Back

Basic Care Instructions #9: Removing Silver Tarnish With Aluminum Foil & Baking Soda

 

****

BASIC CARE INSTRUCTIONS #9: Removing Silver Tarnish With Aluminum Foil & Baking Soda

****

 

This is the 9th in a series of newsletters on common care instructions for domestic items and materials most often seen in antiques and vintage textiles, including but not limited to housewares and clothing. I hope this care information is helpful to you

You may well know a lot more about the care of domestic items than I can tell you here, but it's nice to have all this information in one place. So at the risk of boring you, this newsletter goes into some detail.

This newsletter covers techniques for removing tarnish from metals, particularly silver and gold, and the basic chemistry behind tarnish. The information here is basic information relevant to all metal. Future issues will cover wood repair, polishing and finishing, and cotton and silk knits, outerwear, sweaters, shoes, trousers, jackets, fine leather goods, and lingerie. 

See our issue BASIC CARE INSTRUCTIONS #1 for information on how to read care labels you may find on vintage fabrics (and you should follow them if you do find them!). All previous newsletters in the series can be found in our library and in the newsletter archives.  

**** 

If you have any objects made from silver or plated with silver, you know that they don't stay shiny; they gradually darken and eventually turn black.  This is because the silver interacts with sulfur-containing substances; these are mostly airborne, but they can also be introduced through use, such as drinking wine from a silver goblet.  With a little knowledge of chemistry, you can restore the shiny silver and reverse the tarnishing reaction. 

****

 

****

The silver combines with sulfur and forms silver sulfide, Ag2S (see the equation below).

2 Ag  +    S   → Ag2S
silver + sulfur → silver sulfide


To get the hang of this process, I suggest you first try the instructions on a single piece of plated or solid silver, preferably bigger than earrings and about the size of a teaspoon, essentially something big enough so you can easily discern the effects as they happen.

 

 ****

****

First, let's define terms so you know what's actually happening when you see silver turn black.

**** 

What is "tarnish"?  Tarnish is the result of a chemical reaction, specifically tarnish is a thin layer of corrosion that forms over metals such as copper, brass, silver, aluminum, and magnesium, as their outermost layer undergoes a chemical reaction. 

What's a "chemical reaction"?  A chemical reaction is a process that leads to the transformation of one set of chemical substances into another; it's a change that occurs when two or more substances combine to form a new substance. You're a "chemical reaction", and you're "undergoing chemical reactions" all the time.

**** 

**** 

Oxygen and sulfur compounds mixing with moisture are the most common cause of tarnishing. Individual body chemistry also varies and that's why the metals you wear may be more inclined to tarnish, or tarnish more quickly, than that same metal does when someone else wears it. Chemicals in perfume, hairspray, deodorants and cleaning materials like chlorine and detergents also influence tarnishing, and constant exposure to them can tarnish even the higher 14 and 18 karat gold alloys. No metal is impervious to tarnish, however some metals are more resistant to tarnish interactions than others.

 Exposing even highly resistant 24 karat gold to a corrosive atmosphere can cause it to tarnish, so I don't recommend leaving it lying around near an active volcano because there's too much sulfur in that atmosphere!  

****

****

Food items with high levels of acidity or sulfur (i.e., sulfured apricots) can cause tarnish; onions, fruit juices, spices, and pickled items are notorious for metal interactions that cause tarnishing.

If you want to cause tarnish, rather than remove the tarnish from a piece of silver, follow these instructions:
In a sealed bag or container, place the silver together with hard-boiled eggs (peeled and sliced) or real mayonnaise for at least 24 hours. The sulfur released by the eggs or real mayonnaise will tarnish the silver.

The point I'm making is that your individual body chemistry, your lifestyle, and your environment, including your altitude in relation to sea level, all actively affect any metal you use or wear.

****

****

Incidentally, gold is best cleaned by diluting some non-phosphate dishwashing liquid with water, at the ratio of 3 parts water to 1 part dishwashing liquid, and wiping the tarnish with the mixture using your fingers or a cotton swab, and air dry.  Don't use toothpaste or baking soda on gold alloys; they're too abrasive for gold.

