How to repair Kiln-fired pottery
during the construction process
Hello. My name is Kathie, a pottery-making novice and enthusiast.
My creations often stretch the boundaries of the medium. Truly, the most common remark I hear during the design process is: “throw it away and start over.” However, my background in painting and sewing has a different mantra: “you must always finish what you begin.” I prefer the latter.
Safety first. For this reason, never risk firing something that is not routinely put in a high temperature kiln. Doing so can emit unexpected toxic fumes, cause fires, or even explosions. With safety in mind, I developed methods that have been extremely successful at repairing broken greenware. If a creation breaks, try the following steps:
Wet both sections of the clay that you want to attach, a spray bottle filled with water works perfectly
Make a slip using only water and clay
If the break is smooth, score both sides; if the break is jagged, no need to score
Apply a small amount of slip to the internal break on both sides
Press together tightly and apply a clear 4-6 cone glaze liberally on all sides of the repairs. Hold tightly or push between two heavy objects until thoroughly dry
After drying add a thin layer of slip; when this dries, add another layer of glaze
Attach wet clay around all edges, thoroughly blending the new clay into the old clay
After this dries, coat with another layer of glaze
Be sure the glaze is not on the bottom of the piece when firing! I believe this method works because, when fired, the glaze “fuses” into the repair and strengthens the bond. However, it isn’t true science and may take a couple of attempts before you're ready to fire. Sometimes the repair is successful after completing only steps 1-5 and skipping to step 8 (depends on the location). Have you ever tried to open a jar of glaze that would not budge? You run an ounce of water on it and Voila! - it opens instantly. Keep this in mind, because before the mended greenware has been fired, the repaired area is extremely fragile. Afterwards - it’s strong!
The above method has not been routinely successful at repairing broken bisqueware. If a break occurs on the top of a creation, use the tried-and-true method of attaching the broken piece with glaze and fusing it together in the bisqueware firing. However, we all have pieces that break from the bottom or side of our creations and the tried-and-true method will not work. Glaze these pieces separately and permanently attach them afterwards using the following methods:
If your creation has cracked, or is uneven on the bottom, fill or repair the area with Minwax stainable wood filler; it will become extremely hard and dry the color of clay
If your creation breaks in areas requiring more stability, attach the two pieces with enamel putty. This is available in wood putty, marine putty (often white) and black putty. Just visit your local Lowes adhesive department, be sure to read and follow all directions carefully. Do NOT fire these adhesives!
If the putty does not match your glaze, touch up with porcelain paint markers (available from Amazon), let dry, then spray with craft Krylon
Porcelain paint markers are non-toxic and can be used on non repaired creations and fired in your oven to correct glaze mishaps or add glazed effects to already glazed pieces
Disclaimer: Although some repaired pieces may have strength comparable to intact pieces, I can’t condone selling them except as ornamental “seconds”.
Well Stan, I almost threw this little guy away. But using prior surgery methods that I included in the article I wrote, he survived. I used porcelain glazes that fire at 375 degrees to spruce him up because I can’t yet fire my kiln.
Good luck and have fun creating!!!
This lizard was in 3 pieces after an inattentive driver almost side-swiped me; when I swerved to avoid the accident, it flew across the car!
The bottom of this frog was uneven by over 3/8 inch and filled with wood filler.
The left leg of this frog was reattached with black enamel putty then touched up with porcelain pens.