How to repair a broken mirror frame – complete instructions!


Press down with mold to imprint

A beautiful mirror frame complements a room’s architecture and furnishing. If your treasured frame has been damaged in moving – or if you have bought an antique frame at a yard sale – how do you find out if your broken mirror frame is worth repairing? 

Decorative, carved, or gilded frames are worth restoring as long as the damage is not too severe. The important steps are: clean off the dirt, secure and reglue the corners, replace missing veneer and gesso, repaint and varnish the frame then re-install your mirror.

Examine your mirror frame to evaluate the damage.  Small wooden photo frames are not worth the effort but if you have a decorative, carved, or gesso frame with a gold leaf (gilding) then the following condition issues can be tackled by a competent handyman or woman:

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Examine the frame to evaluate the damage

Use your commonsense: small photo frames are so inexpensive that they are not worth restoring unless there are made of antique silver for example. Larger frames can sometimes be so badly damaged as to make repair uneconomical. If the frame is badly warped or seriously damaged by smoke or water – throw it in the garbage. Otherwise, follow the restoration steps outlined in this post:

Clean the frame

Antique frames especially ornate decorative ones with carving or ornate gesso generally accumulate layers of dirt over the years. Before repairing corners and damage it is important to clean the frame thoroughly.

Careful cleaning will often reveal the surprisingly vibrant original condition.

Clean mirror frame
Cleaning gilded frame with Q-tip

Removing loose dust

Start by wiping off the dust with a microfiber cloth. Then, taking great care not to damage the finish, use a soft toothbrush or Q-tip to get into the cavities.  If you have a small vacuum cleaner you can suck up dust but put a filter over the nozzle so you do not detach chips of loose gesso or wood.

Cleaning with liquids

Very often grease or dirt needs to be dissolved from the frame surface and the key advice is to always test any cleaning fluid on an inconspicuous part of the frame first. Water with conservation detergent or dish soap is often effective when applied with a Q-tip or cotton balls, but never use too much – waterlogged wood is not advisable!

Lemon oil polish and cleaner is a great way to restore dirty wooden frames but remember to test before using.

Study the nature of the frame materials and choose suitable cleaning agents. Silver polish, for example, is great for many metal frames. Never use abrasive cleaners or strong chemicals like ammonia or acetone without very careful testing.

Straightening a warped frame

Warped frame straightened with weights
Warped frame flattened out by gravity

Warping (that is twisting) of frame rails occurs in solid wood frames and is caused by temperature and humidity variations. If you have a special affection for the frame it can sometimes be rescued by soaking the wood with wet rags and flattening the whole thing down under a sheet of weighted plywood. Keep the rags wet and gravity (thanks Isaac Newton!) will gradually straighten out the frame.

Repairing loose corners

If the corner joints are loose the frame must be taken apart and re-glued. Mark each side so you will know how the pieces fit back together, then knock them apart with a rubber mallet. It may be easier to separate the corners with a putty knife, but take care not to mar the finish.

After removing any staples or nails chip away the old glue and sand the 45-degree joints to get back to bare wood.  Then use the picture framer’s trick of sizing the end grain joints with watered-down wood glue (50-50 water and glue).

Disc sander for making perfect 45 degree angles

Framer’s trick, using a disc sander set at 45 degrees to finesse the miter angles correctly and remove old adhesive. Otherwise, sand carefully by hand.

Sizing the joint with diluted wood glue
Sizing the joints with diluted wood glue

The end grain of a miter joint sucks up glue – so use a 50-50 mixture of water and wood glue to seal the grain. Allow this to dry before applying full-strength glue.

Clamping and gluing the frame

If you do not have picture-framers corner clamps, you can use bar clamps arranged at right-angles as shown below:

Apply woodworkers yellow glue to both miters, clamp and squeeze together. Wipe off the excess glue before it dries to save clean-up time.

Several inexpensive clamping systems are available and our favorite is the Powertec brand of band clamp:

POWERTEC Quick Release Band Clamp

Even if you are not planning to take up framing, this highly rated and reasonably-priced band clamp is worth buying.  The band size is 1-Inch wide x 13 feet long, constructed of high-strength nylon webbing, and is able to clamp square, round, rectangle, and uniquely shaped workpieces.

