Bluthner was the only maker of the 3 that allowed me to take photos. As Christian said, one can take all the photos one wants, you still won’t be able to build a Bluthner, and he’s right.
The factory is a familiar sight of individual craftspeople working on individual pianos, with a mixture of machines for doing various steps, primarily wood working such as planing and trimming.
There are, in my mind, 3 unique structural features of the Bluthner. The first is the sectioned inner and outer rim. Bluthner uses a laminated rim, as is common in piano building. To those new to this, laminated simply means layers of red beech glued together in a mold. This is a very familiar and traditional method of making a piano rim.
However, instead of being bent all in one piece, they are built in sections and then joined together. The purpose, in Christians words, is to have a rim that is completely free from stress or tension.
In this photo, you can see the outer rim section, and on the right, just the edge of the inner rim joining.
Cylindrical Soundboard Crowning
The second unique feature is the cylindrical, rather than spherical crown. It’s a little hard to show in a photo, but Christian demonstrated with a business card:
This is done for both strength and tonal purposes and is on the uprights as well.