Glycerine Basics and FAQ

Basics

Glycerine, also known as glycerin and glycerol, (see Wikipedia article: http://en.wikipedia.org/wiki/Glycerol) is a liquid widely reputed to be a critical bubble juice ingredient. While it can be useful in some cases, it is not nearly as useful as people generally believe. Even within the bubbling community, its value is often overstated.

That is not to say that it isn't sometimes useful, but its influence on MOST recipes is much smaller than people imagine. In the majority of glycerine-containing recipes that we have found, blind tests have indicated that removing the glycerine does not have a noticeable effect though there are (see below) cases where the glycerine is critical.

People often have the impression that glycerine will turn detergent and water into a professional-quality and friendly bubble juice with which it is easy to blow bubbles. That is generally not the case. A polymer is usually needed to turn water and detergent into a bubble-friendly mix.

Another common misconception is that a small amount of glycerine will make bubbles strong and long-lasting. Small amounts of glycerine have little to no impact on bubble longevity or strength. Substantial amounts may influence the longevity of smallish bubbles (particularly indoors).

These claims might have been true in the early 1970s when dishwashing liquid-based recipes were first circulated but even that is not certain. At that time, detergent formulations were different than they are now in 2013. With some exceptions discussed below, adding glycerine to a mix will not profoundly improve it.

Glycerine has many interesting chemical properties, but those properties generally do not come into play with most recipes that you find. Even when glycerine can have a beneficial impact, it generally requires much more than most recipes call for. Those benefits are often more effectively achieved by other means, such as refining the dilution or adjusting the pH (with baking powder or baking soda+citric acid or other means).

While many bubble juice recipes found on the internet call for detergent, water and glycerine as the sole ingredients, anyone advocating those recipes either does not want people to know the secret of high-quality bubble juice OR has not tried making bubble juice using detergent, water, and an appropriate polymer.

Bubble-friendliness. Bubble-friendliness is what we call a juice's potential for easy-to-blow bubbles. With bubble-friendly bubble juice, it is easy to blow many bubbles with a dip of a small plastic wand. This tendency is strongly correlated with the ease that bubbles can be closed with tri-string wands. With the exception of solutions that have little or no water, glycerine tends to have no impact on bubble-friendliness. Getting just a bubble or two from a dip is a challenge with such recipes, whereas getting many bubbles per dip is easy with water, detergent, and the right amount of an appropriate polymer.

Longevity. Glycerine may, when used in sufficiently large quantities, increase the longevity of small bubbles (such as those blown from dimestore bubble wands and used for bubble sculpture) indoors. This effect requires a significant amount of glycerine (on the order of 10%-30% of the solution by weight). The exact amount will depend on a number of factors. The effect is generally not noticeable with larger bubbles especially outdoors. Even very large amounts of glycerine do not protect medium-sized bubbles and larger against dehydration outside in low humidity. Adjusting dilution and the pH have much bigger impacts than adding glycerine. One bubble sculptor explained it this way, "I use a fair amount of glycerine in my mix for bubble sculpture. It may not extend the lifetime very much, but for me a few seconds is the difference between completing a complex sculpture and failure. Getting a few seconds is important to me in that situation. But I stopped using it for big bubbles." The greatest benefit seems to be to what we would call static bubbles, bubbles that don't move around much, such as those created with the Longevity Test. Even then a considerable amount of glycerine needs to be used for the difference to be significant.

Bubble-friendly glycerine mixes. While glycerine does not noticeably improve bubble-friendliness in typical detergent/water mixes, it can be a critical ingredient in some recipes that have little or no water. These mixes are generally used for blowing small or even tiny bubbles. You can get streams of easy-to-blow bubbles with a dip of a small plastic wand with these mixes. However, if you water the solutions down, they quickly lose their bubble-friendliness. Two example are:

Recipes#A_Simple_Recipe_That_Creates_a_Lot_of_Bubbles_with_Small_Wands
this Dawn Direct Foam-based recipe that I blogged that is great for micro-wands, too.

Quick-take

For giant bubbles. Our conclusion (based on fairly extensive experimentation ourselves and reports of tests by others) is that adding glycerine is unlikely to benefit bubble juice intended for large bubbles especially if those bubbles are created outdoors. Adding glycerine to water and detergent does not improve "friendliness" (the ease with which closed bubbles can be made). For small bubbles (especially blown indoors) glycerine may benefit a polymer-containing juice but only when quite a bit is used. It is definitely useful for mixing up polymer powders that would clump if added directly to water (see Slurry Mixing section of the Polymers article).

For indoor small bubbles. Glycerine can be a key ingredient for making a bubble-friendly solution when combined with some detergents and very little (or no) water. (See Bubble-friendly glycerine mixes above). A glycerine-heavy mix is useful for certain tricks like Rick Findley's String of Pearls.

Bubble domes and static bubbles. Glycerine can extend the lifetime of static bubbles -- such as bubble domes on a light table or static bubbles held on a wand or stand. For such bubbles, the solution should be on the order of 20%-30% glycerine.