Numerous specialist framer’s clamps are available and Artistry in Glass recommends this model from Housolution:

Corner clamp secures corner miter

Housolution single handle corner clamp

90° clamp for woodworking with an adjustable swing jaw. The clamp is made of die-cast aluminum alloy. It allows two frame pieces of different thicknesses to be joined at a 90-degree angle. The maximum clamping range is approx. 2.68in; jaw width: 3.74in; jaw depth: 1.4in, it can clamp materials like steel, metal tube, wood, gesso, & plastic.

Reinforcing the glued miter joint

Even though the glue joints are strong it is preferable to reinforce the corners with mechanical fastenings:

Dewalt brad nailer

If you have a brad nailer in your toolbox a simple way to secure the miters is to shoot a couple of brads at right-angles into the corner of the frame.

Pilot hole in hardwood

A hand-hammered brad is a good way to secure the corner. With oak or other hard-wood frames, drill a pilot hole.

V nails

V-nails are used by professional framers to reinforce the corners but they require expensive tools like this top-rated nailer available on Amazon.

L-shaped corner brace

Metal L-shaped corner braces are a simple way to secure the corners. Attached to the back of the frame they will not show when the mirror is on the wall. Choose screws with care so they do not go through to the front.

Corner braces may not be practical on very thin moldings because the screws may split the wood, but they are excellent for heavy mirror frames. The braces come in brass and plated steel. Brass is best because it is less bulky and will not cause rust stains.

Repairing corners without taking them apart

In many old frames, the corners have separated slightly but are still strong. If there is only one loose corner, or if the separations are slight, you can sometimes re-glue without taking the entire frame apart.

Cracked miter joint

Study the corners and if possible open the joint just a little, scrape out as much of the old glue as you can, apply fresh glue, then clamp the joint closed. If the joint is still strong, just fill the hairline gap with epoxy putty and complete the repair as shown below.

Delaminated veneers or inlays

One of the commonest types of damage to mirror frames is the separation and delaminating of wood veneers that are applied as decorative finishes to the surface of wooden frames. Wood veneers and other decorative inlays (mother of pearl, bone, enamel, etc) become detached because they expand at different rates compared to the substrate when subjected to high humidity or moisture.

Fixing badly damaged veneer is really a project for the experienced furniture re-finisher but a novice can easily make minor repairs. First, remove all the loose or damaged veneer and clean and sand the substrate to remove any old glue. Then, there are three main approaches:

Replace with real veneer

Loose veneer replaced
Mark new veneer and cut to fit

Carefully remove the damaged veneer and trim the missing areas to make a simple shape for replacement. Clean the wood substrate to remove the old glue. Cut a new piece of matching veneer to fit and glue it in place. Finish by filling small gaps with wood filler, sanding then staining and polishing to match the original.

Fill with epoxy putty

If I do not have a suitable replacement veneer, how do I repair a damaged mirror frame?

To restore the missing veneer: remove the loose material, clean the substrate to remove the old glue, fill the space with epoxy putty or plastic wood, sand the putty, then paint or stain to match the original veneer.

Epoxy Putty Stick

Mohawk Finishing Products EPOXY Putty is available in numerous wood tones. It bonds to aluminum, glass, and wood, does not shrink, sets up in about one hour, and can be sanded and stained to match the missing veneer

Epoxy putty replacing missing veneer
Filling the missing veneer with plastic wood or putty

As an alternative to using veneer: fill the missing areas with epoxy putty, plastic wood, or suitable filler like Mohawk epoxy putty. This is good for small areas and easier to apply than veneer. The stages are to squidge on the putty and mold flat with a palette knife (the smoother you get the putty, the less sanding you will have to do). Then sand the dried putty then stain or paint to match the old veneer.

Puncture blistered veneer and re-glue

Sometimes veneer swells and blisters without becoming detached. In this case, the best strategy is to puncture the blister by cutting a small slit with a sharp utility knife. Introduce a little wood glue into the slit and flatten the blister with a warm iron (low temperature, cotton or linen setting).

Puncture blister in veneer
Puncture the blistered veneer with a utility knife
Ironing the veneer blister
Flatten the blister with an iron

Iron with care, place protective cotton fabric under the iron if you are nervous.

Replace missing gesso & decorative elements

The most common damage to a decorative frame is missing ornamental elements – chiefly gesso but also carved wood. When used in picture frames, gesso is a mixture of chalk, white pigment, and animal glue that is molded to form the ornate, three-dimensional decorations. It is covered by red-colored clay called “bole” before being gilded with gold leaf.

