20121028 B composite triptych

Giant bubble created with a modular loop: 100" full-ply mop string top and 220" single strand bottom (single strand of deconstructed rayon mop yarn)


Most people are using tri-string loops that use the same wick material for the top and bottom strings (or top and side strings). This design is convenient but not necessarily the optimal way of doing things especially for large loops. For a number of reasons, it is often beneficial to use different materials for different parts of the loop. Apparently, quite a few people have come to this same conclusion independently, but this topic is rarely discussed. It is often beneficial to use a high-capacity top string with a much lower capacity bottom string.

[THIS ARTICLE IS IN PROGRESS AND NEEDS REFINING -- but I believe that even in its current state that it provides valuable information for people using tri-string loops -- especially large ones.]


My speculation about composite loops started in 2010 shortly after I became interested in giant bubbles, but I didn't pursue it as I was focused on experimenting with bubble juice ingredients. My interest was piqued as the result of a few things that happened in proximity:

  • my first exploration of really large loops included a 10-foot top-string loop made of a single strand of cotton cooking twine. It was able to create some really nice bubbles and was easy to manage. Thommy pointed out that it was evident from the color of the tops of the bubbles that the top-string was running out of juice before the bottom/side-strings. This loop couldn't create tubes as large as some other loops I tried, but the difference in size was much smaller than I anticipated, and the loop was much easier to open and close in the non-ideal circumstances in which I usually have to bubble.
  • a discussion that I had with Sterling Johnson about our mutual preference for lightweight loops and also about the issue of whether or not to use a washer or other weight on the loop. Sterling and I share a preference for lightweight loops that have a balance of maneuverability and capacity. These loops hold enough bubble juice to make long tubes and large bubbles but may produce fewer large bubbles per dip in the bucket than some heavier materials. These materials also tend to go through bubble juice a lot more slowly than heavier drippier materials. Sterling mentioned in passing that he had stopped using washers on this loops entirely because he found that it got in the way of the tendency of these loops to start to self-close as the bubble juice drained. Perhaps because most of my loops up that point had washers on them, I hadn't really noticed this 'self-closing' characteristic of some loops. The conversation got my attention. So, I started to explore this phenomenon.
  • an observation that in windy conditions (which is the norm in my neighborhood) it is often hard to close a very large loop (let's say 10-foot top string) before the bubble breaks because of the time lag caused by the loop's inertia. It takes a little while longer for the loop to open and close when you start spreading the handles and bringing them together. The lag isn't huge, but it is quite noticeable with a large heavy loop because of all that inertia. If the conditions aren't just right, you may have to start closing the as soon as you get it near fully opened. The bottom strings continue the outward motion for a little bit even after you have reversed your motion.
  • lastly, the difference in size between bubbles created with really large loops of different materials was much smaller than the difference in capacity of the loops.

Upon reflection, it was quite clear that the maximum size of the bubbles -- even under ideal conditions -- with a standard uniform tri-string (all parts of the wick a uniform thickness of the same material) was more closely related to the capacity of the top-string than of the rest of the loop. The top was often being drained long before the bottom-string. All that extra capacity was being wasted -- and with very large loops that unused capacity in the bottom string was making the bubbles harder to close without contributing a benefit.

It seemed likely to me that there would be a lot of advantages to creating loops (especially large ones) that made use of different materials or different thicknesses of the same material for the top and bottom strings. The choice of particular top and bottom would depend on the particular goal or situation.

Just about the time that I started thinking a lot about this, I got so busy with my real life that I didn't have the time to pursue any exploration of it. I did some asking around to see if any of my pals were exploring this. I was told (but haven't yet confirmed) that Alan McKay has explored this and uses composite designs. When I met Brian Lawrence in person for the first time (in July 2011), the topic came up and he mentioned that he mostly (always?) uses composite loops.

Even though it seemed obvious that composite loops was the way to go, I was daunted by the number of combinations of top and bottom strings that it would be necessary to test to come up with meaningful conclusions. So, I didn't do anything about it for a long time. One day it occurred to me that I didn't need to make a new loop for each possible combination that I wanted to test. I could create tops and bottoms of the materials that I wanted to use and just clip them to my wand leads. Originally, I clipped the top and bottom strings together in order to bind them together. Then I tried the loops without binding them and found no obvious difference in behavior (although I have not really tested sufficiently to say that the binding would serve no purpose). If binding is useful, however, it doesn't require a "keeper" or binding clip -- it would be enough to clip the top string on first followed by the bottom string -- optionally wrapping the bottom around the top one time.

