In case yall didn't know (I didn't) or were interested, StarSan foam freezes before the liquid does, and I don't mean by a few minutes either. I brewed on Saturday and left the StarSan in my wall paper tray in the garage, by evening when I cleaned it up the foam had frozen into slush (that didn't melt back into liquid in my hands) but the liquid was still fluid. I kept the foam in a jar over night and it is still slush. I put the jar into the ferm fridge to warm (set at 68*F) and see if it will go back to liquid. The StarSan in my gallon jugs has frozen foam as well, but the liquid is still fluid (in the garage as well). The foam in spray bottle froze as well and froze the line and pump in the sprayer making it useless by brewday's end. Here is a pic of the frozen foam in the wall paper tray after draining the liquid back into the gallon jug:
So does that mean StarSan foam and StarSan solution separate into different substances and are not just two different states of StarSan? Edit: or maybe just different concentrations of the non-water ingredients in foam vs liquid? I don't really know how to science.
I think it just means that there is a lot less thermal mass to a foamy bubbles than there is to the less foamy liquid portion.
Great question, hopefully we get some good conversation on here about it. I thought it was interesting, especially that the liquid in the gallon jug is still in liquid state 36 hours later. Outside temps have been below freezing since Friday, hovering between 0-20*F.
Salts dissolved in star san solution lower the freezing temperature of water. I'm guessing that this is at the root of your observation.
I've found the foam freezes pretty quickly. My brew on Friday was a prime example- the foam froze on the surface after just 15 minutes (it was a block) and also froze the lid on the bucket before I got it inside. It was 4F out so that is not shocking.
If one f these fellows could check the respective pH of each state we could find this out fairly quickly. But I suspect pweis909 to be correct, as this is his bag if I'm not mistaken.
Starsan contains dodecylbenzenesulfonic acid as one of its primary ingredients. What you're seeing at low temps (freezing) in the foam is dodecylbenzenesulfonic acid hitting its cloud point (where it phase shifts into two phases) followed by freezing of the foamy, phase shifted clouded layer (due to decreased thermal mass). The frozen foam won't immediately become miscible upon warming because it is too concentrated to go into liquid form; if you dilute it back into water and warm it, it should go back in. Pweis salts influence cloud point temperature as well as the critical micelle concentration (CMC; the concentration where any additional detergent added to the system goes from monomers to aggregates) as well. If you guys want to know more about biophysical properties of detergents, heres a good link (Anatrace has a nice manual as well; I used lots of detergents in protein purification and neuronal preparations): http://www.sigmaaldrich.com/technical-documents/articles/biofiles/detergent-properties.html
Good info here, thanks guys. After a day in the ferm fridge the foam thawed back into liquid. I will do the same with my 2 gallon jugs and spray bottle, then mix them back together and redistribute (so I don't have an unequal solution from the freezing, removing, thawing, re-adding).
