Restoring a pedal harp
Miguel Zenker Escuela Nacional de Música, UNAM PAPIIT Project IN403197
Performed: Victor Hugo Mendoza Sánchez
Dorado:
Advisory: Chavarria and Salvador Soto Flor
held: Salvador Soto and Hugo Mendoza
Presented in Paracho, Michoacan. Third Meeting
Music, Wood, Violin, 2006.
An Interdisciplinary Meeting.
22 al 29 April 2006 Article revised and expanded
Introduction
musical instruments in the concert activity are high quality instruments that guarantee a good performance of the musical work of the profession. Many of them are ancient instruments that should preserve for future generations. Are classified as cultural property.
One of the reasons why the instruments are restored, mainly in the middle of musical practice, is that the instrument is a widely used and in order to continue working in concert life, so much for the support of each day, you must have a quality instrument in good condition to ensure to meet the challenges of career demands. As the instrument
an object of use, the instrument is damaged or at least wears in several of its components. It is therefore necessary to conduct regular maintenance to ensure its smooth operation. But there are other factors that cause it to deteriorate. His move, for example, often resulting from slight knocks and scrapes to serious detriments in your state. The environment also results from influences are not noticeable in the short term, to severe structural damage and / or state. Is not the same hold an instrument in a cabinet with controlled temperature, humidity and light, to be transported between environments with significant changes in these factors. Other factors may also influence their status, for example, the string tension. In a museum, the instrument, to be monitored, and become aware of distortions in its parts, such as the emergence of cracks or abnormal curvature in the tops keyboard instruments, impairment can slow down the string tension. A tool of use is more difficult. Changing strings, strings with less tension with the same pitch, for example, can cause changes in the sound that professional musicians are not acceptable. When this happens, the economic factor becomes a decisive factor. Many times, having no financial means to an instrument change, the restore may be the alternative.
As time progresses, however, has created a growing awareness that restoration necessarily imply an alteration of the original. An instrument to intervene, therefore, requires an analysis of the reasons that have to be restored, in contrast to the results and the implications for him, the proposed work.
In summary, we state the following principles of restoration:
• All restoration alters the original. That is why preservation is preferable if one wants to preserve the integrity of the cultural, ie the instrument as the original document.
• The restoration is valid, if you decide to play the instrument and does not represent an exceptional value. If this is the case, it requires substantial grounds for carrying out the restoration.
"Alternatives? • Conservation performs
essential work to avoid possible deterioration beyond the current state of the property and preserve its integrity. The instrument, in most cases, remains to be played.
• Restoration, from an ethical perspective, it performs the work necessary to return the instrument to a state where you can touch, considering the change, while respecting the original as possible.
The problems that arise, in essence, are:
• A restoration with respect to the maximum of the original is very expensive.
• The musician, generally can not afford the costs.
• There is no instance or any institutional regulation in our country, that will support the musician for a restoration intervention that meets all the requirements.
The consequences: the restoration work is done by lowering the costs to the fullest, carrying out tasks that alter parts of its originality beyond what is desirable, because it is less expensive.
object Here is a Pedal Harp Lyon & Healy, with serial number 787, according to the number at the base of the instrument. Data from the early twentieth century (1915-1920 [1] ). Is 47 strings, with the body extended at the top in the bottom where the bass strings are inserted. It is golden in the column, base, console lid. The harp is in a Mexican harpist.
Fig 1 The pedal harp and parts
Description
lid lid (Fig. 1, 10 and Figure 2, 10 and 11) consists of two layers of wood Picea spp .. The first (11) is 2 mm thick, with longitudinal fiber. Is what is visible, painted and decorated in gold. The second (10) is 9 mm at the widest section and tapers to 2.5 mm thick at the narrow end and is ready with the fiber in the transverse its length. Both are stuck together. State
The lid of this study showed a rise of 42 mm without tension of the strings (Fig. 2, red line), which has serious implications for the pitch of the instrument [2] . The outside of the cover sheet (Fig. 2, 11), was approximately 20 split. The inner layer of the lid (Fig. 2, 10), was approximately 90 split. The console had a twist or deflection of the plane of 3 degrees, which caused the central octave forks barely touching the strings.
Figure 2 Cut Box resonance, with deformation of the cover (red lines) lower section
Figure 3 Section of the soundboard, top section
Top
Structure
The outer layer, a sheet of 2 mm in thickness had approximately 20 split. The exterior was covered with a varnish soluble in alcohol and decorated with a fillet and tendrils [3] gold.
