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Glass Hydrometer: Blown, Weighted with Shot, Calibrated in Known Liquids
A hydrometer is a glass float with a thin stem: it sinks deeper in light liquids and rides higher in dense ones, so a scale on the stem reads specific gravity. Baumé fixed his scale at two points, pure water and 15 % brine (Ure, 1839); here the scale is marked in sugar solutions of known strength, giving degrees Brix, and in liquids weighed for their specific gravity.
The picture: an old glass hydrometer with a paper scale inside its stem and a ballast bulb below.
Advanced
A day
Instructions
1
1
Blow the float
Blow the float
On a tube, blow an elongated bulb, then a small second bulb below it for ballast, and draw the tube above into a thin, even stem.
Materials for this step:
Glass Tubing Kit1 pieceTools needed:
Bench Glassblowing Torch
Safety Glasses
Heat-Resistant Gloves2
2
Ballast and scale paper
Ballast and scale paper
Drop small lead shot into the lower bulb until the float stands upright in water with most of the stem out. Slide a paper strip into the stem.
Materials for this step:
Lead Ingot50 g
Paper1 pieceTools needed:
Balance Scale3
3
Seal the top
Seal the top
Heat the top of the stem and draw it closed. Check that it floats upright and does not leak.
Tools needed:
Bench Glassblowing TorchSafety Glasses4
4
Mark the water point
Mark the water point
Float it in water at room temperature in the cylinder and mark where the surface cuts the stem: specific gravity 1.000 and 0 °Brix.
Materials for this step:
Water1 literTools needed:
Graduated Cylinder
Thermometer
Diamond Scriber5
5
Mark the other points
Mark the other points
Make sugar solutions by weight (see the notebook) and salt brines; float the hydrometer in each and mark the stem. Weigh 100 mL of each liquid to write its specific gravity beside the mark. Copy the marks onto the paper strip in ink and reseal if you opened it.
Materials for this step:
White Sugar0.3 kg
Salt0.3 kgWater2 liters
Iron Gall Ink2 mlTools needed:
Balance ScaleGraduated Cylinder
Quill Pen6
6
Calibration liquids
Calibration liquids
Loading Jupyter Notebook...
7
7
Limits
Limits
Ure's two-point Baumé principle and the Brix definition are sourced; the bulb form, shot ballast and weighing method are ours. Read at the temperature you calibrated at; this hydrometer has no potential-alcohol scale.
Materials
7- 1 piecePlaceholder
- 50 gPlaceholder
- 1 piecePlaceholder
- 3 litersPlaceholder
- 0.3 kgPlaceholder
- 0.3 kgPlaceholder
- 2 mlPlaceholder
Tools Required
8- Placeholder
- Placeholder
- Placeholder
- Placeholder
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