You will be forgiven if you look at the above photo and think "hmmmm grey horse poo" - mainly because in days past horse poo would have been an ingredient. What you are looking at is a mix of chaux, sable et chanvre.
We wrote a couple of weeks ago about replacing the bathroom window, and having to enlarge the hole it was going into because of a misunderstanding on my part about window sizes. We managed to get the new window mounted in the hole the same day, but there were one or two holes in the stonework around the window where the tuffeau had broken.
Yesterday Stephane decided we would fill the holes in the almost traditional manner, using chaux (hydrolized lime mortar). The break with tradition comes with the material used to provide insulation and reinforcing: traditionally this would have been a mixture of animal hair (goat or horse) and not to put too fine a point on it, poo. Usually horse poo, because horses have really inefficient digestive systems and the grass (or hay) gets processed without the fibres being broken down. Instead we used the modern and very trendy equivalent chanvre - hemp.