Ongoing‎ > ‎

Stressing the backplate

posted 29 Jan 2017, 07:43 by Peter Grankulla   [ updated 29 Jan 2017, 07:51 ]
To answer a question on Maestronet: Janito's bench about stressing the backplate, the following is in principal on how it's done. This I have done on some violins and it prevents some deformation after the violin is ready and has been used 1-2 years. The images below demonstrates the task. However it is no quick process, but takes up to 2-3 months for it to be successful as maple is very stubborn and wants to go back to its original state. The cork is formed to fit a small area in the middle (more on the soundpost side). The process must be started at high humidity (and EMC in the wood), then it is cycled a couple of times between 65%-10% humidity (again slow process). The stress is successful when the backplate's frequency stays the same for a month or so at the same humidity. The holes in the board are for even MC% distribution. 

This example 175/357 Hz at 10-15% (january 2017). Caution! Don't use hard objects like wood under the plate, or it might crack. The retraction is VERY strong when MC% drops. Cork is preferable, but a folded cloth to fit is also doable. If you start with a high M5 frequency you might end up with a 380-390 Hz M5. I start with 340 Hz at 6% MC


Comments