How to repair cracked stained glass – tips from an expert!

crack in clear glass healed by runny glue

Stained glass is beautiful but fragile and brittle. Rough treatment or impacts with hard objects can easily crack the little pieces of glass that make up a stained glass panel. Do you need to replace the entire window? How do you repair cracked stained glass – find out in this article from a stained glass expert!

Cracked stained glass can be repaired in situ with UV, epoxy, or cyanoacrylate adhesives – saving the homeowner the high cost of panel removal & reinstallation  Learn how to repair cracked stained glass in this informative article.

Stained glass windows in homes

Just waiting to get broken!

The commonest locations for residential stained glass are entryways – where homeowners, wishing to make an impression on their visitors, commonly invest in elaborate door panels or sidelights. Other locations for stained glass include bathroom privacy windows and skylights but by far the most prone to damage are door panels and sidelights.

Traditional entry doors with beveled glass
Traditional entry doors with stained glass panels for light and beauty

Entryways are uniquely vulnerable to damage because they are high-traffic areas with family, friends, and strangers, coming and going (and potential intruders trying to break in!).

At Artistry in Glass, we have been fixing broken stained glass since 1986 and we never ceased to be amazed by how glass can get broken – culprits range from golf balls to pot-bellied pigs, from petulant toddlers to Irish Wolfhounds – jump to this section for the full list.

Learn more about how cracks occur in glass by jumping to this section.

Accidents will happen so be prepared! First: learn what to do if your stained glass gets cracked.

What to do if your stained glass gets cracked

  • As a safety precaution, jump to this info on the dangers of lead poisoning before starting any stained glass repair project.
  • Examine the damage carefully and take photos with your cell phone for insurance and repair purposes.
  • Take close-up images of the cracks and also an overall view so that the repair company can evaluate the method of installation and the difficulties that may be involved. Include a closeup of the molding – the pieces of wood or metal used to hold the panel in place.
  • Stabilize the window by covering the cracks with sturdy duct tape.
  • Save any broken pieces that have become detached – they may be useful for color-matching of replacement pieces.
  • Study this post to see if you can complete a home repair – otherwise,call local stained glass shops and email them images for advice. Tucson customers contact Artistry in Glass

Serious damage will require professional repair and unfortunately, with glass removal and reinstallation, typical costs exceed $1000.00. This is a substantial financial setback especially as many homeowners insurance policies carry a $500.00 or $1000.00 deductible.

So this article will show how minor cracks can be repaired by a competent homeowner but, before we explain, learn how to avoid the problem in the first place:

Avoid stained glass damage – install protective glass

These days, sensible homeowners guard against breakage by installing protective tempered glass on the outside (and in some cases, also on the inside) of their art glass panels. However, many panels installed before the mid-1980s are stand-alone and unprotected.

Insider tips from a glass professional

Homeowners with unprotected stained glass should consider retrofitting their doors and sidelights with sheets of tempered glass to protect against expensive damage.

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Modern black hole sidelights

Leaded glass sidelights are vulnerable to damage either accidentally or deliberately as in a burglary. We recommend installing protective tempered glass on the outside to guard against accidental or deliberate breakage.

Learn more about window treatments by reading this comprehensive guide

The problem of cracked stained glass

Why is cracked stained glass tricky to fix?

Most stained (strictly leaded) or beveled glass windows are made by connecting separate pieces of glass with “H-shaped metal (generally lead but also zinc, brass or copper) came as shown in the drawing below:

"H"-shaped lead or zinc came.

To replace a piece of cracked stained glass, the panel must be taken apart so that the broken segment can be taken out.

The main expense of most stained glass repairs is therefore the labor involved in removing the panel, boarding up the opening, transporting the window to the workshop, and returning to re-install the restored panel.

Can a crack be repaired in place?

In view of the high cost of removing the damaged panel – what are the alternatives? Can an effective repair be made with the window left in place?

Yes – several options are available:

  • Remove the damaged piece and replace it (some soldering skill is required).
  • Glue the cracked glass together using a variety of adhesives.
  • Cover the crack with adhesive tape to match the lead came.