Figure 4 looks inside the inner plate with one of the longitudinal sections along the brace.
inside lid (inner layer) had about 90 cracked and some ripping done with the brace as shown in the image (Fig. 4). Outer and inner layer were prepared with perpendicular grain. In a brief calculation of the separation in each of the slit of the inner layer, made with digital vernier, the total loss of material shrinkage accounted for one-and two centimeters.
Analysis of possible processes
To paste the cracks from each of the layers, it was necessary to separate the top of the shell and the lid parts together without damaging any of them. We evaluated three options:
1. The method of wedges and alcohol use accounted for too long spatulas to manipulate and control the pressure and its progress. Apart this, the differences in the thickness of each layer representing a danger that the outer layer is too thin to withstand the pressures and inevitably break.
2. The method of moisture represented a safer, despite the risk of moisture penetrating the outer layer and caused the detachment of the varnish and gold. This danger could be controlled with a jog in the humidification of glue (animal glue). This method was not out of reach in the tool and material resources available and would have meant the salvation of both original layers of the instrument. However, represented an investment of time and moisture control progress slow that it was not, unfortunately, linked to the budgeted income for the work of the harp.
3. The third method was to save the outer layer and sacrificing the interior, replacing it with a new one. Represented a move much faster on the job and full security in the rescue of the thin outer plate decorated with gold. Finally it also meant, in regard to the inner layer, the replacement of lost material not only in the longitudinal to the top (perpendicular to fiber), but also the replenishment of material in relation to the thickness of the layer, thus, replacement of both the physical stability (resistance) of the cover and the sound of instrument.
For economic reasons it was decided by the third method.
process is a process of restoration with full respect for the integrity, the lid should be separated from the "shell" with slow processes to take off belts (Fig. 2, 19, 12 and 20) and separate the layers of includes the top, with the possibility of extracting each part without deterioration. This process is slow, too risky and has a considerable investment of labor, was replaced, after finding that the glue used was animal glue on the strips off the spatula and alcohol. The bands, with the fiber in every way possible, unless the longitudinal, not withstand the tensions that knives offered for release, so that large parts were separated into pieces.
After removal of belts, screws were removed (Fig. 2, 28) that secure the lid. For this separation, we used the same method as in the previous process. In this case, the irregularity of the contact surfaces, ie the shell and internal contrafajas (Fig. 2, 28) greatly facilitated the work.
The same method was applied to detach the central strips of reinforcement (Fig. 2, 16 and 17). These strips of wood concise (whether the exterior and the interior maple), Picea spp opposed to top, caused the most of the chips to fall off the top, being attached to the hardest woods. Consequently, ribbons, after washing, remained intact, so that the exterior could be reinstated later at the top, using your guide to drill holes and cover with the bar inside, which was replaced by its deformation in the the bass section. In this way the distances and thicknesses obtained original post holes for fastening the ropes.
Boards support in the wash and paste cracked and for pressing the top
To work with the lid and the console, were developed for each, two plates of plywood 19 mm thick, of equal size, one of which was reinforced with strips of wood strong enough to withstand the pressing of parts (Fig. 11 and 12) and keeping the workpiece flat during pressing. This unit is reinforced lined on one side, after rectifying it with squeegee, a self-stick mica plate. The counterpart is lined, also on one side, first with cork 4 mm thick to allow the distribution of pressure uneven surfaces to press the plates assembled on top and console. Later he covered the cork with aluminum foil to prevent the cork from sticking to the parties that were striking (see Figures 12, 19, 42 and 43).
Working with the inner layer
The inner layer is devastated first gouging. Subsequently brushed with small brushes for violin bends down to tenths of a millimeter from the surface of contact between the two layers, ie, until a translucent layer of wood between perceived that the figure of the wood of the outer layer . For this study used a pressing plate for the top, covered with self-adhesive mica, which was deposited on the outer surface of the outer layer, thus being protected during the work. Figure 5
roughing the inner layer.
Once deposited the outer plate of the cover with his face painted and gilded on the deck mica, is placed at the contact surface wet cloths to hydrate and thus soften chips and glue. When it was found that the chips came off easily by inserting a spatula between chips and veneer, it was removing the chips and washing the tail, beginning with the larger end, until the narrow end of the sheet (Fig. 6, 7 and 8).
Figure 6 Release of chips and cola wash exterior veneer
Figure 7 Release of exterior veneer chips
Figure 8 Appearance of the exterior sheet in the process of releasing waste from the inside.
With separation cover and reinforcing strips, both the central strip (Fig. 8) as the banks were damaged to such an extent that the plant did not survive in much of its journey. Thus was completed separate, later to reinstate like the banks, thus providing the missing plate lost the natural shrinkage.
