Refractometer WAY off...

So, somehow, both my hydrometers are broken.  Kegged a couple different batches yesterday, thought I’d pull out the refractometer.

Calibrated it with distilled water, read 0 brix.  Put a few drops of my new beer in there.  8.5 Plato?  Really, that’s roughly 1.034 FG, after five weeks in the primary.

I have noticed a few threads on HBT that other people have had the same problem.  I’ve had the refractometer for a couple years, so returning it is out of the question.  Is it useless?  Should I toss it?

I borrowed a friends hydrometer and sampled the same beer, it finished at 1.010.  Right where I expected it.

This is the refractometer I have: http://www.rebelbrewer.com/shoppingcart/products/Economy-Refractometer.html

You have to correct for the alcohol in the finished beer. Try this…
http://seanterrill.com/2012/01/06/refractometer-calculator/

And even the corrected reading can be off. I only use my refractometer pre-fermentation. Never have been able to get an accurate reading post fermentation.

I agree with both of the above - you need to correct and Sean’s spreadsheet is the best I’ve tried.  But I still use my hydrometer post fermentation, no (potentially inaccurate) correction needed.

Out of curiousity which number from Sean’s calculator do you guys use. I see New Cubic, new Linear etc.

Sounds like you’re looking at the spreadsheet.  Just use the online calculator instead…

http://seanterrill.com/2012/01/06/refractometer-calculator/

excellent, thanks Joe

Man, I feel like I must be smiled upon… I do this all the time and everytime I’ve checked if I’m off it’s my a point or two… which is close enough for my needs.

My refractometer is always within a point of my hydrometer. They’re the greatest things since sliced bread.

I have the same issue with mine.  The OG is spot on and the FG is not even close.  I’ll try this spreadsheet.  Thanks for posting as it was driving me crazy!

Dave

This thread reminds me that I need to calibrate my refractometer one of these days.

I’m with Drew on this and can say that the refractometer is always off 1 point or less on my FG.

For those not using a conversion tool (spreadsheet or online) you cannot expect the direct reading to be accurate in any way.  As was said earlier, the alcohol in solution changes the refraction.

Paul