Unfired Clay: Unlocking the Secrets of Glazing for Perfectly Finished Ceramics

I do not recommend to glaze unfired clay. Glaze is a type of coating that applies to clay after firing. If glaze applies to unfired clay, the moisture in the clay can cause the glaze to crack or blister during the firing process, ruining the piece. It is important to let the clay dry completely before firing and glazing to ensure the best results.

Gleaming Glazes: How to Transform Unfired Clay into Stunning Ceramic Artwork

Now, all that being said above, it can be done. I just do not recommend this process for beginners.

Some (experienced) potters do coat unfired clay with glaze, especially low fire clay. The term “bisque firing” or “biscuit firing” is frequently used to describe this method. To harden the clay and remove any residual moisture, bisque firing involves firing it at a low temperature. In order to enable the glaze to penetrate the clay’s surface, it is then glaze while it is still porous and unsealed.

It is important to keep in mind, though, that this method has its drawbacks and dangers. In order to prevent the glaze from cracking or blistering during firing, the unfired clay can take moisture from the glaze. Furthermore, the bisque-fired clay needs cautious handling to avoid breaking because it is more fragile than fully-fired clay.

Some potters continue to use the bisque firing method despite these difficulties due to its distinctive visual benefits. The porous surface of the bisque-fired clay can produce intriguing shapes and designs in the glaze, as well as a softer, more matte finish. Use of this method will ultimately rely on the artist’s preferences, the kind of clay and glaze being used, and the final result of the piece.

What Is Single Firing Or Glaze Firing?

After the glaze has been applied to the unfired clay, the clay is only fired once in the single firing pottery method. In contrast to the conventional two-firing method, which involves firing the clay to bisque (a porous, unglazed condition), glazing it, and firing it again to produce a finished, glazed piece.

Because both methods require applying glaze to the unfired clay, single firing pottery and glazing unfired pottery are related. The glaze is applied straight to the unfired clay in a single firing, and the piece is fired just once at a higher temperature to fuse the glaze and clay together. In addition to using glazes that are formulated to be compatible with the particular clay being used, this necessitates careful firing process control to guarantee that the clay and glaze are heated uniformly and to the proper temperature.

On the other hand, glazing unfired pottery is frequently done as part of the conventional two-firing procedure. To create a finished object, the clay is bisque fired to a porous state, then glazed and fired again at a higher temperature. The firing process can be more precisely controlled, and any problems with the glaze coating can be fixed before the final firing.

Which method to employ relies on the potter’s objectives for the finished object, the properties of the clay, and the glaze being used. Both techniques have benefits and drawbacks. Single firing can reduce effort and time consumption while producing distinctive effects in the final piece, but it takes more expertise and experience to carry it out effectively. Unfired pottery can be more precisely controlled and error-corrected by glazing it using the conventional two-firing method. However, this method can take longer and produce subtly different aesthetic results.

Glazing Firing Advantages And Disadvantages

There are benefits and drawbacks to glazing unfired clay, also known as bisque firing. Here are some of the most important ones:

Glazing Firing Advantages

  1. Due to the porous nature of the clay, bisque firing can produce distinctive and intriguing textures and designs in the glaze. This can give a piece more substance and personality.
  2. A softer, more matte finish can be achieved by allowing the glaze to penetrate the clay surface more thoroughly.
  3. Bisque firing can be carried out at a lower temperature than a complete firing, which can reduce time and energy consumption.

Glazing Firing Disadvantages

  1. Clay that has not been fired is more fragile than clay that has been completely fired, so it needs to be handled carefully to avoid breaking during glazing and firing.
  2. Furthermore, if the glaze is applied too thickly or contains too much water, the porous structure of the bisque-fired clay can make it more prone to cracking or blistering.
  3. A less durable final piece may result from the glaze adhering to the bisque-fired clay less effectively than it would to fully-fired clay.

So why would an artist choose to employ this method? It might be because of the above-mentioned distinctive aesthetic characteristics. By firing at a lower temperature, bisque firing can also be a method to save time and energy. The suppleness of the matte surface that comes from bisque firing is also preferred by some potters. In the end, the choice to employ this method will be determined by your objectives for the finished object as well as the properties of the clay and glaze being used.

Glazing Firing Challenges And Solutions

Glaze firing pottery can offer a number of difficulties, but potters can use these issues as a springboard for other, more manageable issues. Here are a few instances that come to mind:

Problem 1: Glaze that drips or runs is the first issue.
Solution: Use a glaze that is less fluid or apply a thinner layer of glaze. Alternatively, you might try spreading the glaze on in a number of tiny layers, allowing each one dry before moving on to the next. You can attempt to wipe away a drip or run with a sponge or tool before it dries, or you can sand it off after firing, if it does happen.

Problem 2: The glaze’s cracking or burning
Solution: Too much water in the glaze or firing too fast can both contribute to this problem. Make sure the glaze is the right consistency and the pottery is fired at the right temperature and rate to prevent this. Making ensuring the pottery is completely dry before firing is also crucial.

