Organ metal
Organ metal refers to an alloy of tin and lead used to make organ pipes .
Classification
The mass ratio of the alloy is specified as “solderiness”, but the names of the alloys listed here are not used uniformly.
| Solderiness | tin | lead | designation |
|---|---|---|---|
| 16soldered | 100% (pure) | 0% | tin |
| 14soldered | 87.5% | 12.5% | |
| 12soldered | 75% | 25% | "Sample tin" |
| 10soldered | 62.5% | 37.5% | |
| 8soldered | 50% | 50% | "Natural cast" |
| 6soldered | 37.5% | 62.5% | |
| 4-soldered | 25% | 75% | "Lead" |
If the lead content is very high or if the metal pipe is large, a small amount of antimony is also added to increase strength. Due to its mechanical material properties , the organ metal is easy to manufacture and very easy to work with with hand tools. The sound of an organ pipe is influenced by the composition of the alloy. The more tin it contains, the brighter and sharper, the more lead the softer it sounds. Pure tin is only used in exceptional cases. Prospectus pipes are made of alloys with 75% or more tin due to their good polishability.
Manufacturing
Organ metal is still traditionally made using a casting process today: the casting bench is a solid table that must not be warped by the heat, with a linen covering that allows any casting gases to escape. This achieves a bubble-free cast. The casting box is a movable rectangular frame that can be moved lengthways on the casting bench on guides. An adjustable board is attached to the back of the casting box. This allows you to adjust the thickness of the plate to be cast. For casting, the casting box is sufficiently filled with molten organ metal, which is 200 to 300 ° C depending on the alloy, and then quickly pulled over the casting bench. The amount of organ metal that has not been cast is placed in a container at the end of the casting bench and is promptly returned to the casting furnace.
Alternatively, organ metal can also be poured onto a precisely smoothed sand bed instead of the linen covering. The sand has to be re-smoothed before every casting process, which is a bit more time-consuming.
After cooling, the plate is cut cleanly and then planed. In the past, the board was brought to the desired thickness with hand planes, today the planing process is carried out with a special planing machine. For this purpose, the molded disk is clamped to the drum of the machine, the drum is set into a rotational movement and a steel, which is slidably mounted transversely to the drum, cutting the unneeded material gradually away, similar to a lathe machined . This gives the plate a very precise thickness.
The plate is then polished and is available for further processing.
Problems of monument preservation
Silver-white β-tin, which is resistant from 16 ° C to 181 ° C, turns into gray-black α-tin below 13.2 ° C (so-called tin plague ). The tendency to transformation increases with decreasing temperature and can be accelerated by alloying with other metals (e.g. zinc , aluminum ) or prevented (e.g. antimony , bismuth ). Until well into the 19th century, alloys were mostly contaminated, so that the exact composition must always be checked in each individual case. Lead corrosion is a common problem .
literature
- Johann Gottlob Töpfer , Paul Smeets: Textbook of Organ Building Art , Rheingoldverlag, Mainz, Vol. 2, 1957. P. 265 ff.
Web links
Individual evidence
- ^ Table after: Wolfgang Adelung: Introduction to organ building . 2nd Edition. Breitkopf & Härtel, Wiesbaden 2003, ISBN 3-7651-0279-2 , pp. 68 .
- ^ Association of German Organ Experts: Pfeifenwerk , accessed on December 9, 2019.
- ↑ die-orgelseite.de: Orgelbau - how an organ is made , accessed on December 9, 2019.
- ^ Johann Gottlob Töpfer , Paul Smeets: Textbook of Orgelbaukunst , Rheingoldverlag, Mainz, Vol. 2, 1957. P. 273 ff.
- ^ Johann Gottlob Töpfer , Paul Smeets: Textbook of Orgelbaukunst , Rheingoldverlag, Mainz, vol. 2, 1957. pp. 276–277 ff.
- ↑ Andrea Hartwig : Tin . In: Römpp Chemistry Lexicon . Thieme Verlag, as of February 2004.
- ↑ Das Pfeifenwerk (organ information) , private website, accessed on December 9, 2019.
- ^ Final report of the DBU organ project. MPA Bremen, accessed on December 9, 2019 .