Longevity and strength. Glycerine can significantly improve the longevity of small indoor bubbles (such as those used for bubble sculpture) and bubble domes (half-domes) but only when a significant amount is used. For a significant benefit, something on the order of 20%-30% glycerine (by total volume of the bubble juice) is required. For increasing longevity and strength of giant bubbles, adjustments to the dilution (detergent concentration), pH and polymer amount will generally have a much more profound effect than adding glycerine.

'Polymer mixing'. Glycerine is useful as a slurry liquid for mixing polymers even if it doesn't improve the bubble juice itself.

No harm. While we have found that glycerine has an undeserved reputation as a beneficial bubble juice ingredient, it doesn't do any harm. Quite a bit of glycerine can be used without having a negative impact on the bubble juice whereas propylene glycol, another popular humectant, has a narrower range of usefulness.

If you have a recipe or experience that contradicts these findings, please let us know. We want the wiki to reflect truth rather than folklore.

HAVE SOMETHING TO ADD? Let us know!

FAQs

What is it useful for in bubble juice?

Glycerine is very useful for mixing up many of the polymer powders that clump when added directly to water. These polymers are often insoluble in glycerine. They can be mixed with glycerine to make what is called a slurry. The slurry can then be mixed with water and the polymer distributed without clumping.

If it makes up a large enough portion of bubble juice, it may increase the lifespan of small and medium-sized bubbles. However, this benefit seems limited to indoors. For large bubbles, it seems not to be effective.

If you are making bubble sculptures (especially indoors), you may find that glycerine (when used in a large enough amount) improves the longevity of the bubbles enough to be worthwhile. It takes quite a bit more glycerine to have an impact than is found in most common recipes. At less than 10% of the total solution, it might have no noticeable impact at all -- and much more is often needed to have a measurable impact.

Glycerine can be useful for mixes intended for small bubbles. A mix with glycerine and detergent and very little water can produced many bubbles per dip when used with small wands and straws.

In some circumstances, glycerine is useful for stabilizing polymers and as a preservative. However, where bubble juice is concerned, these circumstances seem to rarely be relevant. The preservative action, for instance, is only relevant when there is little free water in a solution. In some applications, glycerine is considered a sort of 'bridge' that due to its unique characteristics may allow some otherwise incompatible chemicals to live "harmoniously". However, this is not generally an issue with the most commonly used bubble juice ingredients.

Are there any drawbacks to glycerine?

Glycerine-containing juice has been reported to harm lawns -- even juice with fairly small amounts of glycerine.

It can be an expensive ingredient when used in large quantities by the homebrewer.

On the plus side, unlike propylene glycol (which is also used for its hygroscopic properties), glycerine won't hurt your bubble juice even in fairly large amounts. I have made mixes that were 50% glycerine. Such mixes can be good for small bubbles but are not practical for giant bubbles.

Does glycerine make bubbles more colorful?

It does not make bubbles more colorful, but, when enough glycerine is used (which is quite a bit), it can extend the lifetime of small and static bubbles significantly. The improved lifetime results in enhanced color stability since it delays the loss of color that accompanies the inevitable thininning of the bubble walls (due to evaporation and gravity). It should be noted that similar color stability can be replicated by adjusting the dilution. Generally-speaking, dilute solutions show improved color stability and longevity compared to less-dilute solutions.

Adjusting bubble colors (what we callColor Profiles) is done by adjusting the surfactant concentration. See Dilution and also Color and Film Thickness.

Is glycerine an effective ingredient for increasing viscosity?

100% glycerine's viscosity is very temperature dependent. At "room temperature" (let's say 65F-70F or 18C-20C), it is pretty viscous. It is even more viscous at cold temperatures. At warm temperatures, it quickly loses its viscosity. 100% glycerine is more than 2.5 times as viscous at 10C as at 20C. At 30C, it is less than half as viscous as at 20C. (See: http://blogs.lt.vt.edu/dpholmes/2013/02/21/glycerolwater-solution-viscosities-table-3/)

At the concentrations typically used in bubble juice recipes, the influence of the glycerine is quite small. If one is simply trying to change the viscosity, the common polymers used in bubble recipes are both more effective and more stable. Quite a lot of glycerine (much more than the vast majority of recipes include) needs to be used to significantly impact the bubble juice viscosity and that impact is temperature dependent since the impact is greatly reduced at warm temperatures.

It bears mentioning that simply increasing the viscosity of bubble juice does not improve its performance. Thicker (as in viscosity) bubble juice does not mean thicker bubble walls as discussed in the Thick Solutions article.

Will it help my bubble juice?

It depends upon what help your juice needs. Generally-speaking, adjusting your detergent, dilution, polymer, and/or polymer amount will be much more effective than using glycerine although in certain cases glycerine can help (mostly for indoor small bubbles/bubble sculptures).

