A good clear glaze should do one thing exceptionally well: disappear. It should leave behind a smooth, glossy surface that enhances your pottery while allowing the clay body or underglaze colours beneath to shine through.

Whether you're glazing bare clay or protecting vibrant decoration, a well-chosen clear glaze can transform the finished piece. At Kiwi Underglaze, we've tested our colours beneath countless commercial clear glazes over many years. While every clay body, glaze and kiln combination behaves a little differently, the principles below consistently produce excellent results.

1. Start with a Clean Surface

Before glazing, make sure your pottery is completely dry and free from dust, fingerprints, grease or other contaminants. Even small amounts of residue can interfere with glaze adhesion and lead to defects after firing.

2. Always Test First

Whenever you're using a new clay body, glaze or firing schedule, make several test tiles before glazing important work.

Test tiles allow you to evaluate glaze fit, clarity, colour response and surface quality without risking finished pieces. They can also reveal compatibility issues between your clay body and clear glaze before they become a problem.

If you're using Kiwi Underglaze, it's worth testing your chosen clear glaze over several colours. Some clear glazes perform beautifully over every colour, while others may behave differently depending on the clay body, glaze thickness and firing schedule.

3. Mix Your Glaze Properly

Consistency is one of the keys to achieving reliable glazing results. Always mix your glaze thoroughly before use, ensuring any settled materials are fully incorporated.

If you're mixing from powder, begin with the manufacturer's recommended water ratio and adjust only if necessary. Because every glaze formulation is different, there is no single ideal mixing ratio. Sieving the glaze before use can help remove small lumps and produce a smoother, more even finish.

4. Apply Evenly

Whether you're dipping, pouring, brushing or spraying, aim for an even glaze layer over the entire surface.

If you're applying a clear glaze over underglaze decoration, uneven glaze thickness will often be much more noticeable than it would be over plain clay. Taking a little extra care during application can make a significant difference to the final appearance.

Once the glaze has dried, remove any excess from the foot and smooth out heavy areas before firing.

5. Apply the Correct Glaze Thickness

Rather than focusing on the number of coats, concentrate on achieving the correct overall glaze thickness.

How you reach that thickness will depend on your application method. Dipping and pouring often require only a single application, while brushing and spraying typically involve building the glaze in several lighter coats. Applying the glaze too heavily can increase the risk of runs, cloudiness, blistering and other surface defects, while applying it too thinly may result in a dry or patchy finish.

6. Pay Attention to Your Firing Schedule

Your firing schedule can have a significant influence on the final appearance of a clear glaze. Even with the same glaze, changes to the firing profile can affect gloss, clarity, bubble release and the overall surface finish.

Two techniques that many potters have found particularly effective are a soak at peak temperature and a drop-and-hold cooling cycle.

A short soak at peak temperature gives the glaze additional time to fully mature while allowing any remaining gases to escape before the glaze begins to stiffen. This can help reduce pinholing and blistering, particularly in clear glazes.

A drop-and-hold involves cooling the kiln to a lower temperature before holding it for a period of time. This keeps the glaze fluid for longer, giving the surface additional time to level out and heal before it solidifies. Many potters find this produces a smoother, glossier finish with fewer surface imperfections.

During the development of Kiwi Underglaze, we've carried out extensive testing beneath a wide range of commercial clear glazes. Time and again, we've found that small adjustments to the firing schedule—particularly the use of a soak and, where appropriate, a drop-and-hold cooling cycle—can significantly improve the finished surface.

Every glaze, clay body and kiln behaves differently, so there is no single firing schedule that suits every situation. Begin with the glaze manufacturer's recommendations, then make small, controlled adjustments using test pieces to evaluate the results.

7. Prevent Blistering and Pinholing

Blistering and pinholing are among the most common defects encountered with clear glazes. They occur when gases become trapped beneath the glaze surface as it begins to stiffen during firing.

Possible causes include glaze applied too heavily, thick applications of underglaze beneath the clear glaze, gases released from the clay body late in the firing, incompatibility between the clay body and glaze, or a firing schedule that doesn't allow sufficient time for gases to escape before the glaze sets.

If blistering occurs, don't assume the glaze itself is at fault. Through our own testing, we've found that firing schedule adjustments often resolve blistering more effectively than changing glazes. Before assuming a glaze is incompatible, it's well worth experimenting with a short soak at peak temperature or a drop-and-hold cooling cycle using test pieces.

8. Keep Your Glaze Clean

Avoid introducing clay, underglaze, plaster or other contaminants into your glaze bucket.

Use clean brushes, tools and containers, and sieve your glaze periodically if necessary. Even small amounts of contamination can affect the finished surface.

9. Keep Good Records

One of the fastest ways to improve your glazing results is to keep accurate records. Whenever you achieve a finish you're particularly happy with, note the clay body, glaze, application method, glaze thickness, firing schedule and kiln used. Equally importantly, record the details when something doesn't go to plan.

Over time, these records become an invaluable reference, allowing you to identify patterns, repeat successful results and troubleshoot problems with far greater confidence.

Every Kiln Is Different

There is no single "perfect" clear glaze or firing schedule.

Every combination of clay body, clear glaze, kiln and firing programme behaves slightly differently. The key is to make small, methodical changes, test thoroughly and build an understanding of how your materials work together.

At Kiwi Underglaze, we've helped thousands of potters troubleshoot clear glaze issues. While every studio is different, careful testing, consistent application and a well-developed firing schedule will almost always produce better results than constantly changing materials.

If you're using Kiwi Underglaze beneath a clear glaze and you're experiencing blistering, cloudiness, pinholing or other surface defects, we'd love to help. Get in touch with our team and we'll do our best to help you achieve the beautiful, durable finish you're looking for.