My Refractometer is acting weird...

[OswaldvW]

The past few half a dozen brews I have been noticing some strange things with my refractometer.

I check my pre-boil gravity, and say take a reading of 1.043. After boiling for 60 minutes, I check my starting gravity and get...... yes, 1.043. What?

Now, I will have you know I do the following:

1.) make sure I thoroughly stir my pre-boil wort before taking a sample
2.) make sure the plate on refractometer is perfectly clean AND dry. No water to dilute reading
3.) allow refractometer to sit for a few minutes for wort to reach room temperature.
4.) For what it's worth, I brew using a Grainfather, and I achieve good rolling boils that "burns off" a gallon or so of water per hour of boil.
5.) I make sure my refractometer is calibrated. However, even if it wasn't, shouldn't I get a higher reading post-boil than pre-boil?

This is really frustrating as either I am getting bad pre-boil gravity readings or bad post-boil gravity readings.

Any suggestions would be greatly appreciated. Also, if anyone has experienced something similar to this with their refractometer, I would be interested in hearing from you.

Thanks!

 

[morbster]

I'll ask the obvious: do you have a hydrometer to compare against?

 

[OswaldvW]

yes, I have been relying on my hydrometer just to get accurate readings, usually just my post-boil readings.

The PIA is with the pre-boil. It takes time for the sample to cool down to readable temperatures.

 

[IslandLizard]

What gravities did you expect pre-boil and past boil (OG)?

I agree, use a hydrometer when in doubt, but let the wort cool (close) to its calibration temp.
Take a thick glass from the freezer to cool the sample down quickly.

Evaporation of hot samples between taking and reading will make exact gravity measurements on a refractometer impossible, but they may be close enough for practical purposes.

 

[doug293cz]

I think IslandLizard might be on to something with the evaporation from the sample. I suggest taking the sample with an eyedropper, and letting the sample cool in the dropper prior to placing on the refractometer. You can even put you finger over the opening of the eyedropper to eliminate any possible evaporation from the tip.

Brew on

 

[Revvy]

Do you calibrate your refractometer before every session? I keep a tiny test tube of R.O. water in my refractometer pouch, and the first thing I do is zero it out with the distilled water.

 

[brick_haus]

I find that my refractometers calibration changes with the ambient temperature. I calibrate early in the morning when it is cold, then later in the day, when it warms up, the calibration is off and I need to recalibrate.
So...I calibrate it before every single use. Just takes a second to be sure that I get reliable results.

 

[IslandLizard]

Just thought of this.
Is that refractometer for sugar? Not saline or something else?

 

[OswaldvW]

OK. Today I am brewing a Flanders style Red. A little bold and big, so my pre-boil is:

1.055/1.056

If all goes according to plan, should have a post boil around 1.063. Will see what happens.

 

[Phingertoes04]

I'm kinda having the same issue... my plan is to use a hydro and my refractometer on my next brew to compare the two.

first time dealing with a refractometer so lucky i found this:rockin:

 

[OswaldvW]

Well, the pre-boil gravity on the hydrometer came out at 1.052, so I am going to have to make sure I totally calibrate my refractometer all over again. Post boil was 1.060. (Also measured with the hydrometer. I just gave up on the refractometer during yesterday's brew session.

I kept checking the gravity in the first 20 minutes of boil (120 minute total boil time) and got 1.054, 1.063, and 1.058.

 

[kh54s10]

I calibrate my refractometer several times during brew day. I just use tap water most of the time figuring it is close enough for my purposes. I also wet the lens, look for the reading and look again in a minute or two. If it changed I wait a bit longer then look again. It usually stabilizes in a couple of minutes. Sometimes I get a reading that I don't think is accurate, so I take another, occasionally I take a third and if 2 of them were the same I used that number.

If you get the same number preboil and post boil, one of the readings is wrong. Backup is the hydrometer. I have never had to resort to the hydrometer before measuring for FG since I got my refractometer about 5 years ago.

 

[OswaldvW]

If you get the same number preboil and post boil, one of the readings is wrong. Backup is the hydrometer.

Yes, hence the reason for this post. One could even argue that both readings are possibly incorrect.

I have been doing readings on my hydrometer as well. What is infuriating about this is I have been using my refractometer for years and never had a problem, and all of a sudden this spring and summer I am getting bizarre readings.

 

[IslandLizard]

Yes, hence the reason for this post. One could even argue that both readings are possibly incorrect.

I have been doing readings on my hydrometer as well. What is infuriating about this is I have been using my refractometer for years and never had a problem, and all of a sudden this spring and summer I am getting bizarre readings.

My best guess is, it's simply broken!

Use a (calibrated) hydrometer instead.

 

[OswaldvW]

Got a new refractometer and there was more than a 10 point difference between the two at my most recent brew session.

 

[Qhrumphf]

Tip for chilling hydrometer samples, have a vessel of super cold (near freezing) water, and collect your sample in a metal cup. Use cup like ice bath, and swirl. I use it for both pH samples and hydrometer samples throughout.

In addition to the the refractometer lense, make sure there's no residual liquid in your pipette that could contaminate your sample. I've found that throwing off refractometer readings easily, especially if you switch from mash/first runnings (very high gravity) to late sparge runnings (very low gravity) to preboil (somewhere in between). A couple drops of first runnings can easily make last runnings seem high, or make last runnings (especially if running a highly efficient brewhouse and running right up to the danger zone) could easily dilute your preboil reading.

 

[2005STi]

I would recommend being sure the refractometer sample is cool before testing. I've had the same problem as you and noticed when I went back to my tablespoon sized sample after 20 minutes or so, my reading was about 8 points higher and reflective of my usual boil off.

 

[Mothman]

I've used my refractometer for only two brews.

The first was on a friends extract batch, just to try it out... and the same issue arose as the OP... the pre-boil gravity reading was the same as post-boil (and matched the predicted post-boil).

I then used it on my first all-grain attempts, and there the pre-boil and post-boil readings both made sense and seemed correct (post-boil verified with a hydrometer)

I took it to be an indicator of the extract batch not being adequately mixed before boil, despite what we thought was some pretty thorough stirring.