Refractometer calibration solutions

JCOLE · Jul 14, 2019

I use this one. Dead on at 35ppt out the bottle. Seems to be good so far and reasonably priced.

Aqua Craft Standard Seawater 35 ppt Refractometer Calibration Solution - 60 ml https://www.amazon.com/dp/B0053DSWJA/ref=cm_sw_r_cp_apa_i_Eo3kDb7KQV5CK

Randy Holmes-Farley · Jul 14, 2019

Ohashimz said:
Randy which 35ppt solution tou recommend? Woild be nice to know if you have a preference..

If you have a good scale, I'd trust a DIY first. I don't have experience with testing the commercial standards, so go to a company that you otherwise trust.

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-06/rhf/index.htm

NOTE: THIS IS FOR A REFRACTOMETER ONLY:
This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water. That amount roughly corresponds to ¼ cup (73.1 g) of Morton's Iodized Salt dissolved into 2 liters (2000 g) of water (giving very slightly more than 2 L of total volume).

road_runner · Jul 14, 2019

Randy Holmes-Farley said:
If you have a good scale, I'd trust a DIY first. I don't have experience with testing the commercial standards, so go to a company that you otherwise trust.

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-06/rhf/index.htm

NOTE: THIS IS FOR A REFRACTOMETER ONLY:
This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water. That amount roughly corresponds to ¼ cup (73.1 g) of Morton's Iodized Salt dissolved into 2 liters (2000 g) of water (giving very slightly more than 2 L of total volume).

Super helpful. I cannot thank you enough for what you have done to this industry..
Our respect and appreciation sir.

Randy Holmes-Farley · Jul 14, 2019

Ohashimz said:
Super helpful. I cannot thank you enough for what you have done to this industry..
Our respect and appreciation sir.

You're welcome and thanks.

Spar · Jul 14, 2019

Randy Holmes-Farley said:
If you have a good scale, I'd trust a DIY first.

Do you happen to have a scale brand/model that you trust? I need to use for Chloroquine Phosphate dosing anyway.

TheGreatWave · Jul 14, 2019

Randy Holmes-Farley said:
If you have a good scale, I'd trust a DIY first. I don't have experience with testing the commercial standards, so go to a company that you otherwise trust.

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-06/rhf/index.htm

NOTE: THIS IS FOR A REFRACTOMETER ONLY:
This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified fresh water. That amount roughly corresponds to ¼ cup (73.1 g) of Morton's Iodized Salt dissolved into 2 liters (2000 g) of water (giving very slightly more than 2 L of total volume).

Yep this seems to work, I have my trusty box of Windsor salt wrapped up in a bag with all the other reefing paraphernalia lol. Maybe I will try it again later on to verify things are working correctly. (I have the Milwaukee that calibrate with RODI.)

Spar · Jul 16, 2019

I started testing out my new Red Sea Refactometer and it is a piece of crap. It literally won't hold a calibration longer than a few minutes. Looking at recent reviews on Amazon it appears everyone else is experiencing the same thing. Must have been a quality change recently. According to one review Red Sea even responded confirming this was true.

So back to the drawing board on what the most reliable unit is. This is literally driving me nuts. 5 or 6 different devices all that give consistently different readings after calibrations.

TheGreatWave · Jul 16, 2019

I like the Milwaukee unit as it is easy to use and takes some of the human variability out of it.

Tonight I mixed up 2 Liters of 000 water with 73.1 grams of Windsor's salt. I went with the full 2 liters as it would be most accurate, as it was the scale settled out at 73.3 after i put the salt away lol.

I zeroed out the machine with some 000 water and then performed the test. It reads 35 psu as expected.

The caveat is that this unit has a accuracy of +/- 002 salinity which doesn't sound that great but in reality seems to hold tight. It's possible that both my particular brand of salt and tester are out by the same amount, however that seems unlikely.

The only real maintenance I do is to give the glass a rinse off and a pat with a towel when I'm done to keep salt from accumulating on the glass.

vetteguy53081 · Jul 16, 2019

I use Milwaukee solution

Water Dog · Jul 16, 2019

vetteguy53081 said:
I use Milwaukee solution

You you have a link as to where you can buy some? I’d like to buy more for my Milwaukee digital refractometer.

madweazl · Jul 16, 2019

This has worked well for me the last three years. I double checked it against Randy's DIY recipe once and it's been very close with the four ICPs I've had done.

Spar · Jul 16, 2019

I have the same Milwaukee MA887. I hadn't calibrated it (at 0 ppt) in a long while, so did that. I tested it with 'Aqua Craft Standard Seawater 35 ppt Refractometer Calibration Solution' and also on water made using Randy's method. Both came within 1 ppt of each other (35-36 ppt). I then tested my tank water and it read 35 ppt. I think this combo is what I am going with in the future.

danged good thing I went through this testing of the self made salt water, etc. If I had trusted my new Red Sea Refractometer then I would have raised my salinity another 2-3 ppt, which would be way too high. Already got it boxed up for return.

saltyhog · Jul 16, 2019

I have not had any issues with the standard changing over time. My issue with the commercial standards if the varying from bottle to bottle. Often as much as 0.001 . Gonna make on going forward.

Spar · Jul 16, 2019

madweazl said:
This has worked well for me the last three years. I double checked it against Randy's DIY recipe once and it's been very close with the four ICPs I've had done.

Yep, just replied same time as your message, I like this bottle since very little is exposed to air when opened (just a prick at top). I'm getting rid of everything else I have and sticking with that brand + my MA887.

Spar · Jul 16, 2019

Water Dog said:
You you have a link as to where you can buy some? I’d like to buy more for my Milwaukee digital refractometer.

If you have the same MA887 then it calibrates with 0 ppt only as far as I can tell.

Water Dog · Jul 16, 2019

Spar said:
If you have the same MA887 then it calibrates with 0 ppt only as far as I can tell.

Yeah, since my last post, I just checked the salinity of my tank with the MA887. Tank reads 1.026 sg and then I rinsed off the eye with RODI, I took a reading of the last RODI rinse and it read a perfect 1.000 sg!