Color Profile is the term that we use to describe the range of colors typical for a particular bubble solution.
As discussed in Color and Film Thickness, the colors of a bubble provide specific information about a soap film's thickness. The film thickness is largely determined by the solution's surface tension which is largely determined by the soap concentration. As long as the bubble device has adequate capacity, the soap film will have what we call the default profile as the bubble grows. If the bubble grows faster than the bubble device can supply juice, the the film may become stretched thinner (just as plastic wrap will start to thin if you pull hard on it). We call range of colors that occurs in those conditions the stretched profile.
In the image below, you can see a tube at several stages as it grows. The bubble juice is a guar-based juice made with Dawn Pro and a dilution of 20:1. The first three stages have the default profile. In the latter stages of its growth, you can see a significant thinning of film -- as the wick holds on to the bubble but is not able to supply enough juice (or enough juice fast enough) to allow the bubble to maintain its normal thickness. The stretched profile may appear for other reasons, too. (EDWARD: EXPAND THIS PARAGRAPH WITH MORE ABOUT WHEN THIS CAN HAPPEN)
Dawn Pro at 20:1Edit
The photo sequence below was taken on a very overcast morning with 80% humidity as a bubble tube gows. This was a guar-based bubble juice. The first three images show the normal color profile for this dilution. The fourth and fifth images show a stretched profile near the loop. These are colors associated with a thinner film. See the scale in the article Color and Film Thickness to see how color maps to thickness.
Stretched Profile NotesEdit
One can see a shift from the normal to the "stretched" profile for a number of reasons:
- Thinning as loop becomes exhausted or can no longer satisfy rate of expansion. As the wick becomes exhausted of juice, it may not be able to provide as much juice as the bubble demands. So, the film stretches similarly to the way that a length of saran wrap or plastic cling film would if you held one end and pulled at the other. The bubble's film stretches as it is pulled from the loop.
- Thinning of the film due to evaporation. This is common when it is warm or the humidity is less than ideal. It also happens if making bubbles in direct sun even if the air temperature is cool. There is a lot of energy in sunlight which is why it can be quite warm inside a car that is left in the sun even on a cool day.
- Thinning due to rapid expansion. If the air is moving fast, it may cause the bubble to grow faster than the wick can feed the bubble. After a bubble is closed, when there are swirling winds, there can be low and high pressure pockets that cause closed bubbles to rapidly expand which will cause the bubble to grow and the film to stretch.
- Thinning due to uneven release of water and detergent. Some (perhaps all?) wicks seem to release the water and detergent at slightly different rates. This seems to result in an increasing soap concentration in some cases.