pH plays an important role in the performance of home-brewed bubble juice. What we call "pH Adjusters and Water Conditioners" are ingredients that are used in bubble juice recipes to improve the performance -- generally through pH adjustment. This article provides information about additives that you can use and recommendations about how to use them. See the pH article for information about the importance of pH to bubble juice.
Baking powder, citric acid, baking soda + citric acid, distilled vinegar, cream of tartar and other ingredients are often used for making bubble juice because of the impact they have on pH.
The optimal pH range for a particular bubble juice may depend on both the surfactants and the other ingredients including the detergent. pH doesn't matter for most of the polymers and additives we use, but some of them (such as Japanese PVA-containing laundry starch) are sensitive to them. The exact reasons for this sensitivity is not currently known.
The effectiveness of detergents can be influenced by metallic ions and salts present in tap water and by calcium and some other minerals. In some (generally rare) cases, water conditioners that soften the water may be beneficial.
Baking powder or baking soda+citric acid are the favored tools for adjusting the pH as they do so gently -- making it hard to overdose a mix, and they do not require using a pH meter. Baking powder is more effective than baking soda + citric acid for reasons discussed below. Citric acid and tartaric acid (cream of tartar) are very effective BUT care must be taken because it is easy to overdo it and ruin your bubble juice if you are not careful. A small amount of citric acid goes a long way.
Baking Powder Edit
Baking powder is the easiest to use pH adjuster and is often more effective than using baking soda+citric acid since the pH shift it creates is more stable. It is premixed to have the acidic and basic components in balance and is hard to overdose. It really should be added as the last ingredient when all your bubble juice's water is present. Baking powder has corn starch in it (often specially treated to be even more insoluble than it normally is) that does not dissolve in the water. Do not waste time trying to get it to fully-dissolve. It will not. The precipitate causes no problems. This is a key ingredient in Mike's Gooey Mix and in the recipe provided with The Bubble Thing. Because it acidifies gently, careful measurement is not required. Recommended amount: about 1/2 teaspoon (approximately 2 grams) per liter of water seems to be the right amount for most tap water. Using more will generally be fine. The first use of baking powder as a bubble juice ingredient seems to be in David Stein's bubble juice recipe that is included with Bubble Thing. IMPORTANT NOTE: Not all baking powder is the same. We have found (Dec. 2013) that some brands of baking powder are less fast-acting than others and may need to sit for a considerable amount of time to take full effect. You may want to try a few different types in your mixes. Ideally, you want a baking powder that bubbles immediately when added to water. Weight/Volume Equivalence: 1/2 teaspoon (2.5 ml) of Rumford baking powder packed is about 2 grams. When the pH is lowered with baking powder, the pH of the juice seems to be quite stable. In a summer 2014 trial, a 20:1 water-detergent mix whose pH was lowered from its normal 9.0 to 6.8 with baking powder remained stable for at least 2 months.
Baking soda. Baking Soda + Citric Acid Edit
Some people use baking soda by itself as an additive to bubble juice, but it is much more common (and seemingly more effective) to use baking soda together with citric acid.
Baking Soda+Citric Acid. Baking soda plus citric acid is a popular combination for adjusting pH. It should be noted that because this method is essentially using dissolved CO2 to acidify the mix, the pH is not stable and will change (rise) over time as the excess CO2 comes out of solution. This method is definitely better than no adjustment, but (as of summer 2014), we feel that more stable adjustment is preferable if you are not going to use your juice up within a day or two. The length of time over which the pH changes is highly dependent on temperature. The warmer it is, the quicker that the pH rises. There is no precipitate when it is used. So, some people favor baking soda+citric acid because it creates a nice clear juice. There will be a slight amount of cloudiness when Dawn and other Procter & Gamble dishwashing liquids are acidified. Baking soda+citric acid (plus water) also creates some sodium citrate which has been purported to have beneficial properties though Edward Spiegel performed experiments in Summer 2013 that seem to indicate that the benefit is almost solely the result of the pH adjustment since bubble juice treated with citric acid alone performed the same as juice made with baking soda+citric acid with the amounts adjusted so that the resulting juice had the same pH. Baking soda+citric acid is beneficial even when distilled water is used. This would not be the case if chelation or water softening (sodium citrate's main benefit) were factors. Weight/Volume Equivalence: approx 0.95 grams per packed 1/4 teaspoon. Recommended Amount: .5 to 2 grams per liter of water used with one-quarter to one-half that amount of citric acid. 1 gram baking soda per liter of water seems to work well for most tap water the with the appropriate amount of citric acid.
