Where we are at now... and some tips...
...is the fun stage - just playing with some old 0-100 hydro's, until our competent equipment arrives.
During this play stage, here's some tips...
1. Pour the rum into the cylinder by tipping the cylinder and slowly pouring the rum down the sides, to prevent splashing and the formation of bubbles. Let the rum stabilize for perhaps 10 minutes insofar as both temperature and bubbles.
2. If you are using an ordinary glass thermometer, take your time as it too needs to stabilize. Hold it by the tip top to avoid heat transfer from your 98 deg F hands. Far better, you can find nice digital probe thermometers that are instant read, with no need to stabilize (not to mention they are accurate to 0.1 degree). How much? Just $3 to $8 or so is fine.
This Insten is just fine, and $3 at Walmart. I use my grilling electronic/digital probe.
3. Stuff your pride and use a
magnifying glass to read (duh) your hydro and/or glass thermo. Don't be like me and take readings without wearing your glasses. Me idiot.
4. When inserting the hydro, do it slowly (save rapid insertion for your mistress). Before letting go, give it a spin to release any bubbles clinging to the hydro (and causing error).
Flat Ass Bottom Line
Believe me - you saw me do it - its easy to rush, and make little or even big errors. A difference of just one degree (easy to do with a glass thermo) leads to a difference of 2g in sugar, not to mention misreading of your hydro. Fortunately, as long as you are aware of the need to just slow down a bit, and get decently accurate readings, the method itself is foolproof and really quite accurate.
This is exactly why I'm recommending you buy 10 point hydros (per Johnny) as they are absolutely the most accurate and easiest to read, and yes, still very inexpensive. Just buying the 30-40 and 40-50 will cover 95% of the rums you have.
If you are desperate to test an OP, just buy the kit (0-40, 40-70, 70-100) for just another $7 but use the 10 point hydros wherever possible. For the moment OP's are so few as to be irrelevant for now.
Have fun, and keep inserting, but slooooowly...