Refractometer Problems

[traviswalken]

I am getting inconsistent readings on my ATC refractometer. On my last brew day, I put hot wort on the refractometer and checked the gravity. I then let the refractometer sit for about 1 minute and checked it again. My gravity changed significantly. IIRC, it went from about 1.047 to 1.053.

I have had similar trouble with the refractometer in the past, but this was the first time I have brewed outside on a cold day. I think it just magnified the problem. It has also been VERY difficult to read at times due to the blue line being fuzzy.

So am I doing something wrong? Is hot wort on the refractometer a no-no? I checked the receipt, and it is an ATC refractometer (I assume it stands for automatic temperature correction).

Do I need a new refractometer?

Thanks.

 

[arcaniment]

I may be wrong, but the change in gravity may have been the refractometer adjusting to the correct temperature. You are correct, ATC is temperature correction, and I believe you have to let the sample sit on the lens for a bit to correct.

 

[30Bones]

Same issue here brewing in the cold garage. Next time I will let the sample sit a bit and check it a few times.

 

[ResumeMan]

+1 - the way the ATC corrects temperature is simply that the glass prism is a much bigger mass than the little drop of liquid you put on it, so it normalizes the temperature very quickly...like in less than a minute. So the ATC is not instantaneous, and the second reading is what you should be looking at.

Now one thing I do not know is whether the reading will be thrown off at low ambient (and therefore presumably low prism) temperatures.

BTW, the refractometer eyepiece should have a twisty end that you should be able to use to dial in the focus, doesn't it? Kinda like binoculars?

 

[mooshimanx]

Leave the refractometer in your house if the garage is very cold. Put the drops of wort onto the prism and then let it adjust for a few minutes before taking a reading. Refractometers like the hand-held wine/brewing ones don't actually "correct" anything, they just have use a very small amount of liquid so the drops reach the temperature of the prism very quickly when in contact with it. But its still not instantaneous.

 

[traviswalken]

Thanks for the help guys. I will use smaller amounts of liquid, keep the refractometer at "normal" temps, and give it a minute or two to stabilize.

 

[traviswalken]

BTW, the refractometer eyepiece should have a twisty end that you should be able to use to dial in the focus, doesn't it? Kinda like binoculars?

I can get the numbers in focus, but the blue line isn't effected by the focus. It is an intermittent problem. Sometimes the blue line is totally crisp, sometimes I am just estimating the og because the line is so blurry. I haven't figured out the common denominator. Based on this thread, I would guess it is user error. Maybe using less liquid will help???

 

[Cathedral]

I work with refractometers constantly measuring coolant at work. The two biggest reasons you will see a fuzzy line instead of a crisp line is a) there's too much oil in your coolant! [not likely the problem here] or b) your prism has dirt or oil from your fingers on it. The amount needed to get it dirty is ridiculously small; you should always keep a microfiber cloth with the refrac and wipe the prism just before use.

Keep it warm, clean, and calibrated and you shouldn't ever have a problem.

 

[Cathedral]

Also, I know it seems obvious, but don't forget to clean the little plastic flap as well... since it comes in direct contact with the prism.