you get up to 1.084 SG, the Plato equivalent is 20.2, not 21. See Table 31, page 266 in the 3rd edition of Palmer's "How to Brew".
 

Bob

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The 4:1 conversion is worthless above 12°P (~1.048). Plato was arrived at empirically, not mathematically.

{Plato/(258.6-([Plato/258.2]*227.1)}+1 = Specific gravity

That'll get you very close indeed.

There are also a lot of charts available on the Internet. That's what I use when I'm using my refractometer on brew day, not an equation. ;)

Bob
 

livewir

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I asked a local Microbrew why they use plato and their answer was pretty straight forward, all the neato digital equipment they use to measure gravity is in plato.
 

Brewerforlife

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I am A pro-brewer, and still use my hydrometer most of the time. I do have both, A refractometer for quick pre-ferm measurements, and a set of 3 (plato) sacchrometers. The problem with the sacch. is it takes such a large sample jar, becuase the sacchrometer is so large. It takes a set of 3 to cover the whole range of a standard S.G hydrometer, so they are a little more accurate & easier to read becuase of the large distance between increments. There is a good conversion chart in Palmer's book on page# 266. He also states that : wort deg. Plato is= deg. Brix divided by 1.04. You can get a set of sacchrometers at Crosby&Baker for around 60$. Probably a waste of money at homebrew level, because of the large sample needed. Hope this help's. Cheers!!!
 

KFBass

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Im at a weird cross roads in brewing calcs. I work in a brewery and we use palto, celcius, and kilo's since we're canadian. I was brought up homebrewing reading this forum and popular books so most of the time im converting to SG, F, and lbs. Tho I'm starting to understand it a bit better in Metric. The problem is 122F doesnt have any relavance to me but 30C does.

We use plato hydrometers, with different ones calibrated for sg and fg. I do it cause my brewmaster does it. And I probably keep on doin so cause that's the language of the industry. Same in music, we speak strange terms cause everyone else does and its how we can communicate.
 

KFBass

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As far as systems of measurement, there are plenty of historical references on the Internet (and real, paper books) that discuss this. Traditional systems (like the "English" - SAE, etc. system) are based on handy everyday units, what we might call "human." (e.g. human sized)

Science has come to use the metric system, which is very good indeed for science and industrial applications. But there is nothing natural/human in a milliliter or a microgram (as there actually WERE in furlongs and fortnights), nothing much in everyday experience corresponds to these things.....
To give some reference, 1kg = the mass of 1L of water, almsot exactly. 1gm is = to 1ml of water or 1cc of water at Standard temp and pressure. There is also the nature of mass vs weight. You will weigh more in lbs on jupiter due to the nature of gravity, though your mass in kgs will stay the same. Also, work is being done now to have the kg based on Plank's constant rather then a man made-ish artifact.
 

Bob

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+1 to the set of calibrated Plato hydrometers/saccharometers. I don't know where I'd be without mine; I've had them since my earliest days brewing professionally.

I don't really perceive losses with the sample size on a homebrew scale, because I factor them in to start with. :D And I take samples far more often than most homebrewers, because I like to practice yeast management.

I like to use the appropriate tool for the job. In the brewhouse, it's my refractometer. In the rest of the production chain, it's saccharometers.

Those different scale saccharometers are a GODSEND when you're learning. They're infinitely better tools than the standard LHBS hydrometer, because they're so much more precise. It's like a grocery-store dial thermometer vs. a calibrated digital unit; both will work, but the digital unit is more precise.

Also +1 to thinking about temperature in Celsius, especially for step mashes. ;)

Cheers,

Bob
 

jc3375

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Luckily, it's an easy conversion. Multiply the degrees Plato by 4, divide by 1000, and add 1. Or, in other words, 4 degrees plato = 1.016 SG.
over sp gr of 1.020 this equation doesn't work, here it is exactly:

{Plato/(258.6-([Plato/258.2]*227.1)}+1 = Specific gravity
 

patto1ro

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Don't quote me on this, but I believe in the food science or general science industry, pro-brewers are one of the only ones who use °Plato.
Professional brewers in Britain generally use specific gravity. Though even that only really caught on in the 20th century. Before that they mostly used brewer's pounds (which I prefer, personally). For weight measurements they generally use kilograms, though the volumes are in a mixture of barrels and hectolitres.

I suspect the use of Plato in the USA comes from the influence of German brewers in the 19th century.
 

wailingguitar

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While the post showing the long list of SGX=PlatoY showed **.*Plato, no one (unless I missed it) as mentioned the decimal point in the Plato reading. Another of the many reasons that Plato is used in commercial breweries is that it gives a greater degree of accuracy than SG... not majorly so, but it does
 

TravisRichard

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I am still confused by all this. First, is there a way to measure only the amount of sugar in wort/beer, without also measuring proteins and other materials dissolved in the beer/wort?

Second, if SG is the weight of a (sugary)liquid in relation to the weight of pure water and if degrees Plato is the percent of sugars dissolved in a liquid by weight, then why doesn't 1.1 SG = 10 Plato?
 

DeafSmith

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Second, if SG is the weight of a (sugary)liquid in relation to the weight of pure water and if degrees Plato is the percent of sugars dissolved in a liquid by weight, then why doesn't 1.1 SG = 10 Plato?
I am not a chemist, so I could be wrong about this, but here's what I think happens. First, if I remember correctly, Plato is the weight of dissolved sugars as a fraction of the total weight of the solution, so 10 Plato would be, for example, 10 grams sugar and 90 grams water. The specific gravity, on the other hand, measures density, that is, the weight of the solution divided by its volume. When you add sugar, the volume of the solution expands to make room for the sugar molecules, so while a 10 Plato solution weighs 100/90 = 1.11 or 11 % more than the water you started with, the solution takes up more space than the original water. The SG would be 1.11 only if you could have added the sugar without the volume increasing. If the SG for a 10 Plato solution is 1.04, then the solution must have expanded to 1.11/1.04 = 1.0673, or by 6.7 %.

To put it another way, you start with 90 grams of water and add 10 grams of sugar to get a 10 Plato solution with a SG of 1.04. The solution weighs 11 % more than the water you started with, but has a volume 6.7 % greater than the original water, so the SG = 1.11/1.067 = 1.04.
 
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