Fortunately, these glaze imperfections can be addressed. Let's take a closer look at what the consequences of applying too much glaze to pottery can be and what you can do to resolve them.

One of the most likely things that can happen to pottery if you apply too much glaze is that the glaze will run when fired.

Glazes melt when fired. The silica in the glaze becomes liquid when it gets hot enough and forms a molten layer on the glaze. As the pot cools, the glaze solidifies again, forming a shiny, glassy surface.

Some glazes are described as ‘hard’ or ‘inert’. These are glazes that do not move much when fired. Other glazes are very fluid and form dripping patterns. Fluid glazes are often layered with each other to create lovely dripping mixed patterns on the pottery.

Drips and runs can be an intentional part of the glaze look you want. But if your glaze flows excessively, you will probably run into problems.

One problem might be that the glaze runs all the way to the base of the piece and sticks the pot to the kiln shelf. Or, if you are firing something with a lid, the lid may stick to the piece.

If you have applied too much glaze to the inside surface of the piece, the glaze can run and pool at the base. When this happens, bubbles can form, trapped in the accumulated glaze.

Factors that affect whether your glaze will run:

Some glazes flow a lot, even when not applied thickly to a piece. These glazes contain high amounts of plasticising oxides. Plasticisers lower the melting point of the glass-forming components in the glaze.

Other glazes will flow when layered with other glazes. The combination of the two glazes changes their chemistry and causes them to become more fluid.

Another factor affecting whether the glaze will run or not is the thickness of the application. Even a very stable glaze can run if it is applied too much on the pot.

Solution of Flowing Glaze

If you have purchased a commercially produced glaze, pay attention to the manufacturer's instructions on how many coats should be applied.

The first time you use a glaze, it is a good idea to bake a test piece first. You can get an idea of how fluid your glaze is by looking at the test piece.

When using a new glaze, leave a good margin when wiping the base of your pot before firing. It will be enough to wipe about 1cm.

If you are sure that the glaze is too thick and you do not want to risk it running, you can wash it off and start again. However, you must make sure that the washed piece is completely dry.

Climbing

Climbing also occurs when the glaze is not well bonded to the biscuit surface. This can also be the result of applying too much glaze to the pottery. Glaze materials are suspended in water. When you apply glaze to the pottery surface, water is absorbed into the porous biscuit. As the water is drawn through the glaze, the glaze forms a bond with the pottery surface.

If you apply too much glaze to your piece, the biscuit can become overloaded with water. When the biscuit is too wet, it can prevent the glaze from forming a strong bond with the surface.

Sometimes it is obvious that this has happened and the glaze is poured off in pieces before baking. However, every now and then the glaze will have a smooth appearance and will appear to stick to the pot.

In fact, there is a gap between the glaze and the surface of the biscuit. Therefore, the glaze hangs on the biscuit. When baked, the glaze will peel off from the patches where it does not stick.

Solution for Cracking, Shedding and Climbing

The glaze on the pottery should be ‘credit card’ thick. Getting this thickness depends on how you apply the glaze.

Glaze Dipping

If you are dipping your piece in sequence, it is common practice to dip the pot for about 5 seconds. However, it may vary depending on the row you are using. You can learn by experience or consult with the manufacturer.

It is not necessary to dip the pot into the glaze twice. If you plan to dip twice, make sure that each dip is short. For example, two dips of 2 seconds each. Double dipping is usually done to layer two separate rows on top of each other.

Glaze Application

In general, it is recommended to apply 2 or 3 coats of brush glaze. When applying the glaze with a brush, be careful not to get too much glaze on the brush and not to apply too much at the corners and joints.

For example, too much glaze is likely to collect where a handle meets a mug. This can cause cracking in some glazes where the glaze is thicker.

Also, allow the first coat to dry a little, but not completely dry. If the first coat dries completely, when you apply the second coat the moisture in the second coat can loosen the bond between the first coat and the biscuit.

Likewise, it is best not to apply the second coat too early. If there is still a lot of water in the biscuit from the first application, the second coat may be too thin. It can also take a long time for the glaze to dry. This can cause the glaze to crack and form a poor bond to the biscuit surface.

Glaze Pouring

If you are pouring the glaze onto your artefact, a single pour is usually sufficient.

Bubbles:

If gas bubbles are trapped in the glaze before they reach the surface, the glaze may appear cloudy. This is especially a problem with transparent glaze over coloured clay or glaze over slip.

For example, if you apply a transparent glaze over red clay, the bubbles in the glaze will look milky on clay soil.

Blistering:

Sometimes gas bubbles can rise to the surface of the glaze, but then become trapped just below the surface. This can form a bubble in the glaze. Sometimes these have a very thin film of glaze that breaks when the pot cools or is handled. It is important to handle them carefully as the bubbles are often sharp.

Other times the bubble will burst in the kiln, but will leave a mark on the glaze surface if it does not have time to heal properly in the glaze firing.

Solution to Blisters and Blisters:

Bubbles in the glaze can occur for various reasons. This may not always be related to the thickness of the glaze surface. And sometimes it will be a combination of several factors, including the thickness of the glaze.

If bubbles and blistering occur on your pottery, you can try applying a thinner layer of glaze. It is also true that some glazes are more prone to blistering. For example, hard glazes are more likely to bubble.

Glazes that are fluid allow bubbles to escape quickly. After the gas has escaped, the mobile glaze quickly heals and becomes smooth. In contrast, hard glazes have higher surface tension and it is more difficult for bubbles to escape

The combination of the coarse texture and the gases emitted from the clay body during firing can create bubbles on the pot, which in turn create pinholes.

However, pinholes can also form when a very thick glaze is applied. Pinholes in thick glaze form like bubbles. Bubbles in the glaze released from gases take a very long time to pass through the thick glaze. When the bubbles reach the surface they burst, but the glaze does not fill the hole left behind.

Pinholes differ from bubbles in that they do not have the same fine glaze bubbles above the hole. They are also smaller. The larger the pinholes, the more this is classed as climbing.

The best way to find out how many layers of glaze your pottery needs is to glaze a test piece. Scrape off the glaze with a needle tool or cleaning tool and see how thick it looks after subsequent layers. You can also fire your test piece to see what the fired glaze looks like.

When these fractures are tiny cracks on the cookware, they will appear as cracks in the glaze. Thick glaze cracks more easily because the layer is stronger and under more tension.