Applicazione dell'impregnante proteico all'interno tavola

Описание: ⬇️⬇️ (English translation of the Italian text) ⬇️⬇️
0:00 - Application of the protein size inside the top plate
0:12 - When you hollow the inside of the top plate, the release of the internal tensions of the wood causes an inevitable deformation of the gluing surface and the external profile of the arching, which will change its transversal radius of curvature, making it flatter. Applying a protein size inside (casein in my case) creates a surface tension that allows the initial geometric conditions to be restored, with a consequent increase in stiffness highlighted by an increase in the frequency of Mode 5. This increase in frequency is often attributed to the stiffening power of protein impregnants, but I'm more inclined to think that it is simply due to the restoration of the initial radius of curvature, as a more curved radius creates a stiffer structure than a flatter one. There may also probably be a contribution of casein in increasing stiffness, but considering the minimum quantity applied (the increase in weight is practically irrelevant, at most 0.1g) I consider it only marginal.
0:51 - Finished arching before hollowing the inside: initial conditions of the undeformed gluing plane and curvature radius
1:04 - Top plate with finished thicknesses and cut f-holes: deformations of the gluing surface and of the transversal curvature radius
1:37 - Using a small sponge, apply a very dilute aqueous solution of casein (4% concentration) to all internal surfaces. Apply it sparingly, distributing it evenly, squeezing the sponge well so that it does not drip, and taking care to avoid stagnation on the gluings (center joint) which are sensitive to water and alkalis. This preparation, in addition to creating a surface tension that restores the correct geometric structure, has the purpose of consolidating the surface fibers of the wood and making it less sensitive to fluctuations in ambient humidity, limiting its absorption. It also has a disinfectant and antibacterial effect due to the presence of ammonia and calcium hydroxide (lime water).
4:54 - Applying casein will cause a strong deformation of the plate, due to water absorption. This shouldn't worry because once the water has evaporated, the plate will return to its initial state without problems. Contrary to what one might think, it is absolutely necessary to avoid blocking the board on its outline with the intention of containing these deformations because in this way all the tensions would concentrate on the center joint, with a serious risk that it would come unglued.
5:56 - Let it dry for a few hours and when the surface is dry it is advisable to heat the plate moderately with a hair dryer to facilitate complete evaporation in depth. The complete hardening of the casein will require about 48 hours with ambient humidity not exceeding 50%, if the humidity is higher it is advisable to use a UV box to ensure complete hardening.
7:06 - Once completely hardened, all the deformations will have disappeared and the plate will have recovered its initial correct shape, which can be easily verified by placing it on a plane and checking that the transverse radius has returned to the one set during the arching making process. Another confirmation of complete hardening is given by the frequency of Mode 5, which must be increased by about 1/4 of a tone (about 10 Hertz) with respect to that of the plate before applying the casein.
8:24 - Finish the inside by sanding very lightly with horsetail (or other very fine sandpaper if you prefer) to remove the surface roughness caused by the swelling of the wood fibers

10:21 - Recipe for the preparation of Casein:
Casein powder: 1.5g
Distilled water: 15g
Leave to soak overnight to make the Casein swell. Add 4.5ml of Ammonia (30% solution) little by little and mix well until everything is dissolved. Add 18ml of lime water (saturated calcium hydroxide solution), mix well, and leave to rest for a few hours.
Concentration at 4% (water 37.5g - Casein 1.5g)
Dilution ratio 1:25 (1 part Casein: 25 parts water)

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