About this article. This article is not a recipe (those are found elsewhere on the wiki). This article is intended to as an introduction to concepts critical for understanding how bubble juice works. If you are an experimentalist, this information is critical and will save you a lot of frustration. If you are just looking for a bubble juice recipe, visit the Recipes page. Come back here to learn the basics when you're ready to start experimenting seriously.
If you are new to bubbling, you may want to check out the Getting Started page.
Soap bubbles and the "juice" used to make them are full of surprises. The physics and chemistry of soap bubbles is quite complex and many important truths are counter-intuitive. There are a lot of myths (aka conventional wisdom) that seem intuitive -- yet are flat-out wrong. We hope this article will lead to a better understanding of bubbles and make your explorations more fruitful. If you find errors or have results that contradict our conclusions, let us know. Our goal is to be fact rather than myth based.
This article outlines the basics of bubble juice as we understand them and is based on countless hours of experimentation here at the wiki and around the world. Over the years, we have revised our view quite a bit as experimental evidence has sometimes demonstrated that widely held beliefs on this subject have often been mistaken -- or based on incomplete information.
Bubble Juice Composition Basics Edit
THE BIG THREE
- Water (required)
- Surfactant (required)
- Polymer/goo (nearly essential)
- ph-Adjuster (advisable)
- Humectants (only sometimes useful)
- Chelating Agents and Water Conditioners (only in special circumstances)
Generally-speaking, effective bubble juice requires three classes of ingredients and often benefits from some additional types of ingredients. The critical ingredients are: water, surfactant and a polymer. It is possible to make bubbles with just water and surfactant, but such solutions are difficult to use. Polymers make bubbles easy to close and often provide additional beneficial properties.
Water and Surfactant. You cannot have soap bubbles without surfactant (soap or detergent) and water. The choice of surfactant is critical. If you are making your own bubble juice, you will usually be using a dishwashing liquid. See the Detergent article for information about recommended detergents. Generally-speaking, you can use whatever water is most readily available. Contrary to popular belief, distilled or other purified water is not preferable to tap water. There are cases where tap water can't be used but those are relatively rare. Read all about water here.
Polymers and goo-makers. It is not easy to make bubbles with a mix that is only surfactant and water. The next most important ingredient class is what I sometimes call "goo-makers". These are usually (always?) polymers. Polymers can be natural products like guar gum (which is a simply a powder made by grinding up a particular kind of dried bean) or synthetic products such as Polyethylene Oxide (PEO).
What is a polymer? A polymer is nothing more than a large molecule made up of chains of similar subunits called monomers.
What do they do? The precise role that polymers play is a mystery. Despite widespread belief, numerous experiments have shown that polymer benefit is not directly related to viscosity. Some polymers are highly effective without changing the viscosity significantly while others are only effective at levels that result in very viscous juice. As far as we know, no one yet understands the polymer role well enough to predict its benefits by looking at polymer characteristics. Trial-and-error is currently used to determine which polymers work well and what properties they bring with them.
Useful polymers add stretchiness or suppleness (which some people -- mistakenly in our opinion -- call elasticity) that allows the film to stretch without breaking. The most useful polymers also provide a property that is often called "self-healing": the ability for a bubble to re-close (heal) when tiny holes appear on the bubble surface. Self-healing and suppleness make it easy to blow bubbles in bubbles. Supple bubbles will deform when attacked by external forces rather than pop.
Much more information can be found in the main Polymers article.