Like rust, tarnish only happens to exposed surfaces and not to underlying layers, and thus it's referred to as "a self-limiting surface phenomenon".  Only exposed top layers of metal will react, and the results of this reaction, called "tarnish", coats the top layers with a thin film, ranging in appearance from just dulling the metal's shine to vivid green or black.

The color of tarnish varies depending on the metals involved; studying the color of tarnish on old metal is one way to discern the constituents or composition of various old alloys.  

****

****

When silver objects are exposed to pollutants normally found in air, they gradually become dull and discolored. This darkening of silver is called tarnishing. Tarnish, however,  doesn't always result from the sole effects of oxygen in the air. Silver, for example, needs hydrogen sulfide to tarnish, although it may tarnish with oxygen over time. As stated above, silver interacts with sulfur-containing substance to produce "tarnish"; these are mostly airborne, but they can also be introduced through use, such as drinking wine from a silver goblet.

Tarnish can be beneficial; it can act as a seal by protecting underlying metal layers from exposure. In this form, it's called "patina". The formation of patina is essential for metals used outdoors or in damp conditions, i.e. copper roofing, outdoor copper, bronze, and brass statues and fittings. Patina is also the name given to tarnish on copper based metals; copper tarnish has a dark green color quality to it, as it turns blacker.
 

****

NOW BACK TO THE CHEMICAL REACTION.

BEFORE silver tarnishes, to prevent tarnish from forming in the first place, AND ONLY if you're not using the silver for eating, you can apply a thin coat of clear lacquer or clear lacquer nail polish all over the surface. I don't recommend smoking a pipe while handling any chemicals. 
 

****

****

When silver tarnishes, it combines with sulfur in the air, and forms silver sulfide. Silver sulfide is black. When a thin coating of silver sulfide forms on the surface of silver, it darkens the silver. 

The silver can be returned to its former luster by removing the silver sulfide coating from the surface.

Dah! The trick is to remove the silver sulfide coating from the surface WITHOUT removing more silver while you're doing this.
 

****

****

VARIOUS WAYS TO REMOVE TARNISH 
 

1. Gentler abrasives, like calcium carbonate, are often used by museums to clean tarnished silver as they cannot damage or scratch the silver and will not leave unwanted residues. These remove or dissolve the dark silver sulfide oxidation, but they also remove or dissolve some silver from the metal underlayers.

2. Polishes that contain an abrasive shine the silver by rubbing off the silver sulfide and some of the silver along with it.  Another kind of tarnish remover dissolves the silver sulfide in a liquid.  These polishes are used by dipping the silver into the liquid, or by rubbing the liquid on with a cloth and washing it off.  These polishes also remove some of the silver.

3. Tarnish can be removed by using abrasives like steel wool, sandpaper, emery paper, baking soda or a file to rub or polish the metal's dull surface. While this works, it removes some silver at the same time as removing the silver sulfide top tarnish metal layer.

4. Fine objects (such as silverware) may have the tarnish electrochemically reversed (non-destructively) by resting the objects on a piece of aluminium foil in a pot of boiling water with a small amount of salt or baking soda.  

****

#4 is Really Cool Science and you can try it yourself at home. The process chemically reduces the silver sulfide back to metallic silver. It doesn't remove any silver, and it actually converts the black silver sulfide to metallic silver. In other words, it reverses the tarnish process.  

****

BUT before we give you the recipe to try #4 at home, READ THESE CAVEATS: 

1. THIS STINKS. Really.
If you try this at home, open the windows. BE SURE YOU HAVE SUPERB VENTILATION, meaning fresh air circulating, because if the silver you're cleaning is heavily tarnished, you'll smell the sulfide byproduct.  Remember; hydrogen sulfide is the gas given off by rotten eggs.  And although most people don't talk about this, all metal tarnish removers will stink when used.

