Refractometer calibration at July meeting.
i just ordered a bottle of pinpoint salinity calibration juice. it set at 35 ppm the same as NSW. i just whipped up some DIY solution(RHF formula) and it told me that my refractometer was far enough off to order the good stuff. so my point is, that i will bring the pinpoint solution to the next meeting. If you want your refractometer calibrated to NSW values (35ppm-1.0264) just bring it by. I only have 1 2oz bottle. that should be more than enough to do everyone that has been showing up lately.

Josh, Great idea! When I received mine (group buy - MARS) it was only off by 1ppm Salinity. Easily adjusted with the included screwdriver. I also have a calibration bottle that I'd be happy to bring in should a deluge of meters show up. I really wanted one because I've had several float arms that all read differently. Right before I got the refractometer, I had two swing arms: one that read 1.024 and one that read 1.020. Of course, I was using the lower one; the wrong one. Upon receipt of the refractometer I discovered this error, tossed the lower reading one and found the higher one was only slightly off (read above). So honestly, I cheat. I use my float arm hydrometer 90% of the time that I have calibrated with the refractometer/cal solution. I know exactly how much the float arm is off by and simply adjust for that. Much quicker and easier than breaking the refractometer out of its home & box, filling the pipette with solution, dropping the appropriate amount on the refractometer while being very careful not to spill it, carefully close the lid so it evenly spreads the fluid across the glass, then walk over to a window to get the best light and view the reading. Then clean and maybe rinse off the surface, drain the pipette, put back in the box, put box in its home. Float: pick up, fill with water, tap for bubbles, read, rinse, repeat, put back. Love my refractometer but it has seldom been used.

I use dilltiled water to calibrate my refractometer. Thats what the directions said. :?

yeah, i do too. :? i saw a thread on RC about refractometers and apparently if you have one of the cheapo RHS-10-ATC units(blue and black handles), they can be accurate from the mfgr or up to 4 PPT off. according to the thread they are calibrated to a table salt slope and not to a seawater slope. i dont understand how exactly it works, but if RHF says that they can be way off similar to swingarm hydrometers then i tend to listen. my tank has been good as far as the #'s look but things just dont look right. i have a cheapo refractometer i only calibrate with water so maybe thats it. for 5$ a bottle its worth it to know for sure. the one thing i did learn is that when its calibrated to 35PPT its only accurate at 35PPT because of the slope of the prism. 35ppt just happens to have the same refractive index of the pinpoint solution. if you have a higher end unit then FW calibration is ok. this only pertains to the cheap chinese ones.

heres the thread http://reefcentral.com/forums/showthread.php?s=868e72c298e2380d68306ea956ac6b06&threadid=953605

Great info Josh! Thanks! I've always understood it's best to calibrate a device in the range within which you are expecting to read. Also makes sense to calibrate with a 35 ppm liquid when that's the easiest line to see on my refractometer. :D Also, based on the prizm slope as Josh said, the 35ppm is about in the middle of this device. I'm pretty sure I have the cheapo one for the price I paid. Nonetheless, a great way the club can provide increased reef aqaria knowledge to those interested!!! ;)

the Pinpoint 53Ms calibration solution (1.0264/35 PPT) showed up today and as far as it looks to me i was 3 ppt low on salinity basically i read 1.025 on my refractometer i was really at 1.022/32PPT ouch. i need to slowly bring up my salt. i filled my topoff with saltwater instead of fresh so that will help at 2-3 gals a day.