Problem 3: Pinholing or blistering in the glaze is issue number three.
Solution: Gases escaping from the clay during firing are one possible reason of this. Ensure that the pottery is bisque fired at the proper temperature and rate to prevent this. You can also try making sure the pottery is not too thick or adding a vent hole, both of which can help release trapped gases.

Problem 4: Crazing is the fourth issue (cracks in the glaze)
Solution: A discrepancy in the expansion and constriction rates of the clay and glaze may be the root of crazing. Use a glaze that is appropriate for your clay and firing temperature to prevent this. To lessen the strain on the glaze, you can also try changing the cooling procedure after firing.

Problem 5: Fifth issue: The glaze isn’t sticking to the pottery.
Solution: Inadequate pottery cleaning or the use of a glaze that is inappropriate for the type of clay can both contribute to this problem. Make sure the pottery is spotless and clear of any contaminants or oils before glazing to prevent this. A glaze that is appropriate for your clay and firing temperature should also be used.

In conclusion, there are many issues that can arise when firing pottery with glaze, but with the right planning, skill, and problem-solving, potters can produce stunning and robust finished products. Just practice more. Easier said than done.

Is It Possible To Glaze Unfired Clay With Non-Toxic Clear Glazes?

Unfired clay can be glazed with non-toxic transparent glazes. It is crucial to remember that not all glazes—not even those that are clear—are non-toxic. Some glazes might contain substances that are toxic if consumed or inhaled, or that, when fired, emit toxic fumes.

Before purchasing and using the glaze, make sure to thoroughly read the label or product information if you want to use non-toxic clear glazes. Look for glazes that are formulated especially for use on pottery or ceramics, are designated as non-toxic or food-safe, and are both. There are many non-toxic clear glazes on the market, and when applied correctly, they can create stunning and long-lasting results.

It is also essential to note that when working with pottery and ceramics, even with non-toxic glazes, it is crucial to use the right safety gear and techniques. When handling glazes and firing pottery, put on a respirator helmet, gloves, and other necessary safety tools. Observe all safety instructions given by the oven and glaze manufacturers.

How Can I Achieve A Gloss Finish On An Unfired Pot?

A glaze that is designed to create a glossy surface can be used to give an unfired pot a gloss finish. The “general” stages are as follows:

  1. When selecting a clear glaze, look for one that will result in a glossy surface. To make sure the glaze is compatible with the kind of clay you’re using and that it can be fired at the temperature of your kiln, closely read the label or product information.
  2. Apply the glaze: Apply the glaze to the unfired vessel using a brush or another applicator. Aim to evenly cover the complete surface, leaving no gaps or particularly thick regions. To accomplish the desired thickness, you might need to apply several coats of glaze, depending on the glaze.
  3. Before firing the pot, allow the glaze to fully dry. The drying time can change based on the temperature and humidity of your workplace.
  4. To guarantee that the pot is fired to the proper temperature and for the proper amount of time, follow the firing instructions included with your glaze. When firing your pot, make sure to use the right firing sequence and the right safety gear.
  5. After the firing is finished, gently remove the pot from the kiln and allow it to cool to room temperature.
  6. Examine the finish to make sure that the glaze has created a glossy finish after the pot has cooled. Check the firing cycle and think about adding more glaze and firing the pot again if the finish is not glossy.

Are There Any Specific Stroke & Coats Techniques That Work Well For Glazing Unfired Clay?

On bisque-fired or unfired clay, the underglaze brand Stroke & Coat can also be applied as a glaze. The following Stroke & Coat procedures are effective for painting unfired clay:

  1. Thickening the glaze. Stroke & Coat can be made into a wash and added to unfired clay by dilution with water. A more even surface is produced by thinning the glaze, which enables it to absorb into the clay. To make a thin wash, combine the glaze and water in a 1:1 mixture.
  2. Using a sprayer to apply the glaze. Stroke & Coat can be applied with a sprayer to produce a uniform, smooth coating of glaze. Apply the glaze in a series of even, thin coats using an airbrush or spray container.
  3. Applying the glaze with a sponge. Stroke & Coat glaze can be applied with a sponge to produce a textured surface that is perfect for decorative items. Apply the glaze in a stippling motion with a wet sponge to produce a surface with a marginally raised texture.
  4. Different colors can be layered to make a multicolored, textured surface with Stroke & Coat glazes. After applying the first glaze layer and allowing it to dry, add a second layer in a different hue. A textured, multicolored surface is produced by removing some of the second coat of glaze with a damp sponge.
  5. Using cutouts to make patterns. When using Stroke & Coat glazes, use stencils to make patterns or designs. Place the pattern on the unfired clay, and then use a brush or sponge to apply the glaze. To see the design, remove the stencil.

