Soap Bubble Wiki
Soap Bubble Wiki

Every once in a while, another bubblehead will mention that sometimes during the course of a session their mix seems to get a lot more viscous towards the end and stops working until they add more water. I have always been puzzled by this because I haven't experienced it myself but a lot of people have mentioned it.

One possible explanation is ingredients settling out. I have seen casually mixed polymers settle out slightly. But this seems to happen for people that are very careful in their mixes using bubble juice that shows no signs of settling when left for days or weeks in the bottle. So, it is not likely that over the course of a couple of hours that the polymers are settling out.

Evaporation has been suggested but that also seems unlikely as they are talking about fairly large scale changes in viscosity and evaporation works slowly enough that it is unlikely that enough water has evaporated to have such a large scale impact.

Digression...possibly....

I have always wondered -- and never been given a decent answer -- why, with some bubble juice (especially juice that is not very, by my standards, dilute) and a high-capacity loop, when you make a lot of bubbles from a single dip, you have bubbles at the end that are nearly colorless.

For some reason, these two issues have been on my mind lately, and it dawned on me that our bubble wicks (the materials that we use for our loops) might not have equal affinities for all the ingredients in our bubble juice. Our wick might be taking on slightly more of some ingredients than others just as in paper chromatography . The difference in affinity is small enough that it only shows up in special cases -- such as when a lot of bubbles have been made from the same dip -- leaving the solution just different enough at the end than it was at the beginning to make a difference. And maybe, if we have a large bucket full of juice and make a lot of dips of our wicks, we are removing slightly unequal amounts of our ingredients.

This might explain why it is only noticed some of the time. The difference in affinity is small enough that in most cases it is negligible. But with a large bucket and a large number of dips, the difference in affinity might be just enough to shift the dilution.

My speculation is that some wicks have slightly more affinity for the water than the rest of the ingredients. Keep in mind that many of our polymers don't really dissolve. Many (most? all?) form suspensions. Perhaps, the wick sometimes absorbs some water from the suspension and leaves a few polymer moleculels behind -- just enough so that after an hour two of bubbling the juice has less water than it should.

From the observed phenomena, it seems like wicks (at least some of them) might have a slightly stronger affinity for water than the other ingredients -- so they remove ever-so-slightly more of the water than the other stuff -- and it might hang on to that water every-so-slightly more over the course of the dip.

I wonder, too, whether there is a distinction in solution that adsorbs to the wick (sticks to the surface of the material) and the juice absorbed by the wick.

Comments?