I found out that Lefranc & Bourgeois are the oldest artists’ high quality colour men in France. They share the same parent company as Winsor & Newton which is why the inside of the box lid of my set of pastels, says LeFranc Winsor & Newton. It is probably only interesting to me and a select few but;
the following passage explains it perfectly and for the full article do visit the website via the link:
The Rise of Pastel in the Eighteenth Century; July 5, 2011; Marjorie Shelley, Sherman Fairchild Conservator in Charge, Sherman Fairchild Centre for Works on Paper and Photograph Conservation
What Makes Up a Pastel?
The basic constituents of pastel are a pigment, a filler (a white mineral which serves to give opacity and body), and a binder (a weak adhesive) that loosely holds the two powdery substances together so that they may be formed into a crayon for use. In the eighteenth century, the ideal crayon was to be sufficiently firm so it could be grasped between the fingers without breaking, yet powdery and soft enough to crumble when stroked across a support. A relatively small range of pigments (mostly the same as those used for oil painting) was used in forming an innumerable array of colors, a feature of the medium still characteristic of today’s pastel box. These pigments were combined to produce the desired hue, with proportional amounts of filler added to produce the tints. This multitude of hues allowed pastelists to work in gradations of tone rather than in color mixtures so as to produce the greatest brilliance.
The process of fabricating pastels in the eighteenth century was complex. Many steps had to be carried out by hand and were varied according to the composition of the color, starting with the preparation of the pigment by grinding and washing. Because pigments have distinctive properties (such as cohesiveness, softness, brittleness), each had to be coordinated with a particular filler (selected from a range of materials, such as chalk, tobacco pipe clay, gypsum, and alabaster) and a suitable binder (among them, gum tragacanth, oatmeal whey, or skim milk) to produce crayons of satisfactory texture. After the ingredients were mixed together the paste was divided and rolled into crayons, cut to length, and carefully dried by air or with heat to avoid imperfections and cracks.
So, looking at the above processes and ingredients it is little wonder then, that these pastels remain the best I have ever used. They are silky to use - artists and drawers among you will know what I mean, they glide effortlessly across the paper, they blend beautifully with minimal effort and they are still mainly in one piece, only cracking when enthusiastic pressure is applied. There is no surface scratching like hard pastels can create, the subtle nature of hue variation is really very pleasing to the eye and there are probably another 100 or so years left in them given my infrequent usage.
So I am now considering either a) using them sporadically again or b) drawing them in situ or c) if I ever get round to doing either, maybe both!