FAQs to the Petrof Pianos
How are Petrof pianos protected against extreme climatic conditions?
Extreme climatic conditions are understood to be high temperatures and high air humidity and then causing high wood moisture content.
All currently produced Petrof grand pianos are tropicalised. That means all the wooden piano parts except the action are coated with varnishes that are resistant against infusion of air humidity. Outer polished surfaces are coated with polyester lacquers, other surfaces with polyurethanic or acrylic coatings. There are no open surfaces on the pianos that would enable absorption of air humidity. The Petrof Company steadily takes great care of instruments to insure humidity resistance, continually searching for more effective coatings to protect wood more efficiently.
Petrof upright pianos are produced in two variants. Standard instruments intended to climatic conditions of middle climatic zones have some edges or hidden surfaces without special finish. The instruments that are intended for extreme wet climatic conditions, the Tropics, are Tropicalised as well as all the grand pianos. That means all the surfaces including hidden surfaces are special coated with polyurethanic or acrylic coatings against diffusion of air humidity.
Some pianos have an absolute smooth surface; other ones have a grainy look. What is the reason?
Surface smoothness of the piano soundboard panels depends on the quality of the panels. That depends on their flatness and on the quality and age of the lacquer layer. All Petrof piano soundboard panels and parts are made from perfectly flat and smooth grade “A” materials.
Layers of high gloss Lacquered parts that are then varnished with polyester lacquers are very thick and it tends to reduce its volume (thickness) a little after some time. This contraction is characteristic just for polyesters. Therefore newly sprayed and polished surface is perfectly flat and smooth.
A gentle shrinkage of the lacquer layer can occur after several months or years and its surface can warp a little. Then it can appear not to be perfectly smooth. If these gentle waves become aesthetically unacceptable usually such parts can be re-sanded and re-polished.
What is resistance of the adhesives used in Petrof pianos?
In all currently produced Petrof Upright pianos we use only synthetic adhesives, namely PVAC (polyvinylacetatechloride – white glue) or two component carbamide-formaldehyde glue. All these adhesives have a high degree D3 or D4 water resistance.
Construction-joints of Petrof grand pianos are also glued with the same adhesives as upright pianos, only profiled edges of the cheeks and damper felt of Petrof actions are glued with natural hide glue.
What types of lacquers are used for pianos high polished finishes?
All the polished surfaces of Petrof pianos are coated with polyester lacquers, black as well as white or transparent. Coating suppliers for many years systematically cooperate with Petrof factory. New coatings Used are more elastic to minimize the risk of surface cracks with temperature and humidity loading. Also the adhesion of lacquers to wooden surfaces is improving. Nevertheless it still holds generally that pianos must be protected against direct solar radiation (UV).
How are the brass fittings protected?
All the polished brass fittings of Petrof grands as well as uprights are currently coated with special stoving varnish and they are fully stain resistant. Of course this manner of coated fittings must not be treated with polishing agents containing any abrasives or harsh chemicals.
How does Petrof protect their pianos in shipping?
Petrof uses the most up to date packaging systems; Petrof protects the instruments with great care. The packaging is hermetical sealed. There are siccatives decreasing air humidity and special agents protecting metal parts against corrosion inside the instruments...
What defects of the soundboard affect the piano sound?
The piano soundboard can have several possible defects or imperfections. Piano owners are always interested in how far or if these phenomenon's influence the piano's performance.
Wavy or wrinkled soundboard:
If the piano is placed in space with increased air humidity its soundboard can be slightly wavy or have little bumps along the grain of the soundboard. The deformation is a regular feature of the soundboard. The soundboard is crowned, glued to the wooden frame around its periphery, loaded by the strings from above. It has no chance to increase its crown upon increased humidity while swelling. So it crinkles, forms compression ridges, and compressed itself a little. This compression appears along the grain or glued joints in the soundboard. These symptoms have only aesthetic importance and they don't affect acoustic properties of the pianos, they acre not a defect of the soundboard. Quite the opposes these symptom are the sings that the soundboard was well moisture conditioned to the low moisture content before its assembly to the piano. Such soundboard is bale to resist very low air humidity and there is minimal risk of cracking.
The cracks in the soundboard can develop in consequence of very low air humidity and low wood moisture content (tension cracks) or on the contrary in consequence of very high humidity (compressive and shearing cracks).
The cracks in themselves have no influence on the acoustic properties of the piano, they don't reduce its acoustic output or change the tone color. Simplified it can be said if the ribs and bridges are well glued the soundboard keeps its shape and none of its part generates any unwanted noise, then the cracks have no negative influence on soundboard function. But usually big soundboard cracks are repaired for aesthetic reasons.
Unglued ribs or bridges:
Ribs that have released from the soundboard decrease rigidity of the soundboard’s crown. They can effect deformation of the soundboard and loss of the down bearing. This can be the reason of noises or change of the tone color or decreasing of acoustic output of the piano.
Unglued or cracked bridge or loose bridge pins are also serious problems that decrease the acoustic output of an instrument and they can be a source of noises.