Just ordered one. Hopefully will have this hydrometer calibrated by Friday.It doesn't surprise me that there are slight differences among calibration fluids, after all practically everything has a standard error (everything mass produced)... the best an average Joe can do is compare as many replicates as possible and accept the most common as being closest to correct...with that said, why not just get a precise scale with really good reviews off Amazon because his scale is unlikely to match yours perfectly even if it's the exact same model