Helpful Hints for Magic Mender:
While the mender is still moist, the joint will be fairly delicate, so be careful when cleaning the mold. The Menders must be fired to become permanent. Keep unused portion in jar tightly closed. The mender has a long shelf life and will not spoil! After firing, the repaired area is stronger than the rest of the mold. If you clean well before firing you’ll never know the break was there.
How to fix hairline cracks:
Use a knife tool or dermal to open the crack. (You must get the mender deep into the crack for it to work, otherwise the crack will reappear.) Dip a brush in the mender and in some water so that you have a flowing consistency. Allow the mender to flow into the cracks, then let dry. If you need a second application, do so, then clean the mold and fire.
#2. You can also use a resin based cement that is used in kiln building called "Sairset". It should be available in all ceramic suppliers. Make the edges to be joined wet. Spread some Sairset on the joint. Wipe all of it off the working surface with a wet cloth or sponge. Back up the repair with more Sairset on the back. Wash all tools used immediately or the Sairset will never come off. When dry, fire to about 800C. , then wash the mold and you are ready to go.