Refractometer reading?

[YOpassDAmike]

I used a refractometer to fin out my preboil gravity, it was 14 brix at a volume of ~7.5 gallons. I performed a 120 minute boil. I checked the gravity with the refractometer with 15 minutes left of the boil and I got a reading of 24 brix. After the 120 minute boil and cooling my wort, I checked my gravity in the fermenter prior to adding the geast and got a reading of 20 brix. When I cooled my wort I got it down to 70 degrees. My ending volume in the fermenter was about ~5 gallons. Hoow did my gravity go down? My refractometer is a ATC. I also want to say that I did not dilute my wort or anything with tap water. So I am confused, what is my original gravity? Thank you.

 

[Brewmasher]

Always use cooled wort. Refractometers have a range for ATC. Mine is 50- 86 F. You also have to check your specific instrument with a hydrometer and apply a correction figure as refractometers are calibrated for sucrose, which has a different refractive index than maltose. Even different worts will have differences depending on mash temps and grains used. If you brew the same general style, you will be pretty close, otherwise, it is recommended to average about 20 worts and treat it as such.

 

[kh54s10]

The small amount of wort that you are sampling will cool to ambient in just a minute or so. So, temperature is not really an issue. I just use my tap water to calibrate before every reading. It is very close to distilled.
Read the test, use the screw adjuster to get to 1.000 (brix?) then dry off the lens part and take your sample. It will make some difference but I have never had it off that far.

I used this calculator: http://www.brewunited.com/dilution_boiloff_calculator.php It agrees with your preboil and OG so I think the measurement at 15 minutes was faulty.

 

[stella_tigre]

The small amount of wort that you are sampling will cool to ambient in just a minute or so. So, temperature is not really an issue. I just use my tap water to calibrate before every reading. It is very close to distilled.

I thought the temp should not matter as you say, but after some confusing readings I've been testing using both hydrometer and refractometer. Unless the wort is cooled to around 80 degrees, it reads high. The error gets less as the bulk of the wort cools, until it agrees with the hydrometer reading. Don't understand why. And we have RO water, so I continually check calibration, as that changes as the temp of the refractometer changes.

 

[Brewmasher]

The ATC adjusts to the temp of the refractometer, not the wort. This is different than a hydrometer that gets adjusted to the temp of the wort. Granted the thin layer of wort will quickly match that of the instrument, but the instrument itself may be adjusting to changing tempratures. If you are brewing outside on a hot summer day, and bring your refractometer out of your air conditioned house, your readings will vary until the instrument stabilizes to the ambient temperature.

If you are outside in the sun, or your refractometer is near a heat source, a few drops of hot wort may set it over the ATC limit, if it is not already. A couple of drops of 200F wort can change the instrument's temp quite a bit.

Most refractometers are calibrated at 68F (20C). Allowing the sample and the instrument to stabilize as close as you can to that temp will give the best results, as will just using a hydrometer.

Wait for the temp of the instrument to stabilize if moved from a different environment, and calibrate with water that is about the same temp as your not too hot wort, and you should be fine. I just make a mental note of any difference and adjust on the fly instead of messing with that tiny screw adjustment. I just use tap water too. After all, the device is to make easier and faster readings so you can take more of them without much waste. If you require dead nuts accuracy, use a hydrometer.

 

[kh54s10]

The ATC adjusts to the temp of the refractometer, not the wort. This is different than a hydrometer that gets adjusted to the temp of the wort. Granted the thin layer of wort will quickly match that of the instrument, but the instrument itself may be adjusting to changing tempratures. If you are brewing outside on a hot summer day, and bring your refractometer out of your air conditioned house, your readings will vary until the instrument stabilizes to the ambient temperature.

If you are outside in the sun, or your refractometer is near a heat source, a few drops of hot wort may set it over the ATC limit, if it is not already. A couple of drops of 200F wort can change the instrument's temp quite a bit.

Most refractometers are calibrated at 68F (20C). Allowing the sample and the instrument to stabilize as close as you can to that temp will give the best results, as will just using a hydrometer.

