In certain areas of the production the use of computer controlled machines is better than using handcrafted techniques; in particular in areas where only precision is essential. The star-shaped back-frame as an example is cut using such a machine.
However, when it comes to assembling single pieces together, to get the soundboard vibrating, to regulate, to tune and finally to voice the piano, then nothing is better than the experience of our craftsmen, who have worked at GROTRIAN for many years.
The wood for the various parts of the instrument which must be strong and highly stable are made from solid red beech tree. This applies for example to the grand piano legs and to the sound board bracing. The sound board itself is made of carefully selected mountain spruce with a minimum age of 200 years. The annual rings of this wood are extremely thin, which makes the entire sound board homogeneous.
The star-shaped back-frame, patented by GROTRIAN in 1905 already, has been used since the beginning of the 20th century because it is regarded as the best construction for absorbing tension. The shaping and drilling of the back-frame, the case and the lock-rail is conducted with a CNC-machine providing the utmost precision, essential during this production process.
GROTRIAN uses a unique rim press machine for gluing together the different layers of timber for a grand piano. This machine works with high pressure at a temperature of 90°C. For gluing and veneering special water-resistant 2-component glue is applied, this guarantees reliable bonding in all climate regions across the world.
The combination of an iron frame and the wooden back-frame resists a tension from the strings of more than 20 tons and gives all GROTRIAN instruments an extraordinary stability. The special feature of a GROTRIAN iron frame is the closed and continuous moulded edge, as well as the precisely calculated strengthening stars within the frame itself. These iron frames are cast by a specialized supplier, then drilled and shaped before the hitch pins are applied. After rigorous controls governing the quality of the frame the surface is then refined at the GROTRIAN factory.
All spray rooms in the GROTRIAN factory use cutting-edge technology and minimize every kind of emission. They meet the rigorous environmental standards required in Germany, which ensures a healthy work environment for our staff. Many parts of the case are sanded, brushed, sprayed and dried in the electronic screened cast machine. The lacquer is applied almost without wastage, which again protects the environment. GROTRIAN offers its pianos in classical black polished and in other colours or veneers according to individual requirements. For example in walnut, cherry, rosewood and yew wood to name but a few.
After the preparation of all the components the piano is gradually assembled. The back-frame, the soundboard, the ribs and the bridge are glued together. The iron frame is fitted, the holes for the wrest pins are drilled and the strings are mounted to the piano. Later the instrument’s frame is cut to the correct shape and the playing table made of steel profiles is mounted and becomes the base for the keyboard and the action. Afterward this the action and the keyboard are installed and the instrument is regulated, tuned and voiced several times. The whole procedure requires the highly developed skills, calm hands and the exquisite hearing of our piano builders.
One of the last steps is that the playable but ‘raw’ pianos receive their case. Fixing the case at the last moment requires precision to the highest degree, but also allows flexibility in the production process. The advantage is that only at the very end does a decision need to be taken about which surface the piano will be finished with. In this way it is possible to build continuous quality and at the same time to react quickly to specific customer requests.
Before an instrument gets its final factory approval, our head master craftsman examines it carefully, double checking each manufacturing step to ensure the quality and tone of the instrument. The Managing Director himself then carries out a final inspection before the piano is allowed to leave the factory. GROTRIAN was the first piano manufacturer worldwide to receive the quality management certificate DIN ISO 9001, an indication of our dedication to perfection.