Should Epoxy or Super Glue be Used for Broken Ceramic or Sculpture Repair? How do I choose?
There is a common misconception about the interchangeability of super glues and epoxy adhesives for repairing pottery, ceramic, china, figurines, and sculptures. While both are strong, they serve different purposes and have distinct properties suited for various repairs. Choosing the right adhesive is essential for a successful and lasting repair.
Before attempting to repair a potentially valuable broken item, it’s crucial to address the following questions:
1) What are the characteristics of these adhesives?
2) Understand the properties of the glues you are considering, such as their bonding strength, curing time, transparency, and suitability for materials like pottery, ceramic, stone, or china.
3) What potential challenges could these adhesives pose? Consider issues such as yellowing over time, toxicity, difficulty in removal, or incompatibility with certain materials that might damage the item further.
4) What additional information do you need about these adhesives for effective repairs?
Research the optimal application methods, temperature and humidity requirements during curing, and whether the adhesive is reversible in case the repair needs to be redone.
Answering these questions thoroughly will ensure that you choose the most appropriate adhesive and approach, preserving both the structural integrity and value of the item
Let's break down the differences between super glue and epoxy adhesives:
Epoxies
Epoxies have a strong bond, strong structural strength and are better at filling voids between parts. Epoxy consists of two parts, the hardener and the resin that must be combined and mixed well. In some brands, the resin and the hardeners are different colors. Mixing the two generates a third color that can tell you when the two parts are properly mixed. Epoxies come in different sizes, names, containers, and squeezing styles. Different epoxies have different purposes mending, filling, and protective coating. In this write-up, we'll focus on mending epoxies only as compared to super glues.
Super glues are a single component made from Cyanoacrylate that hardens rapidly with a strong bond when exposed to moisture in the air. It is a very thin watery liquid that can be used directly out of the bottle without mixing. However, Super glues have very low shear strength (side push or pull) which means that the parts bonded will resist direct pulling but not off-angle stress. Super glues require a tight fit given the liquidity and very thin glue layer between the broken parts for proper bonding and therefore will not fill in voids. Superglues work best on non-porous materials.
Lastly, Superglues affects subsequent layers of restoration such as fillers or paints used for implementing a seamless repair. With time, it will interact with this layer and will appear in a different color like the example on the right.
Super glue
Super glue interacting with repair layers (e.g., paint)
Cementing and Filling in Gaps Unlike super glues, mending epoxies are also gap fillers given the thickness of the parts mix. If the broken pieces do not have a perfect fit, epoxy will fill in the gaps while creating a bond between the broken pieces.
2-part even ratio mix
Epoxies Setting Time Epoxies are available for different sets and cure times and can vary from minutes to several hours. Therefore, holding the cemented parts in place until the epoxy sets can be a challenge. This time depends upon the chemical composition of the hardener. You will want to consider whether quick-setting or slow-setting epoxy is the most appropriate for your project.
Holding the cemented pieces by hand and waiting for the duration of the cure time is not practical or accurate. We have created a tutorial illustrating some methods of keeping cemented segments safely in place while waiting for the adhesive to cure. See the link or click on the photo on the right.
If you are working on small items that can be secured quickly, the quick setting 5 minute epoxy may be your choice. Spreading glue over larger items may require a slower setting of the product. Five minutes go by fast! Slower-setting epoxy is generally stronger, although some brands have recently improved the strength for fast-setting epoxies to be as good.
Applying 2-part epoxy
High Temperature Failure Superglues are fairly resistant to heat, but their strength will be reduced. It is not recommended for applications where the glue may be exposed to temperatures over 200 degrees F. The bond will deteriorate with heat..
Most epoxies can withstand temperatures up to 2000 F (900 C). Anything higher and the molecular structure will change, causing the epoxy to soften.
Cover full surface
Repair Line Thickness and Color Super glues leave a thinner mending line while some epoxies have color; some are clear and others are yellow, but they all leave a thicker line. Therefore, consider appearance in your selection of epoxy. If further restoration is planned, (i.e. hiding repair lines with fillers, colors and cold glazes), select the stronger epoxy regardless of color.
Place and apply pressure
Note: Lakeside Pottery Studio uses 3600 PSI clear epoxy (see link) for most mending applications. Most clear mending epoxies turn yellow with time when exposed to UV light (e.g., sun or fluorescent light) and can impact the quality of the over-painting restoration effort.
Removing epoxy later
Cleaning We recommend not to attempt to clean excess epoxy while it is still liquid to avoid lining shift and smearing onto a larger surface area. Let the epoxy cure partially to ensure a stable bond before removing excess cured epoxy with a blade (see more). Epoxy spillover on soft ceramic (e.g., terra cotta) is undesirable. In removing the excess epoxy you will likely scratch soft ceramic or stone and cause further surface damage.
Conclusion Lakeside Pottery Studio prioritizes the durability, longevity, and aesthetic quality of our ceramic and sculpture repairs, which aligns with the need for high-quality materials like clear epoxies over super glues. Super glues are just not strong and durable enough and are not suitable when used with a seamless repair given their interaction with other materials such as fillers and paints.
In most of our ceramic restoration, we invest significant effort in hiding the repair and therefore have to make sure the mending longevity and visual performance are the best possible and will last indefinitely.
We use high-end, non-yellowing 5 minute clear epoxies (see link for the brand we do use) in most ceramic, stone and Kintsugi repair applications.
Super glues are probably a good choice for items that are not handled often, without long life expectation and subsequent layers of other materials are not applied over the mending areas.
How To Repair Broken Pottery - Video
This lesson shows only the highlights and is not a DIY lesson
