It seems that a number of bubble juice brewers on the forum have attempted to mix guar juice using one or more of the recipes posted and have run into sludge issues. It is possible that this is due to failure to follow the steps as listed for the given recipe, but I've witnessed a case first-hand where steps were followed exactly only to have sludge form hours after brewing. I believe that the variation in results may be due in part to variations in water hardness between the locales of those brewers. In the upcoming weeks, I'll be doing some testing to verify whether my hypothesis that hard water (specifically due to calcium hardness) causes guar juice to develop sludge is verifiable, and if so, at what concentration calcium becomes a problem for guar based juices. If findings indicate that the calcium in hard water seems to play a role in the formation of sludge, I'll attempt to determine how large a role it plays, and outline and test methods for getting around the issue of calcium-hard water in bubble-specific applications. If findings indicate otherwise, I hope to narrow down whether other water properties such as alkalinity or pH have significant effects on sludge generation.

Below you'll find an outline of the experiments I plan to complete. (If you haven't guessed it by now, I'm a nerd, and I'm starting to become bubble obsessed!)


It is known that calcium cations in solution can cross-link with guar gum, causing the guar gum to gel rather than remain a stable component within the solution.[1] I believe that the calcium present in hard water can cause what appears to be well-hydrated guar gum in bubble juices using guar as their primary polymer to gel, thus reducing or nullifying the effectiveness of the guar on bubble performance.

Proposed Tests / Steps

I will use two control substances, tap water and distilled water, as well as dilutions of tap water made using distilled water to verify the effects of calcium-hardness (and other water properties) on sludge generation and the performance of bubble juices using guar gum as their primary polymer.

1. Verification of water hardness, pH, and alkalinity in both water sources

Here I will use commonly available water testing strips to glean a 'snapshot' of the properties of both my tap water and distilled water. This should verify whether the rest of the tests should continue, clearly outline the spectrum of water property values that we'll have control over during the testing, and point out possible factors other than calcium-hardness in sludge generation.

2. Measurement of Calcium-Hardness in both water sources

Here I will use titration testing (using a Taylor Calcium Hardness Test Kit) to measure the calcium hardness of both my tap water and distilled water. This test will give a much more accurate reading of the gradient of possible values for calcium-hardness available within the scope water samples available.

3. Control Sample Generation and Measurement

Here I will prepare two control samples, varying only the type of water used for each sample of bubble juice. This will be a true test of the broader question "Do varied water properties lead to significant differences in guar based bubble solutions." If both controls end up generating equal volumes of sludge, we can assume that the water properties in question do not play a significant role in sludge generation, or that the conditions within which these properties do play a significant role are outside the scope of the proposed experiments.

4. Primary Test Sample Generation and Measurement

Here I will prepare samples of bubble juice using various dilutions of tap water, diluting the tap water with distilled water. I will prepare slightly more diluted water than required for the recipe, collecting this additional volume for sampling using the titration and 'strip' tests described above on the reserved portion. This way, we can correlate the overall dilution percentage (50%) and the apparent difference in water property value. The test-strip method will not provide granular data, but will be useful in understanding the overall relationship between various properties at given dilutions. The titration method will provide granular data in relation to the amount of calcium in each dilution, which is the primary variation being studied in these experiments.

5. Additional Test Sample Generation.

Here I will prepare samples of bubble juice using tap water only, but varying additional ingredient amounts or water properties and making ingredient substitutions where possible. I'd be interested to assess the results of:

  1. Using glycerine or isopropyl alcohol as a slurry liquid - is there any notable difference?
  2. Varying pH of water sample before adding guar - does pH effect sludge formation?
    1. If so, does adjusting the pH before or after the addition of guar effect sludge formation?
  3. Adding salt to an otherwise saltless recipe - does the salt have any affect on calcium-hardness or other water properties?

6. Observation and Measurement of Samples at Set Intervals

Data will be collected in the form of physical measurement (height / volume of sludge layer in a container with a known volume) and photographic evidence at set intervals after the preparation of each sample. Intervals will be calculated on a per-sample basis, so that data represents consistant points in each samples life-span. Adequate spacing will be given between start points in each solution to allow for this method of data collection.

7. Performance Comparisons of Test and Control samples

At a set point after the duration of data collection has been completed, I will attempt to ascertain the performance of each bubble juice. Note that this will be mostly based on opinion, but anecdotal evidence may be useful when others look over these findings. I will try to be as objective as possible when making distinctions between samples. I will ensure that data regarding the relative humidity, temperature, etc. area also taken before testing the samples, and that consistant steps are taken when testing each sample.

8. Determination and Evaluation of Softening Methods for use in bubble-specific applications.

If it is found that calcium-hardness is implicated directly in sludge formation, I will design and perform additional tests to determine how a bubble juice brewer might combat calcium-hardness in their tap water while maintaining overall performance of the prepared bubble juice.

Test Procedures

Preparation of Equipment

I will first machine wash all equipment that might come in contact with ingredients or samples in the experiments. After machine washing, I will rinse the equipment with distilled water to ensure that as much remaining contamination is removed from the equipment as possible.

Consistency in all things

  • I will use a single bubble juice recipe for all prepared samples, varying only the type or combination of types of water used.
  • I will measure all ingredients by weight where possible.
  • I will use identically sized/shaped vessels for the samples, to allow for accurate measurement of generated sludge volume.
  • Measurements will be taken across all samples using standardized procedures.
  • Measurements will be taken at set intervals during the experiment and results for each 

Observation / Documentation 

I will take care to document as much as possible in both written and photographic forms.


  1. Calcium-hardness will be found to be the primary factor in sludge formation outside of procedural error during preparation.
  2. Sludge volume will be directly correlated with the calcium-hardness of the water used in each sample.
  3. There will be a cut-off point or goldilocks zone on the calcium-hardness gradient at or within which sludge is no longer produced in significant volumes.


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