I haven't had much time for bubbles. Over the last 6 weeks, I have spent a little bit of time following up on some pH issues that people have reported, revisiting some conclusions made when I first looked into pH a few years ago.
I should say that since I realized how forgiving baking powder is (while fine-tuning the guar juice recipe), I have rarely used baking soda/citric acid except during last summer's Charmy explorations the past year or so.
The pH explorations are ongoing and (given some of the erroneous conclusions that I reached earlier) will take a while before they are definitive.
I wanted to check-in briefly for those that can make use of the information.
Baking Soda/Citric Acid. The 2:1 baking soda:citric acid ratio that we have recommended, will result in better juice than unadjusted juice BUT the pH is somewhat unstable. The juice will start out with a pH of just under 7 for all but the most alkaline or acidic water but will rise to the low to mid-8s over a week or so. The final pH is somewhat dependent on the temperature since CO2 solubility varies with temperature. The very initial pH drop can be low enough that the juice might not work well until it has outgassed a little. When using this ratio, the juice will perform best in the first few days after mixing. Tests will be done with 1.5:1, and 1.3:1 and 1.25:1.
Vinegar. A comparison of 20:1 juice whose pH was lowered to 7.4 with vinegar performed much worse in two trials than a juice whose pH was lowered with citric acid. These were PEO-based juices.
Citric Acid. A 5% distilled water/citric acid solution is a convenient way to adjust bubble juice pH with citric acid. About 6-8ml of a solution per 1 liter water will put juice made with most water into a range of 7.6-7.8. This is equivalent 0.3 grams of citric acid. Obviously, using straight citric acid has little margin for error. There does some to be a slight downward pH drift over a few days that stabilizes.
Baking Powder. I have used Clabber Girl (a double-acting baking powder) for my tests. It results in quite stable pHs. Even after several weeks, the pH was in the target zone. I am not sure if this is beause baking powder is less pH-balanced than earlier assumed OR if the heat-activated acid reacts slowly over time to have a buffering effect. I was also surprised to find that a concentrate simulation resulted in a good pH after dilution -- this contradicts earlier tests. Perhaps, the type of baking powder makes a difference in this regard. This needs to be followed up.
MYSTERY. It remains a mystery why Dawn Pro+distilled water has a higher pH (9.0) than pure Dawn Pro. It has been suggested that Dawn Pro does not have enough water for its pH to be meaningful.
..... to be continued ...