How To Fix Broken Ceramics

A broken ceramic or a piece of broken pottery can seem like a disaster, particularly if the piece has sentimental value or you are looking to sell the piece.

The most effective method of fixing cracks and missing pieces on a broken ceramic object is by using a cold-materials process.

This can involve materials such as adhesives, fillers, paints, and glaze. With some of these materials at hand, you can easily repair broken pieces or repair lines on your ceramic piece.

Fixing broken ceramics happens in two stages. The first stage is to actually fix the broken piece or gaps in the ceramic and the second stage is filling and sanding any visible break lines, chips, and gaps using a variety of materials. This basic process of putting ceramics back together or repairing a broken piece of pottery is more suited to non porous materials such as stoneware and porcelain.

What do you need to fix broken ceramics?

The materials you require are fairly simple. One of the key items is a good quality ceramic glue, as without the necessary bond, your ceramic repair will not work well and your ceramic pieces will not bond properly.

Probably the best and most suited adhesive is a clear, five-minute setting, two-part epoxy. However, to choose the best ceramic adhesive for your repair, you need to consider the type of ceramic you are going to fix.

A five minute epoxy might set too quickly if the material you are working with proves difficult to get an exact match between two pieces. Some clays such as terracotta require epoxy on both sides and a slight heating in order for the bonding to occur effectively. You can use super glue, but it doesn't always create the clean and strong bond that you are looking for.

Here are some of the key materials that you will need for the fixing part of the process:

1. 5 min PC Clear epoxy
2. Wooden stick or a pin-tool
3. Container with plastic pebbles or rice
4. Razor blade
5. Denatured or 91% Alcohol
6. Rag
7. Paper pad to mix Epoxy on

Preparing the surface of the broken ceramic

Perhaps the key part of the process is to ensure that the surface of the broken ceramic is clean and free of any debris. If you have attempted to repair the piece before, make sure that you remove any old adhesive so that the pieces fit together as was originally intended.

There are various cleaners available on the market that can remove a variety of historical stains or old glue. You can also mix acetone or lacquer thinner with cured 2-part epoxy as a great general cleaner. To ensure the surfaces are completely clean, use the denatured alcohol to ensure any old stains are completely removed.

Before starting to undertake your repairs, you should fill a container that is larger than the piece that you want to repair, with plastic pebbles, rice, or sand. This will ensure that the repaired piece does not move around whilst drying and ensures a strong bond. Before you commit to bonding, undertake a dry fit of the pieces to check how you want them to fit together.

How to mix and apply glue to your piece

Firstly, place a few small amounts of your five-minute, two-part epoxy on your paper or cardboard pad. Next, you should mix the epoxy well with your wooden stick. Using the wooden stick, then apply the epoxy carefully to one of the broken edges of the ceramic. Be careful to only apply epoxy to cover the broken edge as you do not want lots of excess adhesive covering other parts of the piece .

Basically, if you apply too little adhesive, it will leave gaps in your piece and you won't achieve a strong bond and therefore a poor repair that won't last. If you use excess epoxy it will mean it is difficult to achieve a tight joint to cracks.

A good idea is to warm the broken pieces to 90–110°F, which will thin the epoxy and create a smoother and neater fit, however the drying time will speed up, so you need to make sure that the fit is perfect.

Next, work quickly to join the pieces together, applying a small amount of pressure to squeeze the excess epoxy out. If you are working with very small pieces, use tweezers to increase the accuracy of your repair.

You need to work quickly as you will have just over a minute from when you mixed the epoxy to the repair being put in place before the epoxy becomes too sticky and unworkable. If gravity does not hold the pieces together, you can use clay to help encourage the bond.

If you do have any epoxy that has escaped from the joint, it can be removed later on using a razor blade.

What if my piece has multiple breaks?

With a piece that has multiple breaks, you need to plan out the object before committing to sticking. Otherwise, you may be left with a piece that doesn't fit. A good tip is to label or number the pieces, which makes it easier to fit them together when you come to finishing the real piece. You should let each piece dry before attaching the next one, otherwise everything will be knocked out of place.

How to fill and finish your broken ceramic

Once the piece has been repaired, you are going to want to fill any lines and sand them out so that the fix appears seamless.

There are a number of good filler products on the market. PC-11 filler epoxy is perfect for filling in very small missing pieces and visible repair lines. A good filler will offer strong adhesive qualities and won’t shrink while drying.

It should also be workable with ease of application, and the ability to be drilled, sanded and paintable. Finally, it should be able to tolerate heat without shrinking or losing any of its properties.

You should make sure that the filler will cure to a very hard state so that it can be easily sanded and finished. Finally, make sure that you wipe the surface with your 91% alcohol solution to remove any dust or oils prior to applying your epoxy.

To make life easier at this stage, work in a warm room which will make the filler easier to handle.

You should allow filler epoxy to cure for at least 12 hours in a warm temperature environment (ideally 75 degrees or above). You could also use a kiln heated to 110°F, keeping the object in there for 8 hours.

Alternatively, if you want to save energy, place the item under a lamp to create an extra dry surface for sanding. Using a 120 grit sanding disc, sand down any extra surface epoxy that has formed. You should only use a sander on a low speed to avoid burn marks and only apply light pressure.

If you decide to sand by hand, start with 220 grit paper and finish with 400 grit paper. You might come across more cracks at this point, so just repeat the process. At this point, clean the piece with your alcohol mix to remove any imperfections.

Filling in for larger missing chunks

For any larger missing pieces, you are going to need to fill them with wet clay. Work the clay so that it perfectly matches the height and surface of the surrounding area and let it dry thoroughly. You should then fire it in a kiln to bisque temperature.

You might want to allow for shrinkage, but once cooled and dry, attach it to the piece with epoxy. Carefully sand the edges to make sure that the fit looks fairly seamless and fill in any remaining gaps with PC-11. Let the whole thing dry before repeating the sanding process above.

Final touches

After the repairs and sanding has taken place, you may need to finish with a little paint to match in the color and style of the piece. Matching the color and texture of the piece is one of the hardest things to master when repairing ceramics. If the color and texture don't match perfectly it will be obvious. To make a color match perfectly, you need to take into account that colors can look different when dry, so it's best to experiment before applying to the final piece.

Summary

An effectively repaired ceramic can be highly pleasing. Carry out the process well enough and any damage can be virtually undetectable to the naked eye. To get the best effect, it's important to use the very best raw materials and ensure that your repairs cure properly at each stage.

In order to hide the repair lines, time should be taken to sand and polish with several different grit sandpapers to ensure that perfect finish.