****

****

2. You MUST lay the silver on the  aluminum foil and be sure it is in contact with the aluminum foil,  or else the silver will turn black! It is the aluminum which causes the silver oxidation to move from the silver to the foil.  And, if your silver turns black because you failed to use the aluminum, or didn't have the silver contact the aluminum, then just re-do the process with the foil, in contact,  and the staining will reverse itself. Really. And you'll have learned something.

****

Here's THE RECIPE:

YOU WILL NEED TO:

FIRST Open the windows!  THEN READ through the process and procedure more than once, and have everything on hand before you start it.

****

****

WEAR SAFETY GLASSES, particularly if you're wearing 'gas permeable" contact lenses because you don't want them to bond with gaseous bi-products. If you don't have a pair of safety glasses handy, then wear sunglasses or reading glasses that cover your eyes.

****

****

INGREDIENTS


A Tarnished piece of silver

AND
Baking soda (sodium bicarbonate), approximately 1 cup per 1 gallon of water.

 

Why use sodium bicarbonate (baking soda)? 
The addition of baking soda improves the ease with which the electrons move between the silver and aluminum; it facilitates the reaction. Aluminum in pure water (H2O) won't remove silver tarnish because there is a film of aluminum hydroxide that stops the oxidation reaction. Sodium bicarbonate removes the surface film of aluminum hydroxide by dissolving it, to expose fresh metallic aluminum, ready for oxidation. The dissolved sodium bicarbonate also increases the ionic strength of the solution, which increases the rate of the reaction. In other words, just using sodium bicarbonate (baking soda) won't work; you need the silver to be in contact with aluminum foil, and submerged under a solution of JUST BOILED, HOT water and sodium bicarbonate (baking soda). And then you need to watch, and wait.

****

****

OPTIONAL:  WHAT YOU CAN ADD
    Don't add these until you've had some experience using this formula WITHOUT them.

You can add white vinegar, and a pinch or two of salt, to the baking soda, and combine them together before adding the HOT water that activates the process; but do this carefully as there is a reaction as it speeds up the chemical reaction. And because this combination increases the speed of the chemical reaction, and makes the solution corrosive, it's best used on heavily tarnished pieces and in a very well ventilated room!

****

****

GEAR
 

A Pan or dish large enough to completely immerse the silver. 
    Preferably use a glass pan or ceramic, and don't use a disposable aluminum roasting pan!

Enough new aluminum foil to cover the bottom of the pan.
Enough water to fill the pan.
A way to heat the water to boiling.
A container for the hot water (like a mixing bowl that is not metal).
A sink in which to place the active hot water chemical mixture while you're mixing it.
Hot pads or kitchen mitts to handle the container of heated water mixture.

****

DIRECTIONS

 

****

****

Line the bottom of the pan with aluminum foil. 

****

****

Set the silver object on top of the aluminum foil. 

****

****

Make sure the silver touches the aluminum.

****

****

Heat the water to boiling.

Yes, you can microwave it but don't cheat - make sure it's boiled before you remove it from the microwave.

Remove the boiling water from the heat, and transfer the HOT water into a non-metal mixing bowl, and place that in a sink!!!

****

****

To the hot water in the non-metal mixing bowl, now sitting in the sink, add about one cup of baking soda for each gallon of water.
 If you need only half a gallon of water, use half a cup of baking soda.

The mixture will froth a bit and may spill over; this is why you mix it in the sink.
 
If you're adding vinegar and / or salt at this point, to speed up the mixture as detailed in the ADDITIONS mentioned above, this mixture certainly will froth and spill so BE CAREFUL and watch out!

****

****

Pour the entire hot baking soda and water mixture into the pan containing the aluminum foil and the silver, be sure the silver is touching the aluminum foil,  and be sure to completely cover the silver.

****

****

Almost immediately, the tarnish will begin to disappear. 
PAY ATTENTION and KEEP WATCH.

If the silver is only lightly tarnished, all of the tarnish will disappear within several minutes.

Be patient and keep watching.
If the silver is badly tarnished, you may need to reheat the baking soda and water mixture, and give the silver several treatments to remove all of the tarnish.

****

****

Discard the liquid when the tarnish is sufficiently reduced, remove the silver, rinse it thoroughly in water, and air dry it.

