Refractometer

[DandyMason]

Hey Guys,

So I just bought a refractometer off ebay... I knew the refractometer has this ATC (automatic temperature compensation) but shortly after buying it, I found out this refractometer can only accurately correct within the range of 50 and 86 F. I started looking around a bit more and I found out quite a few refractometers have these temperature ranges... I know quite a few ppl who use the refractometer from hopdawgs with boiling liquids (my refractometer looks identical to the hopdawgs one), so I got in touch with the guy from hopdawgs for some information, he really did not know the answers to my questions and he said he would need to get back to me, although he hasnt yet... and that was a few weeks ago.

Anyone familiar with any of this? Maybe the small amount of liquid needed for the refractometer is able to cool down within that range quickly enough that it is able to read boiling liquids fairly accurately? Its really not that big of a deal either way to me... but I was definitely expecting to be able to take readings of hot wort.

Also, anyone who has a refractometer, can you describe how to calibrate it right?

[Richard]

Maybe the small amount of liquid needed for the refractometer is able to cool down within that range quickly enough that it is able to read boiling liquids fairly accurately?

A single drop is going to lose heat really quickly to the surrounding air or whatever else it's in contact with... So assuming your ambient temperature is within that range, I'm guessing you'll be fine.

[fakr]

I usually put a couple of drops of boiling wort on the prism and let it sit for a minute or so before taking a reading.

Mine's also an ATC model.  I'm pretty sure the auto temp correction refers to the ambient temperature of the room you are in and not the liquid you are testing.  Non ATC models need to be calibrated according to the room's temperature.

you need such little liquid that it cools off to the temp of the glass prism within seconds.

[fakr]

very cool rigs...until you have to start using a spreadsheet to calculate gravity readings after you pitch your yeast...but still worth it.

[DandyMason]

Yeah I actually just read that... The ATC refers to the ambient temp. How did you go about calibrating yours fakr? Just go to a 68F room, place distilled water on the prism, and adjust the reading to 1? Thats what I have been reading....

So the refractometer becomes less accurate after pitching yeast because theres alcohol in it right? I also read that there is a 'wort calibration' ... because refractometers are made for pure liquid and sugar, and wort has more than just sugar.... know what im talking about at all? Cause I really dont ... hahaha

http://www.homebrewtalk.com/wiki/index. ... ractometer

[Dean]

more info here:

http://www.byo.com/stories/projects-and ... actometers

[JohnQ]

Don't know about other software, but Beersmith includes a conversion formula built in.
You need the OG and the current Brix, then Beersmith extrapolates the current gravity for you.
It's worked a charm for me.
JQ

[DandyMason]

Good to know there is still a way to use the refractometer after pitching yeast. Do you guys still use hydrometer to verify at all?

[fakr]

To be honest, I take brix readings and just multiply by 4 to get my SG readings.
10 brix on the refractometer ends up being 1.040 SG.  There is a small variation when you get up into high gravities like lets say a brix reading of 22, which ends up being 1.092 and not 1.088.

I've never calibrated mine...tried regular tap water and got a reading somewhere between 0 and 1.

I did verify using a hydrometer when I first got the refrac.  the hydrometer was reading 1.042 and the refrac was reading somewhere between 10 and 11 brix.  close enough for me.

when I pressure ferment, I take SG readings with the refrac as well.  I just tip the keg on it's side, take a small glass, put it over the gas out post, use a sanitized end of a pen to push the poppet in, get a small spray of beer in the glass, let the foam dissipate, and take a couple of drops for the refrac.  works quite well actually....would definitely make too big of a mess trying to get enough for a hydrometer.

[DandyMason]

Okay thanks guys for the information. I e-mailed the guy I bought it from and he gave me the following info for calibrating....

Instruction:
Open the daylight plate and place 2-3 drops of distilled water on the main prism. Close the daylight and press it lightly so the water spreads across the entire surface of the prism without air bubbles or dry spots. Alllow the sample to remain on the prism for approximately 30 seconds. Then adjust the calibration screw until the light/dark boundary coincides with the null line(0).  


Note?
Adjustment of the refractometer with the temperature compensation function should be made under the confition of 20 C degree enviromental temperature. When working temperature of the room or environment(not the sample) changes by more than 5 F degree, we recommend recalibration to maintain accuracy.

[DandyMason]

Also anyone know where I can track down one of these spreadsheets that calculates the gravity after pitching yeast?

[fakr]

Here's a real easy one:

http://www.brewheads.com/refract-currentgrav.php

Just make sure you have your original brix reading, which is used to calculate the current SG of fermentation.  The real formula is deadly long...

and a bunch of other calculators that are useful:

http://www.brewheads.com/calc.php

[Dean]

... The real formula is deadly long...

hahaha:  SG = 1.000019 + [0.003865613(Brix) + 0.00001296425(Brix) + 0.00000005701128(Brix)]

[fakr]

Smart ass!

[DandyMason]

Perfect! thanks