Refract Or Hydro

[Ash in Perth]

Just racked my APA into secondary. The hydro says its 1.012, the refract says 5.8 (1.008 eq.) OG was 1.048 from refract only. which one should i trust and use for the final grav?

cheers

 

[razz]

Have you made an adjustment to the refractometer due to alcohol in the FG ? Did you note the temp of the sample so that both instruments will give accurate readings ?

 

[Ross]

Just racked my APA into secondary. The hydro says its 1.012, the refract says 5.8 (1.008 eq.) OG was 1.048 from refract only. which one should i trust and use for the final grav?

cheers

If your hydrometer reads 1.000 in water of the same temp - trust the hydrometer. The calculations involved once the beer starts to ferment, make the refrac a bit hit & miss. Plus you get to taste your hydrometer sample.

cheers Ross

 

[Ash in Perth]

I put the brix reading into promash and it told me the FG. beers at 19Deg so this is about the right temp for both i think.

The hydro is calibrated for 20DegC and the refract has automatic temp compensation apparently.

Cheers

 

[Ash in Perth]

the hydro reads water as being a bit lighter than water (0.996) and it was only tap water. think i might trust the refract

 

[Andyd]

I commonly get the same difference you're experiencing. Like the boys have said, the alcohol content begins to have an effect on your Refractometer reading, particularly at the end of fermentation. The first time I used my refract, I couldn't figure out why my wheat beer wouldn't finish out to 1012. Guess what - it had!

I haven't done the experiments yet, but you should be able to compensate based on the alcohol content - the biggest challenge is that this is not constant over the fermentation cycle. I rather suspect that the end result will be that it takes twice as long to use the refract for this than the Hydro, and at least with the Hydro you get the sample at the end.

If I can't figure out the compensation, My R may well become another one of those bits of brew kit that gets relegated to the Shrine of Bunnings (you know - that corner of your garage filled with all the bits you saw at Bunnings on your numerous trips and thought "S**T ! That would be useful - better get me one of them!")

Andy

 

[pint of lager]

There was exactly the same thing posted up within the last two weeks. Use one or the other.

The hydrometer measures density. It is trying to measure a malt sugar solution which is more dense than water plus alcohol which is less dense than water. The end result is skewed.

The refractometer is measuring the refractive index and also suffers from the problem of measuring a solution that contains components of different refractive indices.

Neither is perfect. Most people incorrectly think the hydrometer is right, because that is what they are more familiar with.

 

[Ash in Perth]

Shouldnt promash calculations take this into account? i thoguht they did, at elast for the hydro.

 

[T.D.]

I think there is a reason why wineries and breweries use hydrometers to monitor fermentation etc rather than refracs. Refracs are great to indicate what the sugar level is in the lead up to fermentation (great things to have out in the vineyard when trying to decide when to pick) but if the commercial trend of using hydrometers at later stages is anything to go by I'd say they are more accurate.

 

[Ash in Perth]

large breweries tend to use machines that do everything. jsut insert a sample and the machine tells you gravity, colour, alcohol and acouple of other things. i tihnk its called an alcolyzer.

it makes sense that others use hydros (except i know the czechs use refracts) they would by much easier to compensate for the alcohol being produced.