IMPORTANT NOTE ABOUT BAKING SODA/CITRIC ACID (AUG 2014): In July 2014: we mentioned that reports from various people indicated that the relative amounts of baking soda/citric acid that people need to use seems to vary. Further investigation is showing that the pH of solutions acidified by using baking soda/citric acid (to create carbon dioxide) can vary substantially over time and is also temperature dependent. We are continuing investigations. Not only are the relative amounts important, so are the total amounts. Using pure CO2 to acidify mixes shows that an oversaturated solution will initially have a pH well below the desirable range but eventually stabilizes somewhere in the range of 7.8-8.2 for a 25:1 water:detergent dilution. With 2 grams baking soda and 1 gram citric acid per liter of water, the initial pH of a 25:1 dilution was about 6.8 rising to 8.2 over about 10 days (temperatures 70F-75F). When using 4 grams baking soda and 2 grams citric acid, the initial pH went as low as 6.4 but rose to 8.7 over the same 10 days. Because solutions are initially oversaturated with C02, the pH can be lower than desired -- but correcting the pH while still oversaturated can result in adding far too much baking soda -- up to 8 parts baking soda may be needed after the fact to bring the pH into the desired range--but once the excess CO2 outgasses, the result is an over-alkaline bubble juice. INVESTIGATIONS CONTINUE! For this reason, baking powder may be the preferred method for adjusting the pH in the absence of a pH meter. At least some baking powder's seem to create a more stable pH profile.
NOTE FOR EXPLORATION: Baking soda + cream of tartar (tartaric acid) is a combination that we have not yet explored but which is likely to be beneficial. Our guess is that a 1:1 ratio of baking soda and cream of tarter would be a good place to start.
Citric acid Edit
Citric Acid is the preferred pH adjuster for many bubblers either on its own (which does require some care to not over-acidify your bubble juice) or in conjunction with baking soda. When citric acid is used directly, it yields a stable pH (as long as your juice doesn't become contaminated--which is true of any juice). When used with baking powder, the pH will be unstable as some of the CO2 responsible for the acidification will outgas over time. See "Baking soda. Baking Soda + Citric Acid" (elsewhere on this page).
Citric acid is available in many grocery stores (often sold as sour salt -- although sour salt is sometimes sodium citrate). It is available inexpensively from stores and web site that cater to home beer-brewing. It is sometimes available from bakeries or stores that sell baking ingredients, too. In some countries, it is sold for the purpose of de-scaling coffee machines.
Weight/Volume Equivalence.: approx. 1.1 grams per packed 1/4 teaspoon.
About the recommended amount (given below). These recommendations apply only to Dawn-family and Fairy detergents. Other detergents may have different optimal pH ranges. The precise amount you need will depend on both your water's pH AND alkalinity (alkalinity is different from basicity and is not simply the inverse of pH). The amounts mentioned should be treated as ballpark estimates. Use them as starting points and use more or less based on your own results. They are based on Edward's findings with his tap water, but your tap water will be different.His tap water in Redwood City, California has a pH that tends to be in the range 9.0-9.02. You want to land your juice in the range of 7.2-7.7. I tend to aim for 7.6 so that if the pH falls you won't fall into the danger zone (below 7).
Recommended amount when using 5% citric acid solution. (Updated July 2017) As long as your water is not extremely acidic or extremely alkaline, these amounts should get your juice into the 'sweet spot'. If you are using Dawn Pro or similar (full-strength Fairy, Dawn Ultra 2x, etc): use approximately 0.14 grams (or ml) of 5% citric acid solution per gram of detergent to achieve a pH of about 7.65. If you are using Dawn Ultra 3x, use about 0.18 grams of 5% citric acid solution is needed per gram of Dawn Ultra 3x. To determine how much citric acid solution you need, multiply the number of grams of detergent you are using times the multiplier. You can generally round up to the nearest gram. For example, for 50 grams of Dawn Pro, you need 50 times 0.14 grams of citric acid solution which is 7 grams. For Dawn Ultra 3X, you would need 50 times 0.18 grams of solution which is 9 grams. Using 9 grams of citric acid solution with 50 grams of Dawn Pro brought the pH down to about 7.3. A total of 10 grams is likely to over-acidify the mix. It takes 3.5 ml citric acid solution to achieve a pH of 8.2.
Using citric acid powder If using citric acid directly approximately 0.3 grams (< 1/16th tsp.) citric acid per 1050 grams of 20:1 bubble juice should land your juice in the sweet spot. When using the powder directly, it is essential that the powder be completely dissolved. Since this takes some stirring, you should add the powder to a small amount of the water or juice, stir until completely dissolved and then add that to the rest of the juice. When using the powder, it is best to measure by weight not volume as measuring dry ingredients by volume is unreliable. And a small error can drop your juice's pH so low as to be unusable.
