Yesterday, I went to the brew store, and spoke with the local concierge d’brew about the methods of making hometown root beer.  He was polite, and disdainful.

The great arts of liquor – brewing, winemaking and spirits – do not recognize the simple use of Saccharomyces for carbonation.  Yes, root beer and and soft spirits can be naturally carbonated – but why bother?

This, from an industry that has people making twenty-gallon lots of wort and mash and grape-stompings into home-made potables.

My first ferments, which produced hard root beer lager-style, were not too awful, but dry as a lemon.  They had fizz, but no head.  In reading the online literature, I found that maltodextran – polymerized maltose – is not digestible by yeast.  Some can take on maltotriose – but no better than that.  Maltodextran adds body to the liquid, and foam to the head.  So my recipe – in my head – called for back-adding 2 teaspoons of maltodextran per half-gallon of root beer.

Also, the yeasts do not make lactase, so lactose in unfermentable, although they can take on the remnants – glucose, and, I suppose, galactose – they are fairly skilled hexose fermenters.

I added about ½ cup of lactose to my “lo-test” rootbeer, and stirred it up.  The maltodextran went in at 1 tsp as well – there’s only a liter left in the bottle.  The “hi-test” rootbeer – which did not freeze, by the way, when put in the freezer – got 2 tsp of maltodextrin, but there was no room for lactose.  This one’s stalled out a bit earlier, and left some sweets in the bottle.  They are chilling.

I purchased a #6 drilled rubber stopper and a bubble trap, so that my growlers can be used to make root beer without blowing the whole mess to Kingdom Come, and all over the kitchen.  One can safely brew anything with an open system, to let the pressure go to the environment.  It may make for less carbonation, but is better than an explosion.

I bottled up a fresh batch of root beer in a brown growler, putting ½ ounce of sarsaparilla down on 1 cup of lactose and 2 ounces (dry) of cane sugar (sucrose), and ¼ tsp. of Red Star Cuvée Yeast.  Then, one covers with 1 tbsp. root beer extract (Fermentap extract) and 1 tsp. vanilla extract, and about a liter of spring water (bottled, no chlorine.)  Swirl it until the solids dissolve, and the liquid looks like Flint, Michigan tapwater.

Add a liter of distilled water – the yeast don’t need many salts, and they get them from the spring water.  I placed the bubble trap, and put it in the garage at 10°C.  The fermentation should go to completion, eating up all the cane sugar to give around 1.6 oz ethanol in 64 oz container, or about 2%, if that; while carbonating to about 1cm CO₂ head pressure.

I left it out overnight.  It seems to be in mid-fermentation this morning.  It’s putting out about 10μL/sec of bubbles (CO₂, of course) and has probably blown out the covering O2 from the bottle.  The cap drops about every 25 seconds or so, letting a 250μL bubble out – that’s all sheer handwaving, within an order of magnitude.

Given that air at atmospheric pressure is 44.6 mM  at STP (22.4 L/mole); and about 37.9 mM where I live, or 37.9 μmoles/mL, it’s bubbling at 9.5 μmoles of CO₂ per second, or 37.05 mmol/hour of CO₂.  That would mean eating up half that in sucrose (2 moles CO₂ per mole of sucrose.) 18.5 mmol/hr, or 6.34 grams of sucrose per hour.  Not much, I expect.  2 oz. dry sucrose is 70 grams.  That means that it should run to completion after about ten hours.

I might try it in a mild water bath.  Or not.

An utterly unverified quote from Sowell, Jeff. Consumer Affairs Specialist. Coca-Cola Company. Letter. 31 May 2000:
For example, the table shows a typical can of Coca-Cola classic with 3.7 volumes of carbon dioxide dissolved in the product at a temperature of 75F has an internal pressure of about 55 psi. (That’s 380 kPa)

Yeezis.  To gas-pressurize root beer:

  • Seal the keg and pressurize by setting your CO2 regulator to 25 pounds.
  • Refrigerate under pressure for 24 hours.
  • Reduce regulator pressure to 5 pounds.

That’s freaking terrifying.

Dispensing root beer means putting it at 5PSI over room pressure, or 351.5 cm. H2O.  I’m catching it at one (1) cm water.

A growler’s 5″ across, or 2.5″ in radius- call it 6.25 cm radius.  39.2 cm circumference.  6.5″ high (16.5 cm)  650 cm² surface area, with an atmosphere defined as 101.325 kPa, or 10.13 N/cm².  6500 Newton’s, let’s say, working on a glass growler at 1 atmosphere, 2200N at 5PSI.  The bottle’s being stretched outwards with a total force on the curved sheet of glass of 440 lbs.  No, thanks.

I see that beer at 4 bar and 25 °C has a carbonation level of 7.5 g/l (link)  For BEER, that means that  [1 bar = 100,000 Pa]  One bar approximates room pressure.  30 grams of CO2 in beer produces 4 bar head pressure.  The head pressure should be relatively proportionate to the contents.

One growler distributor offered:

it was discovered that the last bottle production shipped to Village may contain defective growlers that do not meet the minimum internal pressure of 75 psi

That’s five bar. I don’t like that. That would put the pressure on the cap (about 1 square inch) at 75 lbs.

In the physics and chemistry of any gas solution, there will be a partition across the vapor phase and the condensed (host liquid) phase.  CO₂ will remain free in a CO₂/H₂O/air mixture above a liquid, and within as a CO₂/H₂O/air solution in the water.

To go full geek, I reference The Solubility of Carbon Dioxide in Water at Low Pressure, by John J. Carroll, John D. Slupsky, and Alan E. Mather, Department of Chemical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G6, Received March 8, 1991; revised manuscript received June 13, 1991 J. Phys. Chem. Ref. Data, Vol. 20, No. 6, 1991

A model based on Henry’s law was used to correlate the low pressure data (those
up to 1 MPa). The following correlation of the Henry’s constants (expressed on a
mole fraction basis) was developed.


At 20°C, the CO₂ solubility is about 0.7 x 10-5 in mole fraction.  This means that pressurizing CO₂ to one bar allows the water to contain 0.0007% CO₂ by molar fraction.


At 1 bar pressure, the mole fraction solubility is about 0.8.

At first look, these two graphs seem to differ – I’ve got to take a look at them.  Let’s get back to this soon.See tomorrow’s