Every time you open the fermenter, you are risking infection from airborne microbes. Proper yeast preparation should prevent this problem.īeginning brewers often make the mistake of checking the gravity too frequently. The brewer should only be concerned about a high hydrometer reading when primary fermentation has apparently ended and the reading is about one half of the OG, instead of the nominal one forth. The hydrometer should be regarded as only one tool available to the brewer as a means to gauge the fermentation progress. It needs to be emphasized that the stated FG of a recipe is not the goal. A couple of points either way is not unusual. For example, a typical beer OG of 1.040 should finish about 1.010 (or lower). For an average beer yeast, a rule of thumb is that the FG should be about 1/4 to 1/5 of the OG. Beer recipes often list the Original and/or Final Gravities (OG and FG) to better describe the beer to the reader. Liquid gravity (density) is dependent on temperature and temperature correction tables are usually sold with the hydrometer or are available from chemistry handbooks.Ī hydrometer is a useful tool in the hands of a brewer who knows what wort gravity is and why he wants to measure it. Hydrometer readings are standardized to 59☏ (15☌). Champagnes and meads can have gravities less than 1.000, because of the large percentage of ethyl alcohol, which is less than 1. Beers typically have a final gravity between 1.015 and 1.005. Attenuation is the conversion of sugar to ethanol by the yeast. The hydrometer is used to gauge the fermentation progress by measuring one aspect of it, attenuation. Things You Can Do Differently Next TimeĪ hydrometer measures the difference in gravity (density) between pure water and water with sugar dissolved in it by flotation.Calculations for Boiling Water Additions.Using Salts for Brewing Water Adjustment.Manipulating the Starch Conversion Rest.The Starch Conversion/Saccharification Rest.What is Different for Brewing Lager Beer?.Water Chemistry Adjustment for Extract Brewing.However it would be suprising if it was anything other than 20✬ since the ASBC, EBC and IoB all use a definition of specific gravity that has a reference temperature and measurement temperature of 20✬. The short answer is that the calibration temperature is whatever is used by the online convertor. Since you're measuring an unknown mixture of sugars converting refractive index to Brix to SG is an approximate measure in anycase. However, you should realise that Brix is a measure of the concentration of a sucrose solution and is inferred by the refractometer by the measurement of refractive index. If the standard was defined at a different temperature then the specific gravity value would most likely be different since the thermal coefficient of expansion of the sample and water are usually different. Nowadays, for brewers at least, the SG of a sample is conventionally reported as its density relative to water at 20 degrees Centigrade. I believe the answers from Zymurgist and have missed the point. And generally people will use the same method to obtain their OG and FG so any small differences that might arise between methods should balance out if you're being consistent. But in practice this should be pretty small. For example if you used a refractometer for your OG that was normalizing the Brix value to 70✯, and a hydrometer for your FG that was calibrated at 60✯, I suppose some error could be introduced that might be worth accounting for. If you were using different methods for measuring your OG and FG, I suppose it's possible that you would need to take this into account. So provided yours does as well, you should be fine with just using the straight converted value. From what I've heard, refractometers usually adjust for temperature automatically. So you will want to make sure that your Brix value is temperature adjusted before you do the conversion. That is, if you start with the correct value in Brix, your converted SG value will be correct. Both Brix and specific gravity are temperature sensitive but the conversion seems to be independent of that fact.
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