About Bottle Fill Level, Weight vs Volume Measurements, and Headspace
Culinary Solvent is pure ethanol sold in pints, quarts, 5 gallon jugs, and 55 gallon drums. Depending on your bottle size, there may be some headspace present making the bottle look like it wasn't filled all of the way. Some customers have weighed their bottle of Culinary Solvent in an effort to see how much liquid is contained in the bottle, and the results of such a measure can often cause confusion.
This blog post is intended to clarify how we fill, how much is contained in each bottle, the purpose of the headspace in the bottle, and provide more information on why a 32 fluid-ounce bottle weighs less than 32 ounces when placed on a kitchen scale.
How are bottles of Culinary Solvent filled?
We use a "4-head bottle filler" at the distillery which allows us to fill four bottles at one time. Our filler is calibrated each bottling run to ensure an accurate and consistent fill throughout the run. In addition to calibration, each bottling run has a "fill test" performed at the beginning, middle, and end of the run to ensure consistency throughout the process.
Why does my 32 fluid-ounce bottle weigh less than 32 ounces?
The answer comes down to density of the liquid inside the bottle, coupled with some natural confusion presented when using the word "ounces" to measure both volume and weight. This confusion is eliminated when measuring in metric, where grams denote weight (actually mass), and liters denote volume.
Density is the measurement of a material's weight compared to the volume it displaces. The density of water is 1.00 g/ml (grams per milliliter). This measurement for water is equivalent to 0.9587 oz/fl-oz (ounces per fluid ounce).
However, the density of 200 proof ethanol is less than water, measuring in at just 0.789 g/ml, or 0.823 oz/fl-oz. This difference in density is the reason why a 32 fluid ounce bottle of ethanol weighs less than a 32 fluid ounce bottle of water.
How much does a 32 fluid-ounce bottle of Culinary Solvent weigh?
Using the numbers presented, the contents of one 32 fluid-ounce bottle of ethanol (with a density of 0.823 oz/fl-oz) should weigh approximately 26.34 ounces on a scale. The average weight of an empty bottle and cap comes in at about 2.5 ounces, pushing the total weight of an unopened 32 fluid ounce bottle to about 28.8 ounces.
Filling Bottles by Weight not Volume - Metric vs Imperial
Because of the confusion created when measuring ounces for volume and for weight, we calibrate our bottling system and testing procedures to measure our ethanol using grams. Bottles are filled and tested for accuracy by weight in grams to ensure consistent dispensing throughout the bottling run. Measuring the grams dispensed into each bottle also ensures that consistency is met regardless of the temperature of the ethanol on bottling day.
Using the density presented above for ethanol in g/ml, one 32 fluid ounce bottle of Culinary Solvent will contain 746 grams of 200 proof ethanol. An average empty bottle and cap will add another 77 grams to the bottle. The allowable tolerance for our bottle filling system is +/- 1% of 746 grams which amounts to 8ml or 1.5 teaspoons of total liquid per quart bottle.
What's the purpose of the headspace in my bottle of Culinary Solvent?
Bottles and jugs of Culinary Solvent ship with an adequate amount of headspace to allow for thermal expansion of the liquid contained without compromising the leak-proof integrity of the bottle. This headspace of air compresses or expands in relation to the change in volume of the ethanol as the temperature changes throughout delivery and storage.
Glass bulb thermometers are a great example of the thermal expansion that is possible with ethanol temperature changes. The red liquid contained in the bulb and stem of the thermometer is ethanol, which replaced the much older-fashioned silver mercury thermometers. Even small changes in temperature will affect the overall volume of the liquid which is indicated by moving the liquid's level up or down the stem.
In order to provide adequate headspace, Culinary Solvent bottles are bigger than the volume being sold and shipped. Specifically 32 fl-oz bottles will hold 33.6 fl ounces if filled to the top, while 16 fl-oz bottles will hold 17.5 ounces. This extra space is designed into the packaging on purpose to permit the expansion of the liquid without compromising the leak-proof seal of the cap.