Seconding the polymerics, Pemulen has worked pretty well for me in the past. You can also try low-acyl gellan gum if you want something natural, but you’ll want to control the level of salt carefully and you may want to add an additional liquid emulsifier
Pemulens and Sepigels will NOT spray, only stream out of the closure. Most polymers behave the same. You won’t get much “sprayable” there. I use polyglyceryl esters of fatty acid (PEFA) emulsifiers for sprayable milks, e.g. polyglcyeryl-6 laurate, polycglyceryl-4 stearate or polyglyceryl-10 caprate, etc. Choose your poison but stay away from the multi-esters (any di, tri, penta, etc.) and buddy it up with glyceryl stearate or oleate or another monoester.
Polyglyceryl esters can also be paired with sucrose esters. I like the skin feel and handling of both but the combo even more (that’s just my personal preference, no ‘real’ reason behind it).
True about the rheology stabilisers: I haven’t managed to make any low viscosity product even close to stable without them. However, I also haven’t been able to find one which matches my expectations and self-inflicted requirements ;( . The closest I found are acrylates/C10-30 alkyl acrylate crosspolymers… However, the one I’ve got is Carbopol Ultrez 21, not the best choice for sprayable lotions (but, theoretically, better suited for a high non-water part in the aqueous phase). Maybe Pemulen TR-2 would be better??? Apart from that, I work with high inclusion rates of electrolytes and that’s a really bad precondition for polyacrylates. I’ve also tried a xanthan-guar gum combo (cause more ‘natural’ and better electrolyte tolerant) but the consistency is slimy whilst the cold process glyceryl esters I’m currently playing with don’t result in satisfactory lamellar structures. Therefore, stability is still far from useful even with both strategies together (and it certainly wouldn’t spray… which, in my case, it doesn’t has to). I’m still looking for my perfect rheology modifier.
@Pharma, have you tried the modified cellulose rheologicals? Most are a bear to hydrate, I’ve had to beat on them with a Cowles at 600rpm @ 65C for four hours to get there. However, the ones mixed with cellulose gum hydrate easier and work well. Electrolyte tolerant too! And then there’s that renewable/sustainable thingy.
@chemicalmatt Nope, I have not. I have HEC 5000 (Natrosol 250 M), Lotioncrafter’s HPC (which they don’t seem to offer any longer… so I have no specs ;( ) and MC (wallpaper paste LoL) sitting around on my shelves. I might give HPC a try, thanks for the tip!
The reason I haven’t tried HEC/HPC yet are, under others, the fact that they are ethoxylated/propoxylated, pharmaceutical CMC and HEC gels feel just awful and, maybe most importantly, I’ve totally forgot that I have them. But yes, they’re closer than polyacrylates to what I’m looking for.
However, I would guess that cetyl HEC might be suited best… any advice would be highly appreciated!