How NOT to Clean Historic Artifacts

Overcleaned brass and wood engine. Undisclosed location.

Overcleaned brass and wood engine. Undisclosed location.

Thorough, safe, or cheap. Pick two.

If the label says “fast, quick, easy, effortless, magic” then it’s probably not good for artifacts.

Or as I’ve been know to say: A cleaning product that works really well? Probably not conservation approved.

And there are reasons for all of this.

The cleaning products and materials that are “easy, quick, and better” are made with things that are often dangerous for artifacts.

Most modern cleaners are formulated to act quickly and reduce labour. To make that happen a variety of compounds are added to cleaners.

These additives fall into into eight broad categories:

■  Strong detergents can damage materials over time. Repeated exposure to detergents can cause textile fibres to degrade. Detergents remove plating and scratch the surfaces of metals. They can also damage finished surfaces and paint.

■  Whiter whites and brighter colours!  Products that promise this effect contain dyes designed to fluoresce in white light, causing whites to be dazzling and colours vivid. Dyes can interact with materials already present in or on an artifact, and obscure or damage original marking and information. They can also degrade over time: changing colour, yellowing, or causing physical damage.

■  Bases or alkalis can be such compounds as ammonia (in window cleaner), sodium carbonate (washing soda), and sodium hydroxide (lye). Sodium hydroxide and sodium carbonate can be found in a range of household cleaners, where they are used for their ability to break up grease and oils. Bleach is made from sodium hypochlorite. These chemicals can attack and degrade organic material and corrode and pit metals. Residues left on artifacts can continue to affect them for years.

■  Acids such as hydrochloric acid are often used in rust removers and bathroom cleaners to remove iron staining, lime and mould or mildew. Citric acid and acetic acid (lemon juice and vinegar) are also suggested as “natural alternatives” for cleaning. But these are to be avoided, since all acids can corrode metals and damage organic materials. Residues left on artifacts can continue to affect them for years.

■  Silicones are often present in polishes and leather cleaners and waxes. These are glossy, man-made materials that are extremely difficult to remove. While they can produce a high gloss shine, they also remain tacky to the touch, attracting and holding dirt on the surface. Once an object has been contaminated with silicone, it becomes very difficult to apply another finish or make adhesive repairs.

■  Fragrances can be anything from naturally-derived oils to completely synthetic compounds. Fragrances can form hard-to-remove films on the surface of artifacts, and they can be corrosive. Natural materials tend to attract pests. Highly scented products can irritate staff and visitors.

■  Bleaches are based on either chlorine or peroxides. Theses compounds are undesirable for their harsh actions on artifacts. In addition, chlorine bleaches can leave a residue causing acids to form on the object surface.

■  Metal polishes tend to be bad news. Most commercially available polishes use harsh abrasive particles to remove tarnish quickly and easily. “Dip” polishes are concentrated acids that strip away delicate surfaces. Liquid polishes often contain damaging ammonia and other undesirable chemicals. Museum-grade polishes are gentle, with tiny abrasive particles. They should not contain acidic or other materials that will leave damaging residues.

Our Canada-wide survey indicates that most small museums and historic sites clean their facilities and collections with a variety of household products. Chemicals combine on surfaces or in the air to form toxic compounds that can harm your artifacts, facilities and visitors.

OK, so most off-the-shelf household cleaning agent are bad for artifacts. What can I use?

Gentle, single ingredient detergents, like sodium lauryl sulfate (SLS) can be used to wash and wipe down objects when it is safe and necessary to do so. SLS is gentle and easily rinsed away, leaving no surface films. It is safe, effective and free from scents, dyes and harmful ingredients.

For glass cleaning a solution of SLS, water and alcohol can be used. The alcohol helps cut grease and leave a streak-free surface.

Current research recommends metal polishes with particles less than 2 microns in diameter. That’s finer than some baby powder. Conservation-grade polishes are also free of waxes and other materials that leave a residue.

The best cloths and wipers are still made from soft cotton flannel and linen. Linen is especially useful for cleaning glass, as it doesn’t leave lint on the surface. Reusable cloths are also much better for the environment.

How can I get my hands on museum-grade cleaning supplies?

Since there was no museum-grade cleaning system on the market we decided to develop our own. You can purchase a variety of museum-grade cleaning agents, polishes and tools  in our store. If you’re a Canadian non-profit you can even sell them and become eligible for free donations from your community.

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For instructions on how to clean just about any historic materials see our comprehensive Artifacts & Facilites Cleaning Guide. And if you have any further questions feel free to contact us.