Remove and replace the broken piece

A reasonably handy person can remove a broken piece of glass from a leaded glass panel using pliers and screwdrivers or chisels. This is called the “drop-in” repair method by traditional glaziers.

Repair with bending lead

By carefully bending back the H-shaped lead a handy homeowner can remove the busted piece of glass. Take this piece to your local stained glass shop and ask them to cut you a replacement piece (make it very slightly smaller).

With some dexterity and skill, the homeowner can maneuver the replacement glass back into position and carefully bend the soft, ductile lead back into place.

Do not be afraid! Even without soldering skills, you can coax the soft lead around the new glass. If the metal gets torn, use JB Weld to fill the gaps and strengthen the repair. Take your time and smooth the adhesive to match the profile of the old lead.

Note that this came-bending method is not possible if the came (normally lead) is made of harder metal like zinc or brass.

Glue the crack with adhesive

Many experts favor gluing instead of replacing glass, especially on older, valuable windows where it may not be possible to match the original antique glass.

Skillful gluing can stabilize the panel and minimize the possibility of further damage. However, the visual appearance and perfection of the repair require considerable expertise: read on to learn the tricks of the trade.

Preparation for gluing – it is very important to clean the cracked glass thoroughly before gluing.

Take great care because the invisibility of the glued joint will depend on the accuracy with which it is joined together. The crucial requirement for a perfect glue joint is to make sure the two broken pieces are lined up exactly. If there is dirt (a single molecule) in the crack, the repair will not be invisible.

The visibility of a glass crack is due to the reflection of light from the broken surfaces. When the microscopic gap between the two parts is filled with glue, the reflection disappears and the only sign of the crack should be a fine, almost invisible line.

crack in clear glass healed by runny glue

The internal reflections, along this hairline crack, disappear as a low-viscosity adhesive is sucked in by capillary action. This adhesive is UV 7021, low-viscosity UV-activated glue from CR Laurence Co. (available here from Amazon).

For the most invisible glue joint, take care to clean and align the two broken pieces as perfectly as possible.

Choosing the correct adhesive

For most hairline cracks the best solution is to use a low-viscosity (runny) glue that will fill the crack by capillary action.

Professional glass workers swear by HXTAL NYL-1 Epoxy – an optically clear, 2-part adhesive available from specialist restoration companies (but not on Amazon). Hxtal is reported to be non-yellowing and provides very strong bonds in glass and crystal – it is, however, very expensive and has a long curing time (7 days to achieve 90% strength).

So, for the home crack repairer, we highly recommend either UV glue or straight superglue (buy the runny, not the gel)

Two adhesives recommended by Artistry in Glass

Professional UV-activated adhesive sets up almost instantly in sunlight or UV light

Highly recommended for strength and non-yellowing – but only use for hair-line cracks – it will not fill gaps. Set up in sunlight or using the lamp shown below:

Loctite glass glue is a type of cyanoacrylate superglue

The Loctite company is the original inventor of superglue and their Glass Glue is effective. Note that regular (generic) brands of superglue also work.

Our favorite UV lamp is compact but powerful enough to set up UV glue in 30 seconds or less. Apply the glue by capillary action, align the pieces then shine the UV light (the closer the better).

Open or complex cracks

It’s important to understand that Hxtal, superglue, or UV glues will not fill cracks so if you have damage with cavities or spaces there are two alternate adhesive options.

Option #1 Epoxy

If the window is in a safe, protected, interior location, your best bet is to use a regular two-part clear epoxy like J-B Weld 50112 5 minute . Skillful amateurs can color-match by adding very small quantities of liquid or powdered pigment to one part of the 2 part epoxy before mixing. Fill the gaps with care, then smooth and clean the excess glue.

Option #2 Clear silicone

If the cracked panel is an exterior window, subject to flexing by the wind and weather, then a flexible adhesive is highly desirable. We like clear silicone RTV 732 by Dow Corning. It comes in small 2oz tubes, which makes it easy to work with, with little or no waste.

Clear silicone is especially effective for opalescent glass and can be colored, like epoxy, by adding small amounts of pigments. Carefully apply the silicone to the gaps/cracks and remove the excess with a sharp razor blade.

High-quality clear silicone is excellent for making flexible crack or gap repairs. Available here on Amazon.

