Refractometer Issue

Cole_Voeller · Feb 8, 2023

Hello all,
Weird question. So basically, I’ve always used a bottle of Fritz Refractometer fluid to calibrate my refractometer. I had a bottle of BRS fluid, and also just got another brand new one. Well today I tried all of them, to find there was a difference of 5ppt between the Fritz and a BRS bottle, and 2ppt between the two BRS bottles. So yikes. I tried setting my Refractometer to zero using RODI, and tested the three bottles; Fritz was 39, and the BRS were 34 and 36ppt. How can I deduce which one is right? I’m worried that my salinity has been way off for a while and I’ve had no idea.

Saltyreef · Feb 8, 2023

Cole_Voeller said:
Hello all,
Weird question. So basically, I’ve always used a bottle of Fritz Refractometer fluid to calibrate my refractometer. I had a bottle of BRS fluid, and also just got another brand new one. Well today I tried all of them, to find there was a difference of 5ppt between the Fritz and a BRS bottle, and 2ppt between the two BRS bottles. So yikes. I tried setting my Refractometer to zero using RODI, and tested the three bottles; Fritz was 39, and the BRS were 34 and 36ppt. How can I deduce which one is right? I’m worried that my salinity has been way off for a while and I’ve had no idea.

Are you taking into account the temperature of the solution?
Normally you need to let it equalize with the sample dish for ATC to work properly.

Cole_Voeller · Feb 8, 2023

Saltyreef said:
Are you taking into account the temperature of the solution?
Normally you need to let it equalize with the sample dish for ATC to work properly.

Yes, All are same temp. All kept in exact same place

YOYOYOReefer · Feb 8, 2023

how old are the other 2 fluids,,most expire in 12 months or less plus . buffers can go bad.

at home i use extra vigin olive oil (we buy by the gallon so we always have it at home) as my baseline to test (71-72 Brix) just to make sure my buffers are still up to snuff.

Saltyreef · Feb 8, 2023

Cole_Voeller said:
Yes, All are same temp. All kept in exact same place

What kind of refractometer are you using?

Some brands are better than others.

Myself, i use a $30 glass hydrometer from tropic marin. Dead nuts accurate

X-37B · Feb 8, 2023

Saltyreef said:
What kind of refractometer are you using?

Some brands are better than others.

Myself, i use a $30 glass hydrometer from tropic marin. Dead nuts accurate

The simplest hydrometer to use.
I have several. All 3 read exactly the same so yea acurate!

Cole_Voeller · Feb 8, 2023

YOYOYOReefer said:
how old are the other 2 fluids,,most expire in 12 months or less plus . buffers can go bad.

at home i use extra vigin olive oil (we buy by the gallon so we always have it at home) as my baseline to test (71-72 Brix) just to make sure my buffers are still up to snuff.

Fritz is maybe 9 months old. BRS ones are both less than 4 months old.

Cole_Voeller · Feb 8, 2023

Saltyreef said:
What kind of refractometer are you using?

Some brands are better than others.

Myself, i use a $30 glass hydrometer from tropic marin. Dead nuts accurate

I use BRS refractometers. The refractometer isnt my issue however, its the calibration fluid I have.

X-37B · Feb 8, 2023

You can make your own. Do a search here as its easy to do.

gbroadbridge · Feb 8, 2023

Cole_Voeller said:
Hello all,
Weird question. So basically, I’ve always used a bottle of Fritz Refractometer fluid to calibrate my refractometer. I had a bottle of BRS fluid, and also just got another brand new one. Well today I tried all of them, to find there was a difference of 5ppt between the Fritz and a BRS bottle, and 2ppt between the two BRS bottles. So yikes. I tried setting my Refractometer to zero using RODI, and tested the three bottles; Fritz was 39, and the BRS were 34 and 36ppt. How can I deduce which one is right? I’m worried that my salinity has been way off for a while and I’ve had no idea.

Make your own calibration fluid.

Very simple. Mix 3.65g of table salt into 96.35 g of RODI water = 35ppt

edit: should mention that this is based on Mortons Iodized Salt.

Cole_Voeller · Feb 8, 2023

gbroadbridge said:
Make your own calibration fluid.

Very simple. Mix 3.65g of table salt into 96.35 g of RODI water = 35ppt

edit: should mention that this is based on Mortons Iodized Salt.

Might have to give that a go. Thank you!