Help me with my gravity readings

[hio3791]

Hard to see but here's a pic with 70F water, after correcting for temp, the hydrometer reads 1.000.

View attachment 1468068324280.jpg

So what the heck is going on with my pre and post boil readings? The pictures at top of thread were taking over an hour apart as I did a 90 min boil. The only thing plausible is that this hydrometer is inaccurate at some SG range.

Planning to pick up a refractometer in time for next brew.

 

[RevKev]

Hard to see but here's a pic with 70F water, after correcting for temp, the hydrometer reads 1.000.

View attachment 361415

So what the heck is going on with my pre and post boil readings? The pictures at top of thread were taking over an hour apart as I did a 90 min boil. The only thing plausible is that this hydrometer is inaccurate at some SG range.

Planning to pick up a refractometer in time for next brew.

Refractometer is smart, as long as it's calibrated with distilled water instead of tap water.

General rule all hydrometers are standardized yet not all standardized hydrometers are calibrated.

I'll attach a link to NISTs overview of hydrometer calibration but unless you paid 80$ for a hydrometer you are likely to receive results greater than ±0.001SG in the order of two or more magnitudes. A calibration report should note where and by how much the instrument varies so you can correct usually in several spots.

http://www.nist.gov/calibrations/upload/sp250-78.pdf

 

[Yeastieboy]

Removed....