Clean the excess adhesive

To complete the gluing, clean off the excess adhesive with a sharp razor blade. The main objective is to stabilize the glass to prevent further damage. We like to use the original glass wherever possible to preserve the authenticity of the art. If the crack is still offensive to the eye, consider adding lead tape as described below:

Cover the crack with adhesive tape

Used together with gluing, the addition of adhesive lead tape can successfully disguise a crack in stained glass.

Sometimes this extra lead-line trick is done during the manufacturing process. The stained glass expert can often tell when an unexpected crack has been fixed with lead came during the manufacturing process.

Cracked leaf repaired with lead line

Spot the extra line! A broken leaf in this antique stained glass panel was fixed by inserting an extra lead line – saving the expensive and time-consuming process of re-painting and firing in the kiln.

The professional glass artist will cut a flat strip of lead from H-came, glue it over the crack, and solder it to adjacent lead lines to complete the repair.

In the case of Tiffany-style, copper foiled stained glass – the expert will add another foil line and carefully cover it with solder.

The amateur repairer can make do with adhesive-backed lead tape like the brand below:

Gallery glass instant lead lines, 18 Strips 24″ x 1/8″, are used to stick over and cover glass cracks. Double up the tape if necessary and use patina to match the finish with the original lead.

Use your skill and judgment to position the lead tape and consider adding “unnecessary” tape to an undamaged area of the panel if this will create a symmetrical design.

Finish your repair by cleaning & polishing

Use the advice in this post to clean and polish your restored stained glass panel. Always be gentle (do not press too hard) to avoid further damage.

How stained glass cracks

Glass is easily broken by impacts but can also crack as a result of faulty design. This corner of a historic 1900-era panel is from the Bradley House, built by Frank Lloyd Wright in Kankakee, Illinois.

Cracks in Bradley House stained glass
Corner of a window designed by Frank Lloyd Wright

The cracks in this Frank Lloyd Wright panel are examples of unwise fabrication – the sharp “inside” angle is especially vulnerable to cracking. Historic photographs show that every single window in the Bradley House has cracks in these vulnerable corners.

It is interesting to imagine that the great architect, exhibiting early examples of youthful ego probably overruled the glaziers and insisted on this dangerous design in what was his very first Prairie-style house.

Serious cracks and missing pieces need the expertise of professionals like Artistry in Glass.

Study this video to see if your stained glass window is worth fixing:

The danger of lead

Lead in the form of came (channel) or in solder is an important part of a stained glass panel and lead is poisonous.

In summary: stained glass windows pose no threat to the homeowner providing simple precautions are taken. But, please read this post to learn all about the danger of lead in stained glass.

Safety warning glass is dangerous!

Lead is a dangerous poison, especially for young children and pregnant mothers! Take great care to wash your hands thoroughly after any contact with lead.

Unusual glass-breaking culprits

  • Golf ball impact from a sliced drive on the 13th fairway.
  • Vietnamese pot-bellied pig collides with a ming vase which hits the panel.
  • The wagging tail of an Irish Wolfhound.
  • A petulant toddler dissatisfied with her happy-meal premium throws it against the window.
  • Teenagers playing catch with a baseball.
  • Teenagers playing basketball in the foyer.
  • A pebble ricochets from a lawnmower or strimmer.
  • An ill-fated custodian drops a light bulb down onto a skylight.
  • A domestic violence incident.
  • A drunken resident stumbles against the door.
  • A cleaner moves the Lazy-boy recliner just 1 inch out of place and the cat, jumping onto his normal position, rocks the chair backward to break a stained glass panel.
  • An attempted burglary or home invasion.

In conclusion

If you have a crack in your stained glass window it may be possible to repair it, in situ, and save big bucks – by following the advice in this post.

Remember, never jeopardize the safety and security of your family by taking risks – be sure to contact Artistry in Glass at 520-320-0104 – if you are uncertain as to the best course of action.

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I was an exploration geologist and University Professor working in Botswana, Zambia, Brazil, Saudi Arabia, the Netherlands, Portugal, and other countries before opening Artistry in Glass in 1986. In my more than 35 years of experience, I have brought my technical abilities as a scientist to the trade of glasswork. During 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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