If you are doing bubble sculpture (particularly indoors), you may find it useful for increasing bubble longevity if used in a large enough quantity. You will also probably find it worthwhile to experiment with the dilution. Higher dilutions (lower detergent concentrations) generally have longevity increases due to the thicker bubble walls.

If you are using a poor-quality detergent, it is possible that nothing will help except for finding a better detergent. We sometimes find that people asking about glycerine are using second-rate detergents/surfactants.

If asking whether your juice needs help that glycerine could provide, please let us know:

Size of bubbles you are trying to create
What is the temperature and humidity where you are having problems
Are you working indoors or outdoors
What is your recipe (be specific)
What equipment (be specific) are you using to create bubbles.

MARCH 2015 NOTE: In an outdoor test, in full sunlight with 80F and 40% humidity, Edward performed tests with two 20:1 Dawn Pro Solutions. One solution used glycerine for 30% of its non-detergent liquid (by weight) and the other used water for all of the non-detergent liquid. Both solutions pH-adjusted to 7.6. There was a considerable difference in bubble lifetime for bubbles about 2 feet in diameter or smaller. However, in the somewhat breezy conditions there was no appreciable difference in bubble lifetime for bubbles larger than about 2 or 3 feet in diameter. In these conditions, the 2 foot diameter bubbles were not "wobbly" whereas 3 foot bubbles quite wobbly. The difference in wobbliness is due to larger bubbles having a smaller pressure differential between interior and exterior air pressure.

Should I use it?

It is very helpful for mixing polymers but not so helpful for improving bubble juice. If a recipe calls for it, by all means follow the recipe, BUT, we would recommend also mixing up a batch of the recipe and comparing the two versions in the same session on a few occasions to see if there is a difference in performance.

What do people think it does (for bubble juice)?

Glycerine is hygroscopic. For this reason, people assume that it will help a bubble hold on to its water. This is the case when there is enough glycerine, but this will only benefit the bubble when evaporation is the main cause of the bubble breaking.

It is useful for mixing many polymers because many polymer powders do not dissolve or clump when added to glycerine. In these cases, the powder can be dispersed into the glycerine and then mixed with water to avoid the clumping that occurs when the powders are mixed directly with water.

Glycerine can help some polymers remain in solution although that is rarely a factor with the most common bubble-making polymers, and we have not found it to significantly alter the stability of any of the recipes found on the wiki.

Why is it so frequently recommended?

Good question. It is a question for which I do not have a definitive answer. One part of the answer is that detergent, water and glycerine has been around as a recipe since before better recipes were known. This recipe was around even when I was in middle school (in the early 1970s) when the original Dawn was around. I have no idea if glycerine helped a mix of water and that long long gone original version of Dawn (it might have), but the recipe was around then. As a result, a lot of people knew about that recipe and so it achieved a certain folkloric precedence which has proven hard to overcome.

It has not helped that some professional bubble artists have posted this suggestion on their web sites because they understandably don't want to share their trade secrets. (It should be mentioned that few of them are using mixes radically different from the ones you find documented here on the wiki with the exception of those that are using commercial mixes.

The original notion that glycerine is a magic ingredient may well be related to recipes shared earlier in the 20th century by people using soaps and custom surfactant mixes. Much of the early 20th century research about soap films was done with single surfactant solutions whose surfactants were concocted by the researchers who found glycerine usefulf for those surfactants. The detergents that we use these days are quite a bit different and do not benefit from glycerine in the same way.

Tom Noddy posted this interesting message to SBF, the Soap Bubble Fanciers Yahoo Group (RIP) on the topic of glycerine.

The idea that glycerin is a magic ingredient for bubbles pre-dates the era of Dawn as a central ingredient.

To my knowledge, the superior qualities of Dawn over the other available
detergents was popularized when the Exploratorium's Ned Kahn and I separately
tested many many products in an effort to replicate the big bubbles of Eiffel
Plasterer for use in the new bubble exhibits that were being designed in 1983
for the first ever Bubble Festival at that San Francisco science museum. (All of
those Kid-In-A-Bubble exhibits and the large bubble wall exhibits at science
centers and children museums all date from those efforts we made then to add to
the hands-on aspect of the upcoming Bubble Festival that I talked them into at
that time).

To my knowledge, no one was particularly interested in turning Dawn into a
useful mix for small bubbles back then ... Wonder Bubbles/Mr. Bubbles was
already good and very cheap and available. It was this pursuit of big bubbles
that led to the recognition that Dawn is the good stuff.

CV Boys used glycerin and it is often referred to in the recipes offered by
scientists in their experiments with soap bubbles. I agree with you, Edward,
that its usefulness in the modern recipes is limited and I certainly agree that
it is the one thing that most people "know" about good bubble solutions. I tried
it, even in the early Dawn days, and didn't bother with it for long. It could be
that it was a much more useful product in overcoming disadvantages of soap,
rather than detergent.

Tom Noddy
www.bubblemagic.com