which hydrometer to trust?

[dereknobleluke]

So we all take origional and monitor gravities throughout the fermentation. Which one should we trust when we are actually trying to discover how much alcohol is in the beer/wash and the calculation that goes along with it?

We have been doing some experiementing with molasses brews that start super high (measured in brix--31.5, and another one 27.8 plato). If we convert these initial and final readings over to the hydrometer readings and multiply them by .102 (a standard reference that takes into account average nutrient uptake and metabolism of yeasts without alcohol conversion), vs OE-AE times 4.5 (w/w) or 5.5 (volume) we get different results. And further yet we get even different results than expected upon the distillation (granted there may be some higher weight alcohols still within the wash itself).

Just an idea towards what others without expensive EtOH monitors are doing to quote their alcohol levels...

Are these hydrometers linear throughout their glass columns...?

[Larry Horwitz]

the hydrometers are only as good as their cal trail (are they NIST or equiv?)...but you should be aware that the number you are calculating is highly unlikely to be what the actual alcohol number is. A lab test is the only way to be sure...otherwise you are just guessing no matter how good / bad the instrument.

[gitchegumee]

The way I learned to take accurate measurements of alcohol in either beer or spirits was to distill all the alcohol in a 100 ml sample of wash, dilute the pure alcohol from the sample back to 100ml with pure water, and use a special alcohol hydrometer to measure the alcohol. This is a simple technique of removing the effects of sugars and proteins and substituting pure water for the wash. It is accurate. Good luck!