UPDATED JULY 9, 2012
[NOTE: a little video demonstrating this phenomenon will be added soon.]
I am fond of making bubble juice concentrates for a few reasons:
- they tend to have long shelf lifes since it seems like the micro-organisms that normally feast on the polymers don't thrive in a concentrate's environment,
- they save shelf-space (with eGoo, for instance, a one quart bottle holds enough goo for a few gallons of finished bubble juice),
- they are time-efficient. It takes pretty much the same amount of time to make enough concentrate for gallons of bubble juice as it does to brew one quart of bubble juice.
I started exploring guar-based mixes about the same time that I was finishing up the eGoo recipe. Once it was established that people were enthusiastic about their results with guar gum-based recipes, I started working on trying to create a guar gum version of eGoo. But, so far, it hasn't worked out as there seems to be some sort of incompatibility between these factors:
- concentrated water/detergent solution (how concentrated hasn't been determined)
- guar gum
- baking soda, sodium citrate, or baking powder
When all of the these factors are present, the guar gum will settle out as an increasingly dense disk of gel. Remove any single element and the solution is stable and uniform. For instance, a dilute solution with all these elements works great and has a reasonable shelf-life. I have used it after a few weeks on the shelf and it worked great and did not show significant settling. A concentrated solution that was just water, detergent and guar showed no signs of this gel formation after several days. A solution that also had citric acid (but no baking soda) also showed no signs of the dreaded gel disc.
At first, we thought that maybe the problem was related to minerals in the water or the mixing method. However, even with both mechanical mixing with a lab-quality stirrer and distilled water, the problem persists.
To confuse things, one member our little guar study group reported that a similar concentrate that also had HPMC did not show signs of this gel formation.
We don't want to leave out the baking soda/citric acid or baking powder as they seem to make a big difference. Several people have reported that the mixes perform much better with one of those present in the mix.
I have tried using quite a bit of glycerine as it often works to help polymers stay in solution. But it seems not to be making a difference.
If you dilute the solutions, once the setttling has started, you can get a nice-looking uniform solution but it does not perform well. So, even if you dilute before the disc has formed, you end up with mix that doesn't work well for big bubbles. (Strangely, it worked ok with a garland wand and small rigid wand, but with a tri-string of reasonable size, the film breaks upon opening of the wand). Somehow the guar is changed. Even if you mix up this concentrate and make use of it before the disc has formed, the solution does not work well as a dilute solution freshly made.
Color change. One thing that Thommy noticed right away when we started exploring this is that the color of a guar/water solution changes when you add any of the following: baking soda, baking powder (probably because it contains baking soda), or sodium citrate. The solution changes from a milky white to a yellowish color.
In our experiments, the rate at which the disk formation happened seemed related to the detergent concentration. We did not however explore whether the rate at which it happened changed if the detergent concentration remained constant and the amount of guar varied. Our base test solution was:
- 100 ml water (tap or distilled)
- 0.75 grams guar gum (also tried 1 gram)
- 1 gram baking soda/0.5 grams citric acid OR 1.2 grams sodium citrate
- 40 grams Dawn Pro (or Fairy)
With these proportions, the disc was quite evident within 12 hours and after 36 hours was noticeably denser. It starts as sort of cloudy dense layer and gradually turns into a discete gel disc.
With just 25 grams of detergent, the mix seemed good after 24 hours but the dreaded settling started to be evident after 48 hours. An attempt to use this mix (by diluting with 900 grams water and an additional 15 grams detergent) resulted in a poorly performing mix.
Mix with disc removed. I have removed the gel-disc and diluted the remaining clear solution with the appropriate amount of water and it behaves as if it were just detergent and water.
I have a test solution with 200 ml water (and all the rest of the ingredients the same) sitting on the shelf. After one week, there is some denser stuff but it seems stable. I will let it sit for a week or two more and then compare it with a fresh-mixed solution.
To be continued. We are still investigating. So, hopefully, we will find an answer....
UPDATE JULY 9, 2012: I just diluted a concentrate made on June 21, 2012 that used 200 grams water instead of the 100 grams used for the failed concentrates. This concentrate developed a slightly denser layer that took up maybe 10% of the volume, but the layer was not solidified and discrete the way that the guar disc developed in the concentrates with only 100 grams of water. I will post a picture and video. This layer developed over the first day or two and never became more dense. When the bottle was turned over, it would mix in easily. I used it on July 8, 2012 to create some beautiful bubbles that you can see here.