Clean your tools and gear likewise. 

It's best to make up a fresh batch each time and to discard the used aluminum foil. 

****

HOW AND WHY DOES THIS WORK? 

****

****

When silver tarnishes, it combines with sulfur and forms silver sulfide. The chemical reaction using tarnished silver, aluminum, sodium bicarbonate, and hot water, causes the silver sulfide to convert back into silver. The reaction between silver sulfide and aluminum takes place when the two are in contact while they are immersed in a baking soda hot water solution.   This is an example of "displacement plating".

Aluminum is the reducing agent, and thereby reduces silver sulfide to elemental silver while forming aluminum sulfide.  Use just boiled water; the reaction is faster when the solution temperature is higher. The solution carries the sulfur, released from the silver, to the aluminum, where a layer of aluminum sulfide is formed. The aluminum sulfide then hydrolyzes to form aluminum hydroxide, Al(OH)3, and gaseous hydrogen sulfide, H2S.  That's what you smell.  The aluminum sulfide may adhere to the aluminum foil, or it may form tiny, pale yellow flakes in the bottom of the pan. 

The silver and aluminum must be in contact with each other, because a small electric current is produced naturally and flows between them during the reaction. This type of reaction, which involves an electric current, is called an electrochemical reaction. Reactions of this type are also used in batteries to produce electricity, and electricity can be used to facilitate plating.  Electroplating requires electricity, while displacement plating does not.

Be comforted by the smell. It means this is working!  The sulfur atoms are transferring from the silver to the aluminum, freeing the silver metal and forming aluminum sulfide. 

 

****

FEELING ADVENTUROUS? 

If you're feeling adventurous, and want to understand exactly how this works chemically, then check out the detailed chemical explanation, with diagrams, at "Examining The Reactions" from the Philadelphia Museum Of Art's article on Finishing Techniques In Metalwork, located here:
http://www.philamuseum.org/booklets/7_44_85_1.html?page=2

****

****

MORE RESOURCES

The Philadelphia Museum Of Art's article on Finishing Techniques In Metalwork, located here:
http://www.philamuseum.org/booklets/7_44_85_1.html?page=2

If you want to CREATE tarnish (GAK!), see this link:
http://www.philamuseum.org/booklets/7_45_90_1.html#tarnish

Herman Silver Restoration, Conservation & Preservation – the most thoroughly researched and practiced silver care information on the Web.: http://www.hermansilver.com/care.htm
Section on cleaning and polishing mesh and chain mail, using toothpaste, removing tea and coffee stains, salt encrustation, removing wax and labels. 

Common causes of gold tarnishing & prevention: https://www.onecklace.com/tips/does-real-gold-tarnish/

****

In short, have fun with your belongings and take care of them.  After all, you're a "picture worth a thousand words"!

****

****

I sign these newsletters "See Into The Invisible". Thanks for reading.

Best Wishes, 
Debra Spencer

All Content is © Debra Spencer, Suit Yourself™ International. Technical Library FAQ Index ISSN 2474-820X. All Rights Reserved. Please do not reproduce in part or in whole without express written consent. Thank you.
Top
All Content is ©2019 Debra Spencer, Appanage™at www.suityourself.international Suit Yourself ™ International, 120 Pendleton Point, Islesboro Island, Maine, 04848, USA 44n31 68w91 Technical Library FAQ Index ISSN 2474-820X. All Rights Reserved. Please do not reproduce in part or in whole without express written consent. Thank you.

Read Our Magazine! A Fortune Cookie Once A Week.

Enter your e-mail address to receive our magazine.
Email
Country
Please enter a valid email address.
Email address already subscribed.
All Content is ©2019 Debra Spencer, Appanage™at www.suityourself.international Suit Yourself ™ International, 120 Pendleton Point, Islesboro Island, Maine, 04848, USA 44n31 68w91 Technical Library FAQ Index ISSN 2474-820X. All Rights Reserved. Please do not reproduce in part or in whole without express written consent. Thank you.
Success consists of going from failure to failure without loss of enthusiasm. ~ Winston Churchill