Category Archives: Crack

Best stage of clay to fix a crack

I believe that most of the time when we don’t have a good result, it is not because we didn’t use the right product or formula it is because the piece was in a different stage of dryness. Below are some simple ways to understand the stage of the clay when you make a piece.

Characteristic Stage of the clay
Sticky Plastic
wet, but not sticky Leather Hard Soft
feels cool and stiff Leather Hard Stiff
room temperature ready to fire Bone Dry/Green ware

The perfect stage of clay to fix a crack or join together is leather hard soft. To return from leather hard stiff  to leather hard soft you have to cover the piece with a wet paper towel then cover with plastic , then wait a least 1 day.


But you have to remember if your piece is bone dry/greenware it is not easy, it will be require a lot of patience to return your piece to earlier stages. Sometimes when I try to wet the piece and cover it with wet paper and plastic  for one day it is not enough,  I have noticed the surface is wet but not the internal part, especially if it is thick.  You have to repeat the process again until the piece is leather hard soft.


What do you use to fix a crack or join pieces?

I tried many different recipes and products to join and repair pieces. My goal was to find what works for each stage.  I struggled with commercial products. Most of my pieces are complex in structure and thickness I believe the products work, the pieces were attached, but I have problems later.

Stop the crack before you fix it
Something that I tried is to make perpendicular lines at the ends of the crack before I fix it. If you don’t do it the fissure tends to keeps going creating very thin hairlines at the ends. I saw that in porcelain because it is more unforgiving.


I tried  slip, Paper clay, Bone dry clay with vinegar, Miracle water, Sodium Silicate, Commercial products. Below are the best results in each stage of the clay.

Plastic (Stage of the clay)
√ slip

In the plastic stage it is easy to join. The same clay with out water can work too.

Leather hard Soft (Stage of the clay)
√ slip
√ Paper clay
√ Bone dry clay with vinegar
√ Miracle water or mender
√ Miracle water Sodium Silicate
√ Commercial products

Leather hard Soft is perfect to repair and join, This is the process to attach two parts:  1. score both parts.  2. use your mender on both parts. 3. Put a coil of soft clay between both parts.

Leather hard Stiff (Stage of the clay)
√ Paper clay
√ Bone dray clay with vinegar
√ Miracle water
√ Commercial Products

To repair and join at Leather hard Stiff , I wet the two pieces and cover with wet paper and plastic. Then wait until the two parts are in leather hard soft.

Bone dry/ Green ware (Stage of the clay)
√ Miracle water
√ Miracle water Sodium Silicate
√ Commercial products

When I join and repair in Bone dry stage, I have to fix it more than once. In porcelain pieces sometimes repairing takes more than 4 times, it is time consuming. Apparently good results in the bisque fire, the pieces are attached and cracks are fixed, but in the second fire you see the glaze shivering, the glaze peels off showing the crack.


After Bisque cone 04  (Stage of the clay)
√ Paper clay
√ Miracle water
√ Commercial Products

Most off my pieces that I fix after bisque and  re-fire to cone 04 with or without  candling the piece, the clear glaze on top starts  shivering too.


Using only Sodium Silicate leaves orange color and you  can still see the fissure.


I know I’m learning,  this is not about restoring, my emphasis is about finding the way the save pieces that are difficult to make again. Using the right mender in the best time. Nevertheless I find the best of all for me was paper clay in leather hard soft stage. Less ingredients in your mender is better, there are less chances of altering the process of fire and  glazing.

I tried to improve the results of my slips, using bone dry clay hammered into small pieces and less water. Blend in electric blender,  wait one day.

Very good article about deflocculation slip

Magic Water Recipe
1 gallon water
3 table spoons of liquid sodium silicate
1 1/2 teaspoons of soda ash
Lana Wilson recipe

Paper clay Recipe
1 cup bone dry clay
1 cup water
4 pieces of toilet paper
Blend in electric blender
After one day sometimes I drain away the excess water
Rosette Gault recipe
Martha Grover recipe

Good article about Paper clay