The newspaper will almost completely vanish, leaving next to nothing left. While the little amount has no effect on the work in the kiln, it does wear down the elements of the work done on a continuous basis. This includes glazes and paints that are used to decorate terra-cotta pieces.
However, because this is an oil-based product, water has an extremely detrimental effect on its durability. So if you plan to fire your piece using this method, then it is recommended that you do so in a dry environment without any moisture present.
Clay also absorbs oxygen from the air when it's not being fired. If you leave a clay object out in the open air, it will eventually crumble due to oxidation. This is why most pieces have some kind of base or support when they're being displayed or used. Without such a support, they would be weak and likely break under their own weight or when hit with another object.
Finally, heat can damage some materials. When firing clay, you need to make sure that you don't go over 100°C (212°F) because this will cause the material to decompose.
In conclusion, yes, you can fire clay with newspaper inside but only if you intend on keeping it intact after firing.
As the kiln heats up, the leftover water evaporates from the clay and turns into steam. If heated too quickly, it may convert to steam while still trapped in the clay, causing the pot to explode! It's important not to fire wet pots until they are completely dry.
If an air pocket enters the kiln, your item may crack, break, or even explode depending on the size of the air bubble and the circumstances, but your kiln should be unharmed. Kilns are designed to resist the explosion of pottery. Cracks, breakdowns, and blowups are natural occurrences in the craft. However, if a large enough piece of broken/exploded pottery gets into another part of the kiln, it could start other pieces breaking down as well.
Kilns are not like freezers where you can leave openings for air to enter. All openings must be closed either by using ceramic glazes, paints, or stains or by covering them with paper or cloth. This is because heat travels through ceramic materials very easily and any opening that allows air in or out will cause different parts of the pot to dry out more quickly than others. This can lead to cracking and other damage.
Items that tend to have more problems with air bubbles include bowls, jars, platters, and vases. They are usually thicker at the bottom and thinner at the top, which creates more opportunity for cracks to form. If you own any of these items, make sure to fully seal your pots before putting them in the kiln.
Now that you know about what can happen if you have air pockets in your clay projects, be sure to follow proper sealing techniques to avoid potential damage to your kiln.
The most important thing to keep in mind is not to over-fire! (This is in contrast to glaze, which must be burned to the specific temperature range stated.) If you over-fire clay, it will first slump and bloat, then melt and perhaps cause significant damage to your kiln. Under-firing can also be a problem if you leave the fire too low; then the clay will not dry properly and may even catch on fire.
Clay needs to be fired at a high temperature for a long time to burn off its moisture content. The amount of water that can be driven out is called the "dry density." Denser clays can be fired to higher temperatures before they scorch. Looser clays may need more time or heat reduction before they are dry enough to use again.
There are two types of firing: greenware and brownware. Greenware is still moist from the mold when it is fired, so it must be kept in a dry place with plenty of air circulation. It should not be placed in an oven without being protected by a glaze or coating material. Greenware usually needs to be fired at lower temperatures and for a shorter time than brownware. That's because the moisture in the clay vaporizes at a lower temperature, and it can escape through the open pores of the pot. As long as the pot has openings for smoke to come out (such as a handle), it is safe to fire greenware.
It cannot be burnt in the kiln until it is completely dry; otherwise, it would distort or shatter in the kiln. Drying your greenware with care ensures that all sections of the piece are dry and that it dries evenly. It is critical not to force-dry pottery by blowing hot air upon it to speed up the drying process. This can cause the piece to crack.
Clay is in its best condition when it is fresh and has a fine powdery texture. It should not feel gritty when pressed between your fingers. If you use very old or very new clay, the colors may not be as intense and the pieces will likely need more time to dry before they can be fired.
If you insert a lighted match into the base of a jar filled with wet clay and pull it out again, the flame indicates that there's still water inside the jar. It's safe to say that the clay is not ready yet because more time is needed for it to dry out completely. When the flame dies down, remove the jar from the kiln and let it cool down before opening it. If you do not, the heat from the flame could damage the seal on the top of the jar.
In the kiln, your glazes may flake and break as well. An unfired piece of work is also more brittle than a fired piece of work, thus you run the danger of injuring it during the handling process when applying the glaze.
When clay is wet, it's much softer and more pliable. If you try to roll it out into a shape, it will be difficult because it won't hold its form. But once it dries, the clay hardens and becomes more rigid. You can still work with it then because the drying process has removed most of the water from the object.
So, putting glaze on an unfinished piece of pottery is not recommended because it will not stick and could fall off during the firing process. But you should know that this method produces unique results very different from using glaze on a finished piece of pottery.
When firing without a kiln, pre-drying your clay pieces in a home oven set to 190 degrees F may assist. The pots are dried in a home oven by "baking" them below the boiling temperature of water for many hours. I preheated the oven to 190 degrees Fahrenheit. Then I placed each pot on a baking sheet and put it in the oven for about 10 hours.
Clay is a natural product that will absorb any moisture that finds its way into an unglazed pot. If you leave your pot outside in the rain, it will eventually become wet and sticky. This means that it will be harder to fire properly. To keep your pots safe from weather damage, either glaze or seal them. There are several ways to do this. You can use a clear acrylic paint which can be bought ready-to-use or make your own using white wood glue and clear nail polish as a base. The pot can then be exposed to the atmosphere for several months before being painted.
If you choose to seal your pot, first apply a thin layer of oil to the inside and out. Let it dry for at least 24 hours and then sand it with fine sandpaper until you get back to the original color of the clay. You can then wait another month before painting or sealing again.
Home drying is useful if you want to fire your pots quickly without having to go to a studio or save some money on fuel.