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 ...and thanks for stopping by. I'm Claire Douglas,  DIY and home interiors writer specialising in money-saving and creative home interior projects. I've spent years developing my 'bespoke on a budget' approach to DIY and home interiors and I love sharing all my tips and tricks in tutorials and posts here on my blog, in articles I write for some of the leading titles, in the press, on Instagram, Tiktok and my online course

  • Claire Douglas

5 Clever Ways to Prevent Bathroom Mirror Desilvering

Updated: Jun 9

Bathroom mirror de-silvering causes unsightly black edges; here's how to avoid the dreaded mirror rust and protect your bathroom mirror.

a bathroom mirror with desilvering - a rusted edge
Mirror desilvering

I wrote a post a while ago about how to treat mirror desilvering on a bathroom mirror and was blown away by how many views it got. It turns out that bathroom mirror repair is an unexpectedly hot topic and there are tens of thousands of people looking for a) ways to avoid a black edge on a mirror and b) bathroom mirror repair tips.

The original post looked at ways to remove the oxidation, aka rust that forms around the edge of a mirror when water penetrates it, aka mirror desilvering (this is the name for when a mirror shows wear and tear in the form of unsightly rusting and degradation).

Unfortunately, once your mirror has started desilvering, there's no easy way to restore the edge to its former glory. However, there are ways to reduce the appearance of the issue, which I detailed in the step-by-step tutorial. It’s preferable to prevent the issue from happening in the first place, so let’s look at a few ways to do this…

How to avoid the black edge on a mirror appearing (desilvering)

1. Apply Sealant

Apply a layer of sealant to the mirror edge. A clear silicon sealant is ideal for this task as it won’t be visible but it should act as a barrier to prevent water penetration (the nemesis of mirrors!)

2. Apply WD40

WD40 can being used to spray the bottom edge of a bathroom mirror to prevent mirror desilvering
WD40 treating mirror desilvering

WD40 gets its name from its intended purpose, Water Dispersement (WD) and the 40 is the successful number attempt. Originally designed for the aerospace industry this handy spray can actually help you with your bathroom mirror dilemma. Spray a layer of WD40 around the edge of your mirror to ensure no water can get in. This prevents avoids the black edge from appearing.

3. Use an adhesive sealant

If you are using a mirror adhesive to attach a mirror to the wall, then pick one that also acts as a sealant to save buying multiple products. There are lots of products on the market that can be used to glue the back of the mirror to a wall as well as to seal the edge or joints of the mirror to prevent the edge from going black and unsightly because of mirror desilvering.

4. Keep air moisture under control

portable dehumidifier in front of window
My recommended dehumidifier

Bathrooms often suffer from high air moisture because of the steam from baths, showers and running water in the sink. Using your bathroom extractor fan or introducing a dehumidifier will reduce the excess moisture in the air, which condenses when it hits a cold surface like your bathroom mirror. While we are on the subject of dehumidifiers, I recommend using one in your home throughout the winter if you a) struggle with condensation around the home, b) have a lot of window condensation to tackle or c)are trying to keep your home warm with reduced or no heating. Here's the post I wrote about how to use a dehumidifier to stop condensation.

5. Wipe your mirror down after every bath or shower

The reason the base edge of a bathroom mirror is often the worst affected by the black edge (de-silvering) is that often, the condensation runs down the mirror and collects in droplets underneath the mirror until the droplets become large enough to drip below. All the time that the water is collecting along the base of the mirror edge it is potentially penetrating the mirror and attacking the silver backing.

Wiping excess moisture from the mirror after every bath or shower limits the volume of water given the chance to penetrate it. It’s worth noting that although points 4 and 5 are important tasks in the battle to prevent mirror desilvering, they will not be sufficient on their own and should be combined with 1,2 or 3.

Is it too late?

If it's too late and your mirror has already become rusted around the edge and looks awful, you have a couple of options a) pop over to my post to see how I used WD40 to remove the rust and make the mirror look better than it did (worth noting it wasn't back to pre-rust levels of loveliness!) or b) come back tomorrow for the post I'm going to share about how to create a stylish DIY frame for a mirror to cover the affected area and restore the mirror's beauty or c) check out the below curated shopping guide of cool mirrors.

moodboard of selection of stylish mirrors

Click below to shop each mirror (ad/affiliate links)

5. Wavy

Alternatively, you could read the post I wrote about how to make a DIY bobbin frame for a mirror as this can be positioned to cover the affected area of your mirror and bobbin mirrors are cool!

Mirror desilvering FAQs

Why do mirrors go black on the edge?

Mirrors can develop black edges due to a process called desilvering. This occurs when the reflective backing of the mirror deteriorates over time, often as a result of exposure to moisture or other environmental factors. As the silvering on the back of the mirror degrades, it can create black spots or edges, compromising the mirror's reflective quality. Proper sealing and maintenance can help prevent or slow down this process.

Why is it called desilvering along a mirror edge?

The term "desilvering" refers to the degradation or loss of the reflective silver coating on the back of a mirror. Over time, this silver backing can deteriorate due to exposure to moisture, humidity, or other environmental factors. As the silvering degrades, the mirror's reflective quality diminishes, leading to a blackening effect at the edges, commonly referred to as desilvering. This term specifically highlights the loss or degradation of the silver material from the mirror surface.

How do I seal the edge of a bathroom mirror to prevent desilvering?

To prevent desilvering on a bathroom mirror, you can apply a silicone sealant around the mirror's edges. Ensure that the area is clean and dry before applying the sealant. Make sure to use a mildew-resistant and moisture-resistant silicone sealant to effectively protect the edges.

Can I use anything other than silicone sealant to seal a bathroom mirror edge?

While silicone sealant is commonly used to seal the edges of a bathroom mirror, you may also consider using other types of specialized mirror edge sealants or adhesives, such as mirror mastic. Mirror mastic is specifically designed for use with mirrors and can provide a strong and durable bond. Choose a product suitable for use in high-moisture environments like bathrooms. Always follow the manufacturer's instructions for best results.

Where next?

Here are some DIY furniture-related posts you might enjoy…


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