After removal of splinters and glue veneer is cracked proceeded to wash with warm to hot, depending on the strength of the dirt, and soft brush, taking care not to damage the varnish and wood.
During breaks in the process of washing the cracked plate is pressed lightly, with pressure on both the surface and sides, either wet to continue after the removal of chips, or, later, to allow slow drying of the piece, keep the flat and closed cracks. Figure 9
ford cracked exterior veneer
Figure 10 Appearance of exterior veneer cracked after washing
Preparation for bonding veneer cracked
For the bonding of the cracked was used previously prepared mica plate. On the mica plate is placed a sheet of bond paper, larger than the slit to stick to absorb the excess glue to flow from the slit. The plate was deposited on the surface bond paper painted on the mica and the region of the slit on the paper, taking care that is completely covering the slit. The sheet was pressed a few inches from the slit, fitted with a cork block to distribute the pressure and aluminum foil to prevent the cork from sticking to the excess glue. The block should preferably be longer than the slit itself. Figure 11
tracing the outline of the mold plywood ¾ "thick lid for pressing. Stuck on this mold the outer layer cracked and reinforced and the original outer layer with the new inner layer.
Figure 12 Diagram of bonding the outer layer cracked, side view Figure
Bonding 13 cracked outer layer, lateral view.
Figure 14 Pasting outer layer cracked, front view.
Parallel to the edge of the plate, the other end of the slit and the mica plate is pressed a block of withholding. Between the block and the plate is placed several spots in pairs, both at the same angle, so that conflicting, press always parallel the edge, closing the slit. For the plate does not lift the pressure of the wedges, placed several blocks of cork and aluminum pressed, first pressing slightly to make the plate is flat, but with the possibility that the plate could be moved to action of wedges, and close the slit, always verifying that the outer surface of the plate is at the same level. With the flat and the slit closed, another block was placed on the cracked pressed to metal surfaces remain at the same level. Insurance and the slit is closed, more pressure is finally applied to blocks of intermediate pressing. (Fig. 12-14)
This process was first "dry", without using glue, to make sure you have all the parts needed to seal up the slit. Subsequently disassembled everything but the first blocks: the first pressing and holding. Applied and the tail were placed in other parts the same order as described in the preceding paragraph always ensuring that the outer surface of the plate is on one level and the slit closed.
After drying the tail of the cracked, fell off presses and wedges and blocks were removed. The plate is carefully removed (as the tail, to penetrate the Bond role, is set to twice a mica plate pressing) and turned on Bond paper plate stuck to the plate. With warm water, wet the paper until the lift it off the plate. He then carefully washed with excess glue varnish spread over the plate and dried thoroughly with a dry cotton cloth. The plate was ready for bonding of Next cracked, for which the process was repeated from the beginning. In the event that not enough time to hit more cracked, the sheet was pressed with less pressure on the press plate. Thereby allowed to dry the last wash of excess glue, then water can soften cracked tail just pasted, and kept the piece flat.
Figure 15 cracked exterior veneer glued to the bond paper still attached.
central Gaza. Attached
all cracked, proceeded to join the two halves of the plate with a central strip that had been damaged by the separation of the reinforcing strips and then replenish outer bands are the holes through which screws are inserted to secure the cover to the body resonance of the harp. The replacement of material shrinkage, was distributed in both field and central strips. First
chips were removed from the original central strip were still attached. After each song was rectified to obtain a flat surface, and finally brush each half sheet on the underside at an angle of about 22 °, and leave a corner vertex of which coincided with the edge of the outer surface of the plate. Later she brushed a piece of spruce, the closest thing to the original wood veneer, leaving a little thicker than the plate and another corner of the same angle that was given to the plate. This strip was glued, corner to corner, the original sheet. (Fig. 16-18)
angle of 22 ° is intended to increase the contact surface (by pasting against chamfer chamfer), and thereby increase the bond strength to the tension exerted by the strings to be tuned instrument. An assembly at 90 °, depending on experience, usually reopens in time for the tension once tuned the harp.
central graft
central graft assembly diagonally to avoid opening with the string tension. Figure 16 Reintegration
the central strip with new wood. Front View Figure 17
Reintegration of the central strip with new wood Rear View
opposing chamfers 22 °
original sheet central Gaza
new outer side
varnish Figure 18 Diagram of the reintegration of the central strip with new wood
outside Gaza
The outer strip was treated similar to the inside border. The difference is that the outer edge was curved, while the interior was straight. Thus, the wood to the outer edge had to be chosen, cut and assembled in parts, according to the curvature of the top and along the grain of the plate. Thus, original and new sheet metal bands were a chamfer of 22 °. The chamfer on the edge of the sheet and the new bands had to assemble perfectly. Once assembled
strips with veneer, brushed those with thick and profiled, leaving space for wood glue left over the plate with the inner layer.
