In late summer/early Fall 2014, I was making an effort to catalog the color profile of Dawn Pro at various dilutions and with various polymers. In order to get the most meaningful profiles, sessions were only done early in the morning (after sun up) on heavily overcast days (because the indirect light gives the clearest colors). In Central California, where I live, such conditions are sporadic. As I reviewed the photos, I began to recognize that there are a number of potentially confounding issues: temperature (does the temperature influence the film thickness), flow rate, and wick characteristics. Sessions were done to explore the influence of pH on the film thickness, and I settled on pH range of 7.4-7.6 (except for those sessions done at other pHs for the sake of comparison).
Profiing sessions all used a 48" webfoot microfiber topstring and a two strand (white strands) rayon finish mop yarn bottom string. The color profile of the dilutions were remarkably consistent. Work intervened, and I have only recently gotten back to fill in some of the gaps.
In the last few weeks, I have gotten out for 10 to 30 minutes a few times when the early morning humidity was high and the air pretty still to try out some large loops (100" top-strings) with various top/bottom combinations. I have been surprised at how closely some sessions with 25:1 solutions were yielding colors that were more like what I associate with 20:1. Yesterday and this morning, I made some bubbles at 20:1 and noticed that with these giant loops (with lightweight bottoms) that a small change in growth rate could yield a wider range of profiles than I expected.