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Articles - Wire Tests

 
 

CHRONOLOGICALLY ARRANGED WIRE TESTS

by Edward E. Swenson

One of the most vexing problems for the piano restorer is the frequent changes in the metallurgy of 19th-century music wire. There were dozens of wire makers in the early 19th century and the early piano builder had a wide selection of wire from which to choose. Music wire went through many different transformations in the course of the 19th century. Modern high carbon, cast steel music wire should not be used in restringing keyboard instruments built before 1860. The early piano was strung with iron or low-carbon steel wire, which was softer, more elastic and produced a different sound than modern piano wire. The following chart shows the increased percentages of carbon and the greatly increased tensile strength of music wire from 1827 to 1913. The load capacity of the wire is measured in Newtons. It is also interest to note that the wire used by Steinway at the turn of the century has a much lower carbon content and yet a higher tensile strength than contemporary Rslau wire which one might elect to use in stringing an old Steinway. The strength of the wire does not necessarily determine high quality. A high percentage of sulfur (anything over .030 percent) is usually regarded as a metallurgical defect in the manufacture of wire.
Wire Sources Diameter (mm) Min Load Cap. (Newtons) Tensile Strength (N/mm2) Carbon % Sulfur %
Graf fortepiano #1594 (Vienna, c. 1830) .772 / .777 560 1189 .3150 .015
Graf #1594 2nd test .911/.921 530/535 804/812 .095 .007
Graf #1594 3rd test .754/.769 440/445 967/978 .125 .010
Graf fortepiano #2627 (Vienna, c. 1838) .886/.885 530/540 882/898 .077 .008
Graf #2627 (brass wire) .995/.940 610 830 - -
Bösendorfer fortepiano #167 (Vienna, c.1840) .790/.802 580/590 1170/1190 .370 .045
B.G. Wire (Vienna, c. 1840) .730/.735 400 950 .0553 .0044
Broadwood square #15793 (London, 1850) .993/1.005 900/905 1148/1155 .45 .035
Chickering (Boston, c. 1850) 1.150/1.190 1815/1910 1690/1780 .72 .052
Bösendorfer #3881 (Vienna, 1851) .810/.814 1070 2066 .72 .010
J.B. Streicher grand #6493 (Vienna, 1863) .744/.749 890 2036 .46 .008
Bechstein grand #981 (Berlin, 1864) .945/.947 1610/1640 2291/2333 .81 .017
Steinway (NY) #89867 (1897) 1.130/1.148 2540/2560 2490/2510 .740 .032
Steinway (NY) #160445 (1913) .965/.969 1860/1925 2530/2620 .770 .034
Steinway (NY, 1959) .938/.943 1680/1700 2421/2450 .74 .010
Malcolm Rose Type B .693/.695 340/360 900/950 .12 .018
Malcolm Rose Type C .893/.900 720 1140 .45 .022
Malcolm Rose Type C (Control) .900 720 1132 .4380 .0240
Christopher Clark Cluny, France. Modern harpsichord wire .921/.929 1580 2351 .805 .011
Giese Wire Co. sample wire c. 1975 1.119/1.125 2410/2380 2437/2407 .915 .0135
Röslau wire - sample wire c. 1987 .900 1457 2290 c .85 ?

 

About tests 1,2,3,4,5,6,8,9,10,11,12,13,14,15: These test wires were fragments of old, original strings which had already been under tension.

Tests wires 1,2, & 3 are different original strings from the same Graf fortepiano.

About Test 7: 'B.G.' wire found in a drawer next to the keyboard of an early square piano built by Joseph Knamm in Vienna (c. 1825]. This test result is interesting because the wire has never been under tension. The test shows that this iron wire has a very low carbon content and a correspondingly low tensile strength.

About Test 11: Original wire from a J. B. Streicher grand piano selected at the factory by Johannes Brahms for Amalie Bauer.

About Test 12: Original wire from a grand piano given by the Bechstein company to composer Richard Wagner.

The author thanks Dr. Hans Joachim Krueger of the Roeslau Stahl- und Drahtwerk for his help in preparing these test results.

© Copyright 2008 Edward E. Swenson, MozartPiano.com
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