Thanks Bushveld, very interesting old movie. The titles are pretty self evident but here is a translation of the slides if it will help:
1. We have filmed the old process of case coloring in the only workshop in the Liege region where it was still used
2. The cement used in this process is composed in order principally of calcinated bones and of charcoal.
3. The calcination of bone begins in the old oven. The fire is lit with gas. At the appropriate moment the flaming bones are thrown into a tank where the calcination is completed.
4. The temperer puts out the fire while covering the kettle with a lid.
5. The calcified bones are ground in a hand mill.
6. The morter that was once was served for this purpose
7. The bones, before and after this treatment
8. The soaking tubs have different dimensions.
9. In order to avoid oxydation the trays are covered with several layers of clay.
10. The pieces to be tempered are arranged on a bed of charcoal and animal black
11. At this point the test pieces are put into place.
12. When the tub is full, the temperer coats the edges with a clay paste.
13. The tray is ready: it’s a package
14. The tray is placed in an electric oven, which nowadays replaces the old “hotchet” oven.
15. Removal of a specimen.
16. Discharging
17. The tub full of water
18. During the actual tempering, the temperer dresses in wet bags.
19. The parts removed from the water are placed in the tray while still hot, to ensure rapid drying.
Excellent. You do not have to speak French to understand the artisanal nature of these manufacturing processes illustrated in these clips. These films are really a treasure. America had transitioned many years before to mass-production (called the "American system" in the UK press after 1851 Crystal Palace exposition).