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Wood Scabbard

March 8th, 2010 admin No comments

Wood Scabbard

Surface Restoration To Antique Metalwork

As antique furniture restorers, we often tend to think of ourselves simply as specialist craftsman in wood and forget that we frequently need to be involved with the surface restoration of the metal items which will invariably form an essential part of the whole piece which has been entrusted to our care.

Restoration to some antique metalwork, often badly damaged and with parts missing or completed corroded by rust, will require specialised metalworking skills beyond the scope of this paper, which is concerned with various aspects of restoration to the surface finish. In the hope that it will be of interest to readers, I should like to share my thoughts and experience of some of the traditional methods of rust removal and simple chemical colour enhancement, to simulate age or blend an area of over abraded or new metal with the existing colour or patination adjacent.

Let us consider the basic requirements for the removal of surface rust, without deep erosion, from antique surfaces. Firstly, it is fundamental that the oxide be removed without affecting any integral brass or bronze work. Secondly, any precipitate formed by the chemical action of the derusting agent must be easily and completely removable without causing abrasion damage to the item. Thirdly, the existing patination, if any, should be affected as little as possible with little discernable colour change taking place. Fourthly, further oxidation should at least be inhibited, positive protection is not a practical possibility if the visual aspect of the item is to be considered. No protective precipitates are either invisible or truly metallic in appearance.

The metalwork to be restored is likely to fall into one of three main categories:

Various hinges, handles and knobs, escutcheons, lock plates and facings. All to be found incorporating or partly formed in brass or bronze and often engraved or surface etched.
Engraved and inlaid plates and mechanisms mounted on antique gun and pistol stocks. Also hilts of edged weapons and parts of their scabbards, again often inlaid with brass.
The many and varied parts of antique clock mechanisms and some early engraved clock dials and other parts.

Commercially available derusting fluids differ in their chemical approach to the problem. There are those containing dilute phosphoric and hydrochloric acids, which dissolve the ferrous oxide chemically, leaving a matt-grey precipitate and those containing styrene-acrylate, co-polymers, which stabilize the oxide forming it into a blue grey precipitate of appreciable thickness.

For the average user wishing to derust general hardware or car parts, the derusting fluids offer an efficient solution to a rust problem. But in my opinion, they are quite useless for treating antique metalwork and can cause irrevocable harm to the surface in many cases. The chemical action produces well bonded precipitates, only removable by quite heavy surface abrasion, an undesirable, lengthy and difficult task should the item be small or of a delicate nature. Yet this will be necessary whenever a metallic finish is required. In the unlikely event of the precipitate removal being successful, the item will then have to be burnished and chemically treated to produce a suitable antique finish. Unfortunately these derusting agents will etch and corrode brass and bronze unless the contact time is brief, thus making their use on multi media items open to serious doubt.

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Georgetown Refinishing & Antique Restoration