Cover, inner layer
To replace the inner layer was chosen Picea spp with a structure similar to the original. Is flipped with a thickness more than necessary and assembled the parts needed to build the layer (Fig. 20). Already assembled, brushed with a thickness 1 / 10 larger than the original, taking into account that the cap had thicknesses, had raised more than normal, which means that it was not strong enough to string tension [4] also losing material throughout its 80 years of life.
for bonding the two layers were used for pressing the two plates above (Fig. 19), placing the plate, his face painted on the mica, the inner layer on the metal and counter top with cork and aluminum. The result is shown in Figure 26.
Figure 19 Strengthening the press plate covered with mica.
Figure 20 Cover, inner layer. The arrow indicates the direction of the fiber. Paste
bracing and battens
First stuck to the inner brace over the top, according to the dimensions of the original, plus 10% (approximate) increase in thickness. Subsequently developed and posted its two harmonic bars in the same position as the original. The shaping of the rods was performed after the glue had dried. Then he hit the bar are original, taking care that both ribbons are centered over the top and finally varnished the inside cover with shellac, as was the original. (Fig. 21-25 and 27)
Harmonic bars
Rebar inside cover Figure 21. Location of bracing on the interior surface of the lid. The rebar inside the cover is already attached.
Figure 22 Pasting a harmonic bar. Figure 23
hit the bars cover
Figure 24 Lid with attached bars. The bars are still not profiled.
Figure 25 Profiling and cut the cash bar for metal angles that attach the lid to the base.
Figure 26 cover edges, inner layer central strip and returned. Presentation on the soundboard and part of the base of the harp.
Figure 27 Replacing the original exterior brace with the holes and eyes ivory for strings.
Figure 28 Verifying the longitudinal curvature of the lid.
Figure 29 Verification of the longitudinal curvature of the cover, detail. Paste
cover the shell
To paste the cap was first necessary to rectify its surface contact with the soundboard or rather "the shell." This is made sure that the longitudinal curvature of the lid does not alter the original, dictated by the flow of the edge of the shell and its contrafajas. The measure of curvature, provided at the factory in 1998, is "more or less" 7 / 8 ", equivalent to 21.6125 mm. The curvature achieved was 2 mm smaller which falls within the "more or less" or, which is also possible, but I can not get information on the factory, the curvature was slightly lower at the beginning of the century, when they built this harp. (Fig. 28 and 29)
Adjusted cap is made the holes for bolting the cover to the box. Subsequently glued, pressed and screwed, removing the press one by one as each screw was inserted. (Fig. 30 and 31)
Figure 30 holes for screw cap
Figure 31 Bolt cover glued
After the cap was adjusted according to its silhouette edge of the shell, to glue the strips as and upper side, cut and planed and assembled, and the side and also folded (Fig. 32-34). The latter process with respect to the top was painted strips. First we applied a base of boiled linseed oil, because they are parties not involved in the acoustics of the instrument and give it with linseed oil a more consistent with the original, and finally applied the shellac.
Figure 32 Assembly of two sections of exterior fascia
Paste
Figure 33 outside a strip
Figure 34 Paste an exterior fascia, detail
[1] The Lyon & Healy company could not provide more accurate data. This may cause the fire that happened in Chicago in the late nineteenth century, in which much information was lost.
[2] The harp is designed to offset, through the fork (Fig. 1, 7), arising out of tune by the deviation of the curvature of the cap perpendicular to its length, which in turn gives a deviation from the original curvature in the longitudinal direction. This deviation from the prolonged tension of the strings that represent the modern harp, more than half a ton. However, to exceed the allowed deviation cap, forks are no longer possible to counter this deviation. It is necessary, therefore, return the transverse curvature of the cap to its original state, which is without tension of the strings, flat, lengthwise, curved.
[3] Meyer, FS, Handbook of Ornament, G. Gili, Mexico, 1996
[4] The tensile strength of the strings is an issue that ultimately was not entirely clear. It requires a research project on the mechanical properties of the wood used in building the tools to further clarify this point. On the one hand, the resistance depends on the thickness of the pieces, but also depends on the mechanical properties the piece itself. Two timber of the same species may have different properties, which, for the same use, should have different thicknesses, as can be in the carving of two funds for violin of different hardness and density.
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