refractometer calibration fluid preservation

[salty joe]

We all know that calibration fluid for refractometers can go bad, presumably due to evaporation.

So I thought, why not store the calibration fluid inside a tightly capped larger jar that has a bit of water in it? The humidity inside the jar would be 100% so there would be no evaporation loss from the calibration fluid.

While every dollar counts, 60 ml of calibration fluid only cost $10 so this is more of a convenience thing. I've had my current fluid for a few years and no longer trust it and have to wait a week or so for a new bottle.

 

[PghReef]

I like to keep 2 or 3 bottles just for this purpose. Buy them at different times and as I buy a new one throw the oldest out. That way I can check my refractometer with 2 separate solutions and make sure they both read equal.
Bought my last one off amazon and it was reading at 1.029 instead of 1.026. Both my old ones read correct and I had a lfs test there water before making my purchase of a fish and tested the water from the bag when I got home, read dead on. Newest bottle was the bad one so age isnt everything. I'll stick to my brs solution and not use amazon again.

 

[Crabs McJones]

Curious as well. I had a bottle that was about 3(ish) years old, and it was getting low. Bought a new bottle, and come to find out my old bottle was giving me 1.030 instead of 1.026

 

[GabeM]

How does the fluid go bad from evaporation in a watertight bottle?

 

[Randy Holmes-Farley Verified Community Expert]

We all know that calibration fluid for refractometers can go bad, presumably due to evaporation.

So I thought, why not store the calibration fluid inside a tightly capped larger jar that has a bit of water in it? The humidity inside the jar would be 100% so there would be no evaporation loss from the calibration fluid.

While every dollar counts, 60 ml of calibration fluid only cost $10 so this is more of a convenience thing. I've had my current fluid for a few years and no longer trust it and have to wait a week or so for a new bottle.

I don’t know if leakage of water From a closed container is significant compared to when it is open,even if only open 0.01% of the time.

As a matter of scientific curiosity, exact 100% humidity is not perfect. Moisture will condense into the salt water, diluting it. Saturated salt water solutions are actually a good way to make controlled humidity air at less than 100%.

 

[salty joe]

I never would have thought the solution could become diluted-thanks.
My solution has been open maybe 0.0004% of the time-maybe 10 seconds a month. It'll be interesting to see how it compares to a new bottle of Brightwell solution.

How does the fluid go bad from evaporation in a watertight bottle?

I guess because nothing is perfect and a certain amount of water is lost, even when tightly capped.

 

[Randy Holmes-Farley Verified Community Expert]

I never would have thought the solution could become diluted-thanks.
My solution has been open maybe 0.0004% of the time-maybe 10 seconds a month. It'll be interesting to see how it compares to a new bottle of Brightwell solution.

I guess because nothing is perfect and a certain amount of water is lost, even when tightly capped.

comparing them To assess evaporation also assumes they were made perfectly to begin with! lol

 

[salty joe]

why not store the calibration fluid inside a tightly capped larger jar that has a bit of water in it? The humidity inside the jar would be 100% so there would be no evaporation loss from the calibration fluid.

Moisture will condense into the salt water, diluting it.

What if instead of fresh water, 35ppt water was used?

My current calibration fluid is from Aqua Craft Products. The calibration fluid on the way is from Brightwell Aquatics. Does either company have a reputation for their calibration fluid?

 

[Dr. Dendrostein]

We all know that calibration fluid for refractometers can go bad, presumably due to evaporation.

So I thought, why not store the calibration fluid inside a tightly capped larger jar that has a bit of water in it? The humidity inside the jar would be 100% so there would be no evaporation loss from the calibration fluid.

While every dollar counts, 60 ml of calibration fluid only cost $10 so this is more of a convenience thing. I've had my current fluid for a few years and no longer trust it and have to wait a week or so for a new bottle.

I bought the smallest containers of calibration fluid, store in fridge, still good after 6months. No loss of fluid

 

[Quietman]

Wonder if there's a cumulative effect of the bottle being open, leaving the cap off (happens to all of us occasionally) and having a half empty or more bottle over years.

A half empty (or less than 100% full) bottle would allow evaporation to maximum humidity in the bottle, not sure if that's 100% or not but it's likely higher than household. So over time this could become significant.

Probably not a bad practice to replace after year or two and more frequent if bottle has heavy use and is less full.

I would also doubt that moving to a new jar is going to improve this as you'll have same effect if that jar is routinely accessed.

 

[Randy Holmes-Farley Verified Community Expert]

What if instead of fresh water, 35ppt water was used?

My current calibration fluid is from Aqua Craft Products. The calibration fluid on the way is from Brightwell Aquatics. Does either company have a reputation for their calibration fluid?

sounds like a pain but will stop the tiny bit of water escaping the container.