29 Jan 2015 On applying surfactant theory

A European company asked me to help them formulate a very difficult high-viscosity emulsion. Although my Practical Surfactants site is full of theory, and although I've used a lot of it in other surfactant tasks, my feeling was that these particular emulsions would be too far from the theory and the topic was certainly way out of my comfort zone.

I had to cover all the standard low-viscosity emulsion topics first and there were hints that the key ideas based on HLD-NAC theory were resonant with their specific issues - which was encouraging

I had needed to learn some new (to me) theory in preparation for the meeting and when we got to that point I proudly displayed my new-found knowledge. They politely laughed. What was new to me was well-known in their industry and in their particular case was well-known in the sense of being totally impossible to implement. This was interesting new learning for me and they were generous in not laughing too hard at my ignorance in their own specialist field. Fortunately I had one more idea in this area and it turned out to be new and interesting so my new learning wasn't entirely wasted (well, no learning is wasted - and I've learned from my ignorance of their specific area).

But what was interesting is that the "pure" HLD theory which I had imagined to be just a backdrop to more interesting real world ideas turns out to be game-changing. In their hands it was a precision formulation tool. So then the questions could change to some of the finer details of the theory. It turned out that a few other pure-theory apps (such as the amount of surfactant needed to cover every drop of an emulsions) were of vital importance. We could then start to look more carefully at the specifics of their surfactant systems such as head area and tail size and imagine how to change them rationally to better achieve their formulation targets.

At the end of the session we had a solid set of theory-backed possibilities for formulation refinements. The theory cannot possibly be exact given the realities of commercial formulations - commercial surfactants, for example, are not the same as ideal academic surfacants. But although we cannot predict with confidence the results of the tests, we can predict with confidence that the tests will show trends for good and bad, allowing further refinement.

And this is the key things about HLD theory. If you are lost in surfactant space, most levers you pull will make no difference: you have a bad emulsion, you change something and you still have a bad emulsion. But when you know where you are via HLD, a change in a key parameter will give a measurable effect, for good or bad. Whatever the result at least you know more than you did before you did the experiment. Optimising from such a position is not easy, but at least it's not impossible! Theory on its own is no good. Tests without theory are usually no good. Tests backed up by a good theory, even an over-simple one, are the way to make real progress.

p.s. I had just finished writing this when I got an email from my client. I had proposed some specific changes and they had used my own apps to run the numbers. It turns out that my intuition was wrong and that my proposed benefits would probably be out-weighed by some downsides. This means that they don't have to waste experimental time with the specific surfactants I had suggested. Great. When I teach this stuff, my biggest fear is that I'm not smart enough to get the messages across in a way that will help the client. When I find my apps being used in argument against me I know that it was mission accomplished. When I was in a corporate position and could hire technical consultants, my definition of a good consultant was one who could solve my problems and wasn't needed again. Hopefully that's what's happened with this client.