Wait for the temp of the instrument to stabilize if moved from a different environment, and calibrate with water that is about the same temp as your not too hot wort, and you should be fine. I just make a mental note of any difference and adjust on the fly instead of messing with that tiny screw adjustment. I just use tap water too. After all, the device is to make easier and faster readings so you can take more of them without much waste. If you require dead nuts accuracy, use a hydrometer.

My hydrometer must always be within its calibration range. When I take a reading and look right away I can see it changing as the drop of wort cools. It usually only changes 1 or 2 points. It doesn't seem to be any different on my brew porch in the winter when it is near 32 degrees or mid summer when it could be over 100 while brewing. I have checked with the hydrometer and it is accurate.

I check with water before each reading. A lot of times it is right on and stays there for the session. Other times it will be a few points above or below 1.000. So I either have to reset it (sometimes for each reading during the session) or just wonder whether my OG might be 1.046 or 1.040, the range could easily be that far.

 

[Brewmasher]

My hydrometer must always be within its calibration range. When I take a reading and look right away I can see it changing as the drop of wort cools. It usually only changes 1 or 2 points. It doesn't seem to be any different on my brew porch in the winter when it is near 32 degrees or mid summer when it could be over 100 while brewing. I have checked with the hydrometer and it is accurate.

I check with water before each reading. A lot of times it is right on and stays there for the session. Other times it will be a few points above or below 1.000. So I either have to reset it (sometimes for each reading during the session) or just wonder whether my OG might be 1.046 or 1.040, the range could easily be that far.

You mean "My refractometer must be within its calibration range, right?

Does it have ATC?

 

[kh54s10]

You mean "My refractometer must be within its calibration range, right?

Does it have ATC?

OOPS! yes I meant refractometer. And yes it does have ATC.

 

[TheBrewBrotha]

I've purchased a new refractometer to test OG (starters and post boil wort). Some odd reason I can calibrate w/ distilled water but soon as wort touches it the scale goes completely white. This happens with hot and wort chilled to 70°F. Only used a drop of each hot and cold samples but as soon as i clean and drop distilled the blue side comes up. Tried playing with the calibration screw with wort samples and nothing, still all white reading

Anyone had this issue before?

 

[Brewmasher]

Maybe your wort is over 1.120?

 

[petrolSpice]

How are you cooling it? If you blow on it you will actually evaporate the water and leave the sugar, artificially raising the gravity. If you don't blow on it but wait too long it may do the same thing.

You don't need to pre-cool it. Just put a drop on it, close it so it wont evaporate, and let is cool for 15 seconds (or less, doesn't take very long to cool a single drop) and take a reading. Most refractometers will automatically correct for temperature too.

 

[govner1]

Better yet, if you're using a pipettes dip the bulb in cold/cool water to cool it first.

 

[TheBrewBrotha]

Lol that is a strong possibility. Definitely can't rule that out just yet. Just odd that I've been using the same 1:10 ratio

 

[TheBrewBrotha]

How are you cooling it? If you blow on it you will actually evaporate the water and leave the sugar, artificially raising the gravity. If you don't blow on it but wait too long it may do the same thing.

You don't need to pre-cool it. Just put a drop on it, close it so it wont evaporate, and let is cool for 15 seconds (or less, doesn't take very long to cool a single drop) and take a reading. Most refractometers will automatically correct for temperature too.

I was cooling my starter with an ice bath. First i tried a sample not cooled and get the all white reading. Thought maybe too hot and this is without blowing and letting it sit for about 20 secs. Tried while cooling at both 80 and 70f and still the all white reading

 

[arnobg]

Just to note too, you should be using more than a drop. To get an accurate and stable reading, the entire surface/lens should be covered with solution when putting the cover down.

 

[TheBrewBrotha]

Just to note too, you should be using more than a drop. To get an accurate and stable reading, the entire surface/lens should be covered with solution when putting the cover down.

Definitely made sure of that. Took about 2-3 drops to do so and I dragged the sample with the pipette to ensure the entire surface was covered