Where is the glycerine? You might be surprised that glycerine is not listed as a primary ingredient. While glycerine is often listed as the critical ingredient in many recipes that you find in print and on the web, much experimentation has shown that its reputation is undeserved. You can make world-class long-lasting bubbles without it. Find out more in Glycerine_Basics_and_FAQ
Other Optional Ingredients Edit
pH Adjusters. These are sometimes referred to as buffers, but buffering is the act of stabilizing pH rather than simply adjusting it. Some of the pH adjusters may also buffer. But the most commonly used ingredients adjust the pH without actually buffering the solution. These are useful because the effectiveness of most surfactants changes with pH. The ideal pH for a bubble juice depends on its ingredients. The most common pH adjusters are baking powder (which is almost impossible to misuse) and the baking soda/citric acid or baking soda/tartaric acid combination. Citric acid and tartaric acid are very effective also, but require a pH meter to make sure that you don't overdo it. Beer and carbonated water are sometimes used as well. Adjusting the pH to the correct level has an impact an many bubble qualities: soap film wall thickness, longevity, "strength", and friendliness. See also: PH
Humectants. These are ingredients such as glycerine and propylene glycol that technically-speaking slow down evaporation due to their affinity with water. However, in practice, humectants often have little or no impact on actual bubble longevity. Most recipes that you find that call for glycerine do not actually use enough glycerine to measurably impact bubbles. There are certain situations in which humectants are helpful. See Glycerine and Glycerine_Basics_and_FAQ
Chelating agents And Water Softeners. In some conditions, water is so mineral-rich that a water conditioner that provides chelation or water softening is needed. Such conditions are quite rare when using commercial dishwashing liquid as your base.
Freeze-preventers. If you are bubbling in freezing and near-freezing temperatures, additives may be useful to prevent freezing. Calcium chloride and propylene glycol are sometimes used to this end. See Cold Weather Bubbling
The dilution (the surfactant concentration) is critical as it largely determines the soap film thickness (which determines strength and color profile and influences longevity) and other important soap film characteristics. The relationship between bubble wall thickness and soap concentration is the opposite of what most people assume. Dilute solutions result in thicker bubble walls than solutions that are more concentrated.
Dilution can have a huge impact on bubble longevity, color, the number of bubbles per dip, and bubble size. In some cases, you need to determine which quality is most important and adjust the dilution accordingly.
See Dilution for more on this critical topic.
Viscosity is a widely misunderstood aspect of bubble juice. Because commercial bubble juice (and many commercial dishwashing liquids) is often very viscous (thick), people often associate viscosity with effectiveness. While polymers change the viscosity of a water/detergent mix, the viscosity change is not the critical factor. Some polymers (such as PEO) can have a profound effect while barely changing the viscosity while others polymers may increase viscosity significantly and only marginally improve the mixture. The precise mechanism by which polymers improve bubble juice is not know. For more on this subject see Viscosity and FAQ:_Thick_Solutions and Polymers.
While some bubbles pop into a fine mist or droplets, some bubble juice create bubbles that seem to break up into tissue-like fragments (it is really just the turning into bits of foam) that we call "ghosts". Ghosting is related to the surfactant being used and is not an indication of a problem. Reach all about them in the Ghosts article.
See Also Edit
The following articles are critical to gaining a deeper understanding of bubbles and bubble juice:
- Site Index - the site index lists many helpful articles that you might otherwise miss!
- DIY Surfactant Base
Distilled water is best. Tap water generally is preferable. With the exception of extremely hard or mineral-rich water, tap water usually performs as well as or better than distilled water in a mix that includes appropriate pH adjustment. See Water
Glycerine is an essential ingredient. Testing has proven this simply isn't true with the dish detergents now available. See Glycerine_Basics_and_FAQ
Thick solutions make strong or thick bubbles. The thickness (viscosity) of a solution has nothing to do with how strong, thick or colorful bubbles are. Because commercial bubble juice and dishwashing liquids are often quite viscous,people often associate viscosity with effectiveness. Some of the best bubble juices have a viscosity closer to water's than to the viscous solutions people often associate with soap bubbles. See Viscosity and FAQ:_Thick_Solutions
This article is an attempt to provide some important basics that can help people explore bubble juice mixology. Most of the information here is discussed in greater detail elsewhere on the wiki. My hope is that this article will provide a quick orientation.
People often tell me that they have tried this or that bubble juice recipe and want to know how to make the bubbles work better. Often, they suggest things that they think that they should try. I asked most of those questions myself when I got started. When I got started, there were lots of recipes to be found and lots of discussion of bubble juice issues on SBF, the Soap Bubble Fanciers Yahoo Group, but there was not much in the way of specific information that could be used to help decide which avenues of exploration would be fruitful.
Don't just take our word for any of this. Explore and experiment. Here is our claim: the information here is based on a lot of experimentation and review of experiments by reliable sources. We have tried to set up experiments to determine the truth and accuracy of what we claim to be true. If you have an experience that contradicts anything you have read here, PLEASE let us know -- we strive to update the information to reflect reality rather than our prejudices.