Refractometer calibration solution

[TheHarold]

I guess if that's what the manufacturer says to do, that's what you should do, but even way back through high school and college chemistry classes I was always taught to calibrate instruments within the range of expected results. This is why calibration solution is 35ppt, and not 0.

You can certainly check using a 35ppt solution- I have that as well.

But refraction is pretty simple. Once you have a “zero” point, it’s a simple calculation from there.

 

[Randy Holmes-Farley Verified Community Expert]

Salt solutions for a refractometer can only go bad through evaporation, or by contamination.

 

[Crabs McJones]

Salt solutions for a refractometer can only go bad through evaporation, or by contamination.

Thanks randy. Had to be contamination somehow as I always close the lid tightly to help avoid this situation. Although it didnt work out so well this time ;Hilarious but thank you

 

[Westside Guy]

Well all I can say is that I have the Red Sea refractometer and I also have both calibration fluid at 35ppm and RODI
I’ve calibrated with both and it makes no difference in my case, so I tend to just use the RODI these days, not forgetting to wipe the glass plate with my shirt! Lol
I’m not arguing against the fluid, it’s good and fine to use it if people prefer.

I also have the Red Sea refractometer and the instructions say that you should just use RODI and calibrate to zero ppt. It makes no mention of using calibration solution so that is one additional expense I don't need to add to my reefing overhead.

 

[Randy Holmes-Farley Verified Community Expert]

I also have the Red Sea refractometer and the instructions say that you should just use RODI and calibrate to zero ppt. It makes no mention of using calibration solution so that is one additional expense I don't need to add to my reefing overhead.

Maybe.. It means you are trusting the device to be operating correctly. Using a calibration solution at or close to tank salinity eliminates that concern.

 

[rushbattle]

Maybe.. It means you are trusting the device to be operating correctly. Using a calibration solution at or close to tank salinity eliminates that concern.

This! Thanks for chiming in again Randy!

 

[OutsideBrian]

What’s the best way to calibrate a refractometer?

 

[rushbattle]

What’s the best way to calibrate a refractometer?

Second post in this thread.

 

[Randy Holmes-Farley Verified Community Expert]

What’s the best way to calibrate a refractometer?

Depends on the refractometer, but if it can be calibrated with a 35 ppt standard, that is never wrong and often better than any other way.

A few electronic models must calibrate with pure water, but then it’s a good idea to check them with a 35 ppt standard.

 

[OutsideBrian]

Second post in this thread.

I feel like I just got smacked in the face by Bill Nye
The reason I was asking was because I tried calibrating mine with Rodi per the instructions. When I did I was reading about 1.030 on my refractometer. I then adjusted my tank to the newly “calibrated” refractometer. I took a few gallons of tank water out a day and replaced with fresh rodi water.
Once I got it down to 1.025 I stuck a swing type measuring device in only to be shocked at it saying 1.020
I went to my LFS and tested some of their water and it read 1.029 on my refractometer.
Now I’ve come to realize COLD rodi water will not accurately calibrate since temperature is actually a factor according to that article.

 

[MnFish1]

Yes, this is very likely, even inevitable maybe. It’s why I really advocate Dr. RhF DIY refractometer solution. Just make a new batch every 4-6 months and keep it tightly sealed in the mean time. Prevents this issue all together. Glad you are getting it rectified.

Ironically, salinity is one of the most important parameters to measure effectively and monitor, but it is pretty difficult to measure by hobbyists. I found a smoking deal on a lab grade conductivity meter and probe. Bought a box of conductivity calibration solution packets. Set for a decade, it’s quite a relief.

I have used the individual packets with success...
http://www.reefkeeping.com/issues/2004-06/rhf/index.php

 

[rushbattle]

I feel like I just got smacked in the face by Bill Nye
The reason I was asking was because I tried calibrating mine with Rodi per the instructions. When I did I was reading about 1.030 on my refractometer. I then adjusted my tank to the newly “calibrated” refractometer. I took a few gallons of tank water out a day and replaced with fresh rodi water.
Once I got it down to 1.025 I stuck a swing type measuring device in only to be shocked at it saying 1.020
I went to my LFS and tested some of their water and it read 1.029 on my refractometer.
Now I’ve come to realize COLD rodi water will not accurately calibrate since temperature is actually a factor according to that article.

Cold or hot RODI is not a good idea. Reference solution at your target salinity won’t let you down unless you don’t let it sit on the refractometer to equalize temp.

Mixing the DIY solution is super easy, don’t worry about all of the information about why it works. Just look at the recipe. Randy made it really easy.

It’s also easy to just buy calibration packets if you don’t feel like mixing up his solution recipe.

 

[Fotocha]

I'm just curious (never owned one) anyone ever thought about just keeping a hydrometer to compare? I mean they're what $6???

 

[turfster26]

Salt solutions for a refractometer can only go bad through evaporation, or by contamination.

That's why I seal mine tight after every use and keep the little jar of solution in a ziplock bag, Mine has been spot on for years and I compare it to a second (newer) bottle I have that came with my GHL Profilux controller.

 

[Cory]

This is why i use a floating hydrometer (tropic marine) and a refractometer. One is quick the other is slow. One needs calibration and the other cant be. I trust my floating hydrometer more than all them. I also have a milwakee digital refractometer to tripple check lol. Oh and a swing arm. Guess what? They all read nearly the same. When you have more than 2 salt testing devices you know how crazy salinity can make you. Cant wait to get a conductivity meter.