How do you calibrate a refractometer

[Paolissimo]

Hi guys
I purchased a used refractometer, the person that sold it to me (a fellow reef enthusiast) told me it's already calibrate it, and in fact show the right salinity in my established tanks. How would I go about calibrating perfectly? I google it and I really didn't understand how to calibrate it. I dont know anybody that has an established tank and I know I can go to the local fish store and sample their water, I was just curious how you guys calibrate it.
Thank you.

 

[rkaragozler]

their is 2 ways to go about it
1 using your ro/di water put 2-3 drops and the glass and then adjust the screw till it reads dead zero.
2-get calibration fluid and do the same.

 

[Reef Reaper]

+1

 

[Paolissimo]

Thanks I will do both.