Gesso is very brittle and easily broken off when subjected to stress. Complete repair, including gold-leafing, is the province of restoration experts but, do not be afraid. Very acceptable fixes can be done by the handy homeowner. The main steps are:

  • Remove loose gesso & save for re-gluing
  • Clean the wooden substrate
  • Make a mold from an undamaged area
  • Fill the missing area with epoxy putty
  • Use the mold to imprint the epoxy
  • Sand, paint and gold-leaf to match the original

Many frames have cracked and loose gesso. Carefully detach the loose pieces, clean the substrate and glue the pieces back using wood glue. Fill any small cracks with epoxy putty.

Making a mold

To recreate complex 3-D decorations you need to make a mold and cast the replacement piece. So two items are needed: mold-making materials and epoxy putty or plaster of pairs to cast into the mold.

There are two main types of mold – flexible silicone-based molds (Amazon) and hard, clay, or epoxy-based molds. We recommend hard molds part from a 2-part epoxy putty such as “Epoxy-Sculpt” (we also use this for filling the mold).

Mix the epoxy putty and press it firmly into an undamaged area of the frame that has the decoration that you wish to duplicate. When the putty is dry your mold is ready and can be removed. (Air-drying modeling clay, available here on Amazon, can also be used but is not as strong as the epoxy).

Make a mold with 2-part epoxy
Making a mold from epoxy putty (detached mold at left)

If you use a flexible mold, you have to take the cast material and carefully sculpt it to fit back in the frame. With a hard mold, the replacement putty can be added to the frame and imprinted in-situ as shown in the drawings below:

Clean loose gesso and fill with epoxy
Clean the frame then fill the gap with 2-part epoxy putty

Prepare by removing all glue and dirt from under the detached gesso. Sand the wood to create a rough surface (“tooth”) for the epoxy to stick to. Then fill the space with 2-part epoxy putty (we like Epoxy-Sculpt available here on Amazon). Traditionists can also use Plaster of Paris.

Press down with mold to imprint
Imprinting the 3-D decoration

Using your hard epoxy mold, line it up with the frame decoration and press down firmly to imprint the design. (Dust the mold with a little corn starch or talcum powder so the putty does not stick).

Finishing – painting & gilding

The final stage in your epic gesso repair journey is to gild the putty to match the original. First, check the newly molded material, fill any gaps with new putty, and then sand it smooth ready for gilding.

Most traditional gesso has an undercoat of red “bole” that gives a subtle warm, sub-color to the gold. Simulate this finish by painting with red-brown acrylic paint. Then purchase an inexpensive gilding kit from this page on Amazon and follow the instructions to complete your repair masterpiece.

Restoring carved wooden decorative elements

Solid wood frames are also embellished with 3-D decoration mainly created by carving. Carved wood dries out and becomes brittle if not correctly preserved by oiling and pieces often break and fall off. Repairs can be made using the same methods used for replacing missing gesso – except that the finishing is by wood staining rather than gilding.

Damaged wood corners of picture frames
Damaged corners of mirror frames

Simple wooden frames are repaired in the same way as for gesso. Clean off loose fragments, fill with epoxy putty or wood filler, sand smooth then paint or stain to match.

Corner of carved mirror frame
Carved solid wood frame

Elaborate 3-D carved frames with missing wood will require that you make a mold from an identical, undamaged area of the frame. In the case shown above, the newly cast epoxy part must be carefully sanded and modeled to fit back in the damaged corner. Consult the professionals at Artistry in Glass if you feel that this type of project is beyond your capabilities.

Worn gilded or painted surfaces

Antique mirror frames often show normal wear and tear with age and gilding can easily be spruced up by applying new gold leaf. Do not be afraid – follow the instructions given in gilding kits shown on this Amazon page, and have fun making your old frames gleam like new!

If you are nervous about tackling real gilding, acceptable results can be obtained by using some of the wide range of gold paints now available on Amazon.

Comprehensive mirror information available at Artistry in Glass:

Check out our antique restoration services:

John

I was an exploration geologist and University Professor working in Botswana, Zambia, Brazil, Saudi Arabia, the Netherlands, and other countries before opening Artistry in Glass in 1986. In my more than 30 years of experience, I have brought my technical abilities as a scientist to the trade of glasswork. In this time I have become an industry expert in glass and glass-related skills. Watch out for special insider tips developed from my detailed knowledge of the glass business.

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