When I came up with the HEC-based recipe (16 parts water, 1 part Dawn Pro, 8 grams Cellosize QP100MH HEC per gallon of water, 3.2 grams baking soda per gallon of water and 1.6 grams citric acid per gallon of water), I wasn't sure if the baking soda/citric acid were important. I threw them in because I had been intrigued by some posts on SBF about them. (NOTE: Tonight's batch had more baking soda/citric acid than usual: 1.5 grams baking soda and .8 grams citric acid for 24 oz. tap water)
Tonight, the humidity is pretty low (40%) and the temperature is a nice 65F with no breeze. I mixed up two batches of the HEC-mix last night. One as noted above and another without any baking soda and citric acid. I went outside to try the mix that doesn't have the baking soda/citric acid. I started with a new loop made from t-shirt material that I haven't used yet. This 32-inch top-string loop should be able to easily create 50 foot tubes on a decent day. I was lucky to get a 3-foot tube before the film broke. Thinking that the problem might be the loop since 40% isn't usually this awful, I grabbed a pair of Dip Stix. Same result. I could make 2 foot bubbles but they mostly popped after a few seconds. It was tricky to pull anything longer than 3 or 4 feet: move too fast and the film broke, move too slow and the film broke.
I went inside and grabbed the mix that includes baking soda and citric acid and a fresh set of Dip Stix. Very different. I was easily pulling 10 foot bubbles walking slowly or briskly and the bubbles were lasting about 30 seconds. I then tried those Dip Stix in the other solution -- just in case I had failed to clean the wand after its last use. After a few dips, things were exactly as with the first set of Stix. Pop. Pop. Pop. I then mixed the two containers and both set of Stix worked well. This probably indicates that my current proportions may have more baking soda/citric acid than is needed.
This is just a preliminary test with no video record. So, this can't be treated as definitive. And perhaps it only makes a difference in some circumstances. But tonight, those two mixes behaved very differently.
The viscosity of the two mixes were within the margin of error of each when measured by timing how long it takes to drain from a 20 ml syringe. They were a bit more viscous than Jumbo Juice. (Water takes just about 10 seconds to drain on average and these solutions averaged just over 13 seconds. Jumbo Juice takes about 12 seconds).
ADDENDUM: Read this related follow-up.