Short answer. The original National Park Service (NPS) documents support comparing spring-metal weatherstripping as a general option with the rolled-zinc interfaces used in one replacement-sash project; they do not establish a brass-versus-zinc alloy comparison. NPS Preservation Brief 9 says metal strips or new plastic spring strips may be used on wooden-window rails and, if space permits, in channels between sash and jamb. source In NPS Windows No. 6, the Lawrence-Wentworth House project instead used rigid strips made from rolled zinc for its new replacement wooden sash, in preference to spring-metal and other alternatives. source These sources do not establish the alloy of an unidentified surviving strip or make the two interfaces interchangeable.
Compare the documented interfaces—not assumed alloys
| Record without alteration | Spring-metal option: what remains unknown? | Rolled-zinc example: what does the NPS project show? |
|---|---|---|
| Location | Brief 9 lists unspecified metal strips or new plastic spring strips on rails and, where space permits, in sash–jamb channels; it does not establish a spring-metal-specific location or fit. | Does the visible location resemble the documented head/jamb/sill flange-and-groove or meeting-rail double-hook interface? |
| Mating surface | Photograph any remaining contact surface and identify which sash can move; do not assign an alloy from flex alone. | In the cited replacement-sash project, grooved rails/stiles fitted over a flange, while two hooks interlocked at the meeting rail. source |
| Documentary match | Does an original project record identify a spring-metal product or simply a strip location? | Is there direct building-specific documentation for this geometry, or only a resemblance to the separate NPS case study? |
The head, jamb, sill and meeting-rail details above describe the NPS replacement-sash case, not a universal prescription for historic double-hung windows. source Neither NPS document in this comparison establishes that a spring-metal strip in another window was made from brass or bronze.
A non-destructive inspection worksheet
Start by numbering the individual window and marking upper and lower sash. For each of head / left jamb / right jamb / sill / meeting rail, take a broad context photo and a close-up at the same orientation. In your notes distinguish (a) strip still present, (b) groove or fastener trace only, (c) no surviving evidence, and (d) area inaccessible without dismantling. Record a separate answer for each component; do not flatten an entire opening into “zinc” or “brass.”
Next, compare the observed interface to publisher drawings while keeping project provenance visible. If the surviving part flexes, record that as observed behaviour, not a metal-alloy diagnosis. If all you have is an empty groove, record former mechanical attachment suspected; original material and mating geometry unknown. The available NPS documentation does not establish that a particular surviving strip in your building is brass, bronze, zinc or even original.
What counts as a useful result?
Evidence-backed: a local historic specification, provenance image or retained part that supports the original arrangement. Candidate: a shape resembles an NPS example but original material and installation era are not documented. Stop: new groove-cutting or replacement would remove historic wood, affect sash operation, or guess at a missing mating half. Choose conservation assessment in the latter two cases before choosing a product.
For the general spring-metal profile family, consult the dated existing /profiles/spring-metal-tension-strip/ reference . This article instead compares what the two cited NPS sources actually document. It does not identify a surviving material as brass, prescribe a spring-bronze position, reconstruct a missing zinc part, or assert dimensions, interchangeability, costs or universal conservation approval.
Official sources and precise sections
- NPS Preservation Brief 9, John H. Myers, 1981, United States,
PDF index 5–6 / printed pp6–7; Weatherization— https://www.nps.gov/orgs/1739/upload/preservation-brief-09-wood-windows.pdf - NPS Preservation Tech Notes, Windows No. 6, Charles Parrott; 1983 project, publication year not independently fixed,
PDF index 1 / printed p2; Fabrication and Installation final column— https://www.nps.gov/orgs/1739/upload/tech-note-windows-06-replacement-wood-sash.pdf - NPS Preservation Tech Notes, Windows No. 6, Charles Parrott; 1983 project, publication year not independently fixed,
PDF index 1–2 / printed pp2–3; Fabrication and Installation, Figure 2— https://www.nps.gov/orgs/1739/upload/tech-note-windows-06-replacement-wood-sash.pdf