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Metal polish

A very fine abrasive with a mild chemical assist. Every use removes metal, which is why polishing a plated or antique item is a one-way decision.

What not to do

Metal polish may damage Chrome plating

Best avoided

The available guidance advises against this.

Evidence

Supported

Sources

  1. Conserve O Gram 10/3: Preparing Historic Motorized Vehicles For Storage Or Exhibit

    National Park Service, US Department of the Interior, 1999 · Government or regulator

    Relied on for: That every polishing removes material, that nickel-plated surfaces can be very thin and are probably already worn thin by previous polishing, and that buffing wheels and powered abrasive methods must never be used on brightwork. (states this directly)

Metal polish is unsafe on Gold plate and vermeil

Unsafe

Do not do this. The risk is established, and it is described below.

A polish works by removing metal, and on plate the metal it removes is a finite layer with base metal underneath. Conservation on another plated surface: powered abrasive methods must never be used, because the plating is probably already worn thin.

Evidence

Strongly supported

Sources

  1. Conserve O Gram 10/3: Preparing Historic Motorized Vehicles For Storage Or Exhibit

    National Park Service, US Department of the Interior, 1999 · Government or regulator

    Relied on for: That plated surfaces can be very thin and are probably worn thin from previous polishing, and that a buffing wheel or any powered abrasive method must never be used on them. (states this directly)

  2. Museum Handbook Part I, Appendix O: Curatorial Care of Metal Objects

    National Park Service, US Department of the Interior, 2002 · Reference work

    Relied on for: That cleaning and polishing remove original metal. (states this directly)

Precautions

  • Test on an inconspicuous area first
  • Check the manufacturer's instructions
  • Wear gloves
  • Ventilate the area

In detail

A metal polish is a suspension of very fine abrasive particles, usually with a mild acid or a complexing agent to help lift the tarnish film, and a carrier that holds the residue so it can be wiped away. Understanding it as an abrasive is what makes its limits obvious. Polishing does not remove tarnish from the surface; it removes the surface, tarnish and all, and a little of the metal underneath with it. On solid metal that is repeatable more or less indefinitely. On plate it is not: silver plate, chrome plate and gold plate are measured in microns, and each polish takes a share of a layer that cannot be replaced except by replating. The silver trade's own conservation guidance makes the same point about antique and hallmarked pieces, where repeated polishing softens engraving and eventually erases a hallmark. Two practical consequences follow. The right frequency for a plated item is as seldom as the appearance allows, and prevention — handling less, storing dry, using anti-tarnish materials — beats treatment. And a polish is the wrong product entirely for a lacquered metal, where the coating rather than the metal is what a cloth would be attacking.

Properties

pH
Varies by product

What works

Why

Aftercare and prevention

  • Metal polish requires the aftercare Chrome plating

    Polish once, then protect — because the reason to protect it is to avoid having to polish it again.

  • Metal polish requires the aftercare Chrome and brightwork trim

    Polish once, gently and by hand, then coat it. A buffing wheel or any powered abrasive is ruled out entirely.

Sources for this page

Sources

  1. Caring for your collections: Silver and plate

    The Institute of Conservation (Icon) · Trade or professional body

    Relied on for: That polishing removes metal, that plate carries a finite thickness of silver, and that frequency should therefore be minimised on plated and historic pieces. (states this directly)

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