Oh girls, these walnut-sized amounts Kerastase love so much have been on my mind. A lot.
I couldn't stop thinking about walnut-sized blobs of hair product. Would that be just-fallen-off-the-tree walnut now, I wondered? A mature walnut? A walnut sans its hard covering? I JUST DIDN'T KNOW! There've been times I've woken up in the night, pondering this extremely First World Problem.
So, like the proactive miss I am, I decided to do something about it. I contacted the Kerastase press office, to seek confirmation of my query. No doubt they pissed themselves laughing in the office, but they very nicely responded politely and solved my dilemma.
The answer is ...
You should be using a blob of product the size of a shelled walnut. I'm guesstimating that's about two centimeters long and perhaps one and a half high?
Hair everywhere, breathe a sigh of relief.