How to fix mirror backing

A mirror, in its most basic form, is a piece of glass coated with silver and protected with backing paint. The silver coating is not paint - it is a very thin layer of pure elemental silver that forms directly on the glass as the silver chemicals react with each other.

This video shows you how to re-silver a beveled bathroom mirror using our Mini Silver Kit.The photo on the right is an old engraved mirror that has been re-silvered using this process.

To silver and re-silver telescopes, sextants and other scientific mirrors see our page on scientific instruments.

If the glass is beveled, curved, beautifully engraved (as in this photo), carefully shaped or has sentimental value it is certainly worth re-silvering.

Mirroring (re-silvering) is a very wet process. In order to re-silver a mirror, you will have to remove it from its frame. This is a good time to see if the frame itself needs to be strengthened or repaired. The best time to do this is after you have carefully removed the mirror.

Re-silvering a mirror does not affect the glass itself. It will not fix any scratches, chips or cracks. In fact, the bright new silver could make these defects more noticeable. If your mirror is scratched, look carefully to see if the scratch is in the glass or the silver. It is not possible to polish a scratch out of the glass by hand but re-silvering will remove a scratch in the silver layer.

Re-silvering one small section of a mirror

Before you decide to re-silver just one section of an old mirror, check to see if the backing paint is strong, smooth and firmly attached to the glass. Pouring or spraying silvering chemicals onto fragile backing paint will probably lift it off and make the problem worse.

Even if the backing paint is in excellent condition, and you are able to remove just enough of it to silver one section of the mirror, there will be a fine gray line between the old silver and the new silver. Only you can decide it this is a problem. Of course, if you try this and decide that the result was not what you want, you can always strip the entire mirror and re-silver it. Silvering does not change the glass – you can re-silver a piece as many times as you like if you remove all of the old paint and silver first.

For this process you will need a Mini Silver Kit and extra fine pumice. Polish the affected area with a paste of distilled water and pumice to smooth the edges of the surrounding backing paint and silver. Follow our Mini Silver Kit Instructions to clean, tin and silver the scratch. You can always add a second layer of silver if you think the first layer is not thick enough. Once the silver is dry, protect it with the paint in the Mini Silver Kit.

Mirror scratch repair paint

The paint that is sold to repair scratches in mirrors is made of extremely small flakes of aluminum. If you paint it on the mirror and view it from one angle, it looks perfect. If you view it from another angle it looks like a bright white line. The flakes of aluminum do not reflect light in the same way that individual silver crystals do when the crystals have formed on the glass during the silver mirroring process.

An alternative to re-silvering

The alternative to re-silvering your old glass is to remove all of the silver and paint and then buy a new mirror cut to size and place it behind the old glass in the same frame. The old glass and the new mirror must be perfectly clean before you put them together.

This trick does not work if

• The frame is not strong enough to support the extra weight and thickness of the additional glass.
• The glass has a design engraved into it. The back of the design will be reflected by the mirror behind it.
• The trick does work if your mirror only has beveled edges because the back of the bevel is flat and it will not create a double reflection.

Tips on cleaning an old mirror

• Never use a dust cloth or vacuum to remove the dust from the back of an old mirror. Leave it dusty. The integrity of the silver depends on the integrity of the backing paint. Suction and friction can loosen the backing paint and expose the silver to further corrosion.
• Clean the mirror face by spraying glass cleaner on an old towel or T-shirt and then wiping the glass. Water is the enemy of mirrors. Do not spray the cleaner directly on the glass.
• See more about how best to care for antique furniture including mirrors here: Porch.com

Mercury mirrors

The process of creating a mirror with silver was invented by Baron Justus von Liebig in 1835. Before that, mirrors were made with mercury and tin. Louis XIV’s Hall of Mirrors at Versailles in Paris are mercury mirrors. If the back of your old mirror is covered with fine white dust and it has no paint, it may be a mercury mirror but they are extremely rare. Given that mercury is poisonous and should only be handled with gloves, they do not have a high monetary value.

We welcome any questions you may have regarding re-silvering an old mirror. Contact Us

From time to time, I’ve spotted a great vintage mirror at a flea market or thrift shop, but if the mirror had dark spots on the glass, well, I’ve just left it there because I didn’t really know how to fix the problem.

I saw this really cool geometric mirror for a great price at the thrift store the other week, and instead of running from my “black spot fear”, I decided to face it head on and figure it out instead. It turns out there are a few tricks you can use to either totally repair, minimize, or conceal the damage that was caused from moisture on the silver backing of the mirror.

If you have a mirror you’d like to fix, you’ll notice that there are two types of black spots: some of the spots are opaque areas of damage on the reflective coating and others are actually where the backing has been scraped or eaten away so you can see through past the back of the mirror (in other words, if you put your finger over that spot on the back of the mirror you would see your finger through the front of the glass).

Depending on the type, placement, and severity of spot, here are your options to help give your mirror a second life:

Re-silver the mirror: OK, this is definitely the most involved option to resolve the problem. Re-silvering is basically removing the protective, silver backing of the mirror and reapplying those layers again on the back of the glass. It is a more technical process (see a full tutorial here), and I think the larger the mirror, the harder it would be for a first timer.

But it is an option if your mirror’s black spots are overwhelming and totally beyond any other repair (and actually, I think it looks like fun to try!).

Use aluminum foil: Say what?? Yep, this trick works really well if you have the kind of spots where the backing has been scraped off and you can see through to the other side of the glass.

All you need to do is smooth out small pieces of aluminum foil and tape them with clear tape to the back of the mirror.

The reflective foil is seen from the front and is much less noticeable when you hang it back up again. Since you probably already have tape and foil on hand, this is an easy solution for a few trouble spots.

Mirror-like spray paint: This is a similar option to the aluminum foil (this is what I used) and essentially does the same thing if you have the clear spot issue.

If you have a bunch of small areas all over your mirror, it’s probably more efficient to just spray the whole back so any little spots get covered and you don’t have to foil 20 different areas.

While you can use the above tricks to fix or minimize damage on the edges, you can also tape off a border or design, use a few coats of spray paint (I like this one a lot and this one), and create a new frame that covers up the spots instead!

I’ve found that most spray paints will hold up just fine when cleaning the mirror with glass cleaner, but you can always buy a small craft mirror and test out your paint first if you want to make sure it won’t wipe right off during cleaning.

See?? That original dark area looks SO much better. Since moisture is what caused the spotty damage in the first place, you’ll want to make sure you also protect your new mirror from further damage by using a layer of protective polyurethane on the back of the mirror as well (do it before taping the foil or after using the mirror spray paint if you are doing those options).

While it does still have that imperfect “vintage feel” to the glass, the makeover process made such a difference to this forgotten treasure, and I will definitely think again before walking away from another cool mirror find in the future.

Here’s a similar mirror to mine if that’s what you’ve been looking for, and our full length mirror guide (splurge vs. save) is here! xo. Laura

P.S. Check out more cute mirrors and home decor on our wishlist and shopping pages!

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