Uniform VS. COMPOSITE Tri-String LoopsEdit

Advantages of uniform loops. Convenience (this can be significant). For small and medium tri-strings, the advantages of composite tri-strings may sometimes be outweighed by the inconvenience of finding the right combination of materials.

For large tri-strings, I think that the advantages of composites are worth the effort.

Advantages of composite loops

  • Composite loops can achieve much more efficient use of bubble juice than a uniform loop with little or no impact on the maximum size. Uniform loops often consume many times more juice than a composite loop whose bottom string has less capacity than the top-string. See the picture below of a monster made with a full-ply rayon mop top-string and a single ply of deconstructed mop yarn for the bottom string. The biggest bubbles that you see on the wiki were created with bottom strings that are lower capacity than the top-strings. Most of Edward's supergiants made since 2011 have been with a full-ply mop yarn top but only a strand or two or twine or deconstructed mop yarn on the bottom. (See: Edward's Big Bubble Rigs
  • Composite loops with the right bottom string can often better "feel" and control than a uniform heavyweight loop.
  • Inertia. Heavy bottom strings have a lot of inertia (by definition). It takes a little longer to get them moving and once they are in motion, the motion continues with more force. As a result of this, it is tricky with heavy bottom strings to have fine control at closing time.

Some people prefer heavy uniform loops. There is no question that some amazing bubbles have been created with them. If you are used to such heavy loops, it can take some time to get used to using a lighter weight bottom string. But over time, this will often translate to improved control. Different bottom strings may be appropriate for different situations and conditions.

Choice of materialsEdit

The choice of materials depends both on personal preference (people seem to have highly personal preferences as to what materials they like) and the goal. Highly self-closing bottom strings have certain functional advantages under certain conditions (such as high wind) that become liabilities in other conditions (calm conditions). I find that a variety of combinations serve different purposes. Very light bottoms can be responsive and fun but can't compete with bottoms that hold more juice. But, as you experiment, you will often find that increasing the capacity of the bottom string does not increase the capacity of the loop.

For example, when using 4-ply rayon mop yarn for the top string of a very large loop (6 to 10 foot top string), a bottom string made from just two-plies of the mop yarn seems to yield the same size and quantity of bubbles as a bottom string made from a full 4-ply length of the mop yarn. Even a single ply bottom string comes quite close in capacity to the full 4-ply bottom. The single or double-ply bottoms use up a lot less juice and are much easier to maneuver. Note that this yarn is so absorbent that the single-ply bottom is only barely self-closing and only as the juice drains. It is self-closing enough to be friendly but not so much as to cause problems. The two-ply bottom is not really self-closing but it is very responsive.

Why use a heavier top than bottom string?Edit

There are quite a few advantages to using composite tri-strings with top-string whose capacity is higher than the bottom-string.

2/3 of the loop's length is contained in the bottom string (or side strings) but much of that material is only serving the lower part of the bubble -- whose excess juice quickly drains to the bottom and drips off. On the other hand, the top string provides juice that ultimately serves the whole bubble. Gravity, the inexorable force that it is, causes bubble juice to drain towards the bottom. Juice that enters at the top of the bubble can replenish parts lower down. But the bottom string (side strings) is providing juice that serves less and less of the bubble the farther down the string that you go. Any excess travels quickly to the bottom.

The bottom string's bubble juice can't be used completely because the top string will be drained long before the bottom of the bottom has been exhausted. Notice these pictures of a large bubble made with a standard uniform loop (a single strand of heavy cooking twine). The pictures were taken less than one second apart as the bubble reached its maximum size and was released. Notice the color of the top which indicates that it is quite a bit thinner than the bottom. This same phenomenon is true with heavier weight loops, too although it requires that you make a larger bubble before it is so evident.

Capacity and Size: A typical 6-foot diameter bubble only needs about 3-4ml of bubble juice!

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Early bubble formation

Half-second later. Notice how thin the top has become. It is dangerously thin because the top string becomes exhausted in advance of the bottom string (or side strings).

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A moment later you can see that the top string can not supply enough juice to the top. It is dangerously thin.

You can see some video taken with composite modular tri-string loops in this blog entry.

Read about modular tri-string loops. They make exploring composite loops much easier since some experimentation may be required to find the right top/bottom combination.

Food for thought. It may well be that the ideal composites may have involve more than two different materials. It is easy to imagine that there could be some advantage to the top of the side strings having more capacity than lower down and for the center of the top-string to have some added capacity.

World record BubbleEdit

Megan Parker's world-record bubble [1]  was created with a composite loop: 9-foot top-string of full-ply RubberMaid Microfiber Webfoot yarn and 19-foot bottom string made from two strands of deconstructed RubberMaid rayon finish mop yarn .

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