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For a while, it has been on my radar to compare Propylene Glycol to Glycerine as an addtive for extending the lifetime of bubbles. Several people have mentioned that they believe that it is more effective than glycerine. Others have mentioned that it can interfere with the surfactants when the concentration is too high[1]. In an SBF posting, John Pastorello has recommended not exceeding 0.50%[2].

NOTE (added 3/23/2011): Propylene Glycol seems less neutral in its interaction with bubble solution than glycerine. Technically, it is apparently a 20% more effective humectant than glycerine[3] -- however it appears that it might more profoundly change the bubble skin's behavior more than glycerine at levels high enough for it to increase bubble longevity. I wonder if the loud pop that the PG-containing bubbles make indicates that the surface might be stiff. So far, these solutions were only tested indoors on small equipment. Some testing needs to be done with giant bubble equipment.

2011 03 01 Exploration[]

I was doing some longevity tests of an HEC-containing mix that was 11 parts water and 1 part Dawn Pro. I added a few drops at a time to 1/2 tsp of my base solution. The base solution had an weight average longevity of 17.3 seconds. WT AVG is the average of the best 3 of 5 trials. About the Longevity Test

This was a very rough, preliminary test. So, one should not draw too many conclusions. I am jotting down these rough experiments as useful anecdotes that may point the way to possibilities for further testing. The base solution was about 11 parts water/1 part Dawn Pro and about .08% HEC (Dow Cellosize QP100MH).

Solution AV WT AVG MAX Notes
0301 14.4 17.33 20 base solution
0301+PG1 26.4 30.67 38 base + 2 drops added PG (into 1/2 tsp of solution)
0301+PG2 41.6 49 57 with total of 4 drops added PG
0301+PG3 65 76.33 98 with 8 total drops PG; loud pop; color pretty stable
0301+PG4 58.2 64.33 76 with 12 total drops; color stable/swirly
0301B 29.2 36.67 41 0301 [no pg] plus 4 grams 1% HEC;color pretty stable
 


2011 03 07 Test[]

Base solution was 20 parts tap water to 1 part Dawn Pro and bit less than .004% PEO (a bit less than half of what is in Jumbo Juice)

Solution % PG AV LONG % COMP TO BASE NOTE
0305 0.00% 12.4 100% 20:1 water:Dawn Pro solution .0036% PEO (Jumbo Juice is about .01%)
0305 + 0.1ml PG 0.20% 16.6 134% quiet but audible popping
0305+0.2ml PG 0.40% 20.8 168% audible popping
0305+PG2 0.80% 24.6 198% audible popping / color fading on top at 30 a bit
0305+PG3 1.59% 19.4 156% audible popping
0305+PG4 3.13% 55 444% audible popping. Color drain at top somewhere between 40 and 60 seconds
0305+PG5 4.62% 31 250% audible popping. Color pretty stable though fading a bit

The data look a bit funny at the 1.5% level and above. These tests need to be re-done (at each level there were only 5 repetitions). A plot of the improvement looks strange with the longevity lower at 1.6% than at .8% but then dramatically higher at 3%. It is expected that one will see improvements in longevity until some point at which the longevity crashes due to PG's effect on surfactants.

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