Making a 5% Citric Acid solution. Using a citric acid solution rather than citric acid powder directly has a few advantages: you don't have to worry about undissolved citric acid (which can cause a sudden pH drop when it finally dissolves) and over-acidification is less likely (a little citric acid powder can shift pH dramatically). A pH meter is recommended (since water acidity and alkalinity varies so much from place to place). An inexpensive one is fine. It is not absolutely necessary. To make a citric acid solution, add 5 grams of citric acid for every 95 grams of water. The powder will dissolve easily in room temperature water. Be sure to stir until it is completely dissolved. Shelf-life is very long. Distilled water is preferred but not necessary. Usage: depending on your water, about 4 to 6 ml. of citric acid solution added to 1 liter of bubble juice is probably about what is needed to get you to a pH of about 7.6. Anywhere from 7.2-7.7 seems to be in the optimal range. A little bit higher is better than a little bit lower than this.
Also see Baking Soda above.
Color change: when using citric acid to change the pH, the solution will became slightly milky/cloudy when the pH drops below about 7.8. You can use this change to adjust the juice's pH with a pH meter by adding a little bit of citric acid (preferably in a 5% citric solution as described above) at a time to your mix but be very careful the cloudiness takes a few minutes to develop. Best to start with a little bit too little then add a little at a time until it just starts to cloud. Keep track of how much you added and you should be able to use the same amount in the future.
Cream of Tartar (Tartaric Acid) Edit
This is a weak acid often used in cooking. 1 gram (about 1/4 level packed teaspoon) will lower the pH of 1 liter of 20:1 tap water:Dawn Pro solution from about 9.0-9.2 to about 7.5-7.8. Juice made with cream of tartar compares favorably (based on preliminary tests in August 2014) juice conditioned with either citric acid or baking powder.
Other notes. 1/4 slightly heaping teaspoon of cream of tartar added to 1 liter of a 25:1 tap water:Dawn Pro lowered the pH from 9.1 to 7.4.
Other Water conditioners Edit
Vinegar. Distilled vinegar can be used to lower pH but trials in July/August 2014 seem to indicate that juice made with vinegar does not seem to work as well as juice conditioned with citric acid, cream of tartar (tartaric acid) or baking powder.
Color Change and Stability Edit
The importance of when you add baking powder or baking soda+citric acid Edit
Getting any benefit from baking powder or baking soda+citric acid depends on when you add these ingredients. Most of the benefit is due to the pH shift caused by the carbon dioxide they give off when they react with water. Some of the carbon dioxide dissolves in the water and forms carbonic acid. Because carbon dioxide is not very soluble in water, only a small amount of carbonic acid is created. The result is very gentle acidification (which counteracts the detergent's alkalinity).
If all of the water is not present when the reaction occurs, the primary benefit of the reaction is missed. While the benefit is subtle in some cases, it is also quite distinct especially once one has experience.
If you add these ingredients to a concentrate and then dilute the concentrate, you do not get the pH-adjusting benefit which is their primary benefit. The ingredients must be added when all of the water is present. For this reason, it can be useful to add the baking soda when making the concentrate and then add the citric acid to the water used for the dilution. Baking powder has the advantage of not requiring careful measurement. So, it is often convenient to simply use baking powder after dilution.
Note that if you use baking soda+citric acid for fizz mixing your polymers, you need to add some more once your mix is at full dilution.
This is easy to test with a pH meter.
Experiments in 2013 demonstrated that contrary to popular belief, the pH change induced by the dissolved carbon dioxide is permanent and does not quickly dissipate.
Historical Note and Analysis Edit
While a few people were using these additives prior to 2011, they were not in wide use. They started being widely used by SBF members in Feb. 2011 and many claim that it has significantly improved their solutions (with no notable dissent).
While the exact mechanism is not entirely certain, it seems increasingly certain (per Edward Spiegel's 2013 explorations) that the benefit is due to the pH sensitivity of the detergents used for bubble juice. There may be additional benefits related to chelation though there seems little evidence for this -- since the same benefit is found even with distilled water where chelation would be irrelevant.
Others have suggested that it is due to the influence of sodium citrate on the detergent's viscosity. Investigations of Alan McKay's claims [editor: add citation] about the benefits of baking soda + citric acid as beneficial to bubble solutions have led quite a few people (with no notable dissent) to feel that the combination is of great benefit to giant bubble solutions. The optimal concentrations of each has not been determined and seems likely to be somewhat related to the water that is used. For some people (possibly people with acidic tap water), the baking soda must be added early in the mixing process (before polymers and soap) and citric acid must be added only after the solution is stable and hydrated. Others find that they can add both together with the polymers. 0.8 to 2 grams of baking soda per liter of bubble juice plus about 1/2 that amount of citric acid per liter of bubble juice seems to be a beneficial range for most people that have reported on their use of these additives. Some people use a ratio of 2 to 1 (baking soda to citric acid) while others use 1.3 to 1 (based on the theory that the benefit is solely from the creation of sodium citrate that occurs when baking soda and citric acid are mixed with water). Others seem to find that some additional amount of baking soda is helpful, although that may be particular to the pH of their water. There have not been any detailed experiments documented, yet.