A few methods that work well with Stroke & Coat glazes on unfired clay include these. The secret is to try out various methods and identify the ones that are most effective for the specific job you are working on. Always adhere to the manufacturer’s instructions for Stroke & Coat glazes and try your methods on a small patch of clay before applying the glaze to the entire object.

What Is The Two-Step Firing Process?

To lessen the possibility of fractures and warping in the final product, a two-step firing procedure can be used when working with unfired clay. A bisque firing and a glaze firing make up the two firing steps of the two-step firing procedure.

First firing is a bisque firing, which is carried out at a lower temperature than the glaze firing. In order to make the clay hard and porous enough to receive glaze, the bisque firing is used to completely remove all of the water and organic material. Depending on the type of clay used, bisque firing is usually performed at temperatures between 1800°F and 2000°F. The object can be polished or sanded to remove any blemishes or rough edges after the bisque firing, which leaves it hard and brittle.

Glaze firing. Following the bisque firing, a glaze firing is conducted at a higher temperature. In order for the glaze to attach to the clay and create a surface that resembles glass, it must be melted during the glaze firing. Depending on the type of glaze used, glaze firing usually takes place at a temperature between 2100°F and 2400°F. Depending on the size and thickness of the object, the glaze firing could take several hours.

The clay is given a chance to dry out, turn firm, and become porous through the use of a two-step firing procedure before the glaze is applied. By doing this, the chance of the clay cracking or warping during firing is decreased, which can happen if the glaze is applied to clay that is moist or damp. Furthermore, firing the clay at a lower temperature for the bisque firing and then firing it at a higher temperature for the glaze firing gives the artist greater control over the piece’s end appearance. Glazed bisque-fired pottery can also be made using this method.

The type of clay and glaze being used, as well as the size and thickness of the piece, can all affect the precise firing temperatures and times, it’s essential to remember. To guarantee a successful firing procedure, it is crucial to adhere to the manufacturer’s recommendations for the clay and glaze.

What Are The Advantages Of Firing Twice?

In comparison to a single firing process, the two-step firing process has a number of benefits. The following are some of the major benefits that I see:

  1. Reducing the probability of cracking and warping in the finished piece is made possible by the two-step firing process. There is less moisture in the clay that might cause it to fracture or warp during the firing process if it is allowed to dry out and become firm and porous before the glaze is applied.
  2. Improved adhesion of the glaze. The bisque firing helps to make the clay’s surface more porous, which makes it easier for the glaze to attach to it. This results in a glaze that is stronger and lasts longer.
  3. Greater control over the outcome. Potters have more control over the outcome of the piece when they use a two-step firing procedure. To produce a smooth and even surface, they can make adjustments after the bisque firing by sanding or polishing. Additionally, they have the ability to apply the glaze more precisely and uniformly, which could result in a result that is more constant and appealing.
  4. Ability to use a broader range of glazes thanks to the two-step firing process. A two-step firing procedure allows potters to fire the bisque at a lower temperature and then apply a higher temperature glaze during the second firing. Some glazes require a higher firing temperature than the clay can withstand.

Overall, firing pottery in two steps is a tried-and-true technique with many benefits. It enables potters to produce items of excellent quality with a surface that is more resilient and long-lasting. All my work that I sell is fired twice.

Helpful Techniques You Can Employ When Glaze Firing

When firing glazed unfired clay, there are a few extra techniques that may be useful. Here are my top tips:

  1. Pre-heat the kiln. Pre-heating the kiln can help the pieces dry more gradually and uniformly during the firing process when you are loading your glazed unfired pieces into the kiln. This can lessen the possibility of splitting or warping in the final products.
  2. Use kiln shelves and stilts. It’s crucial to use kiln shelves and stilts when putting glazed unfired pieces into the kiln to help support the pieces and prevent them from sticking to the kiln shelf or other items. Typically, high-temperature materials like cordierite or silicon carbide are used to make kiln shelves and supports.
  3. To prevent the buildup of dangerous fumes or gases, it is crucial to allow for adequate ventilation during the firing procedure. This can be accomplished by holding the lid open slightly or opening the kiln’s vent slightly. Or leave the peepholes open during firing to let the moisture escape.
  4. Keep a careful eye on the firing process to make sure the pieces are firing evenly and aren’t having any problems, like cracking or warping. This is particularly important during the ramp-up to the glaze firing temperature.
  5. Take into account a soak period. After the kiln achieves the glaze firing temperature, it can be beneficial to leave the pieces there to soak for a while, say for 10-15 minutes. This can aid in the glaze melting completely and fusing to the clay, giving the surface a more robust and long-lasting finish.

Conclusion And Summary

What do you get when you mix a potter with a musician? Purple Glaze!

Jimi Hendrix was more than just a guitar player.

When firing pottery to glaze, it’s important to consider the following:

  1. Pick the proper glaze. Decide on a glaze that is suitable for the type of clay and the firing temperature you’re using. Take into account the glaze’s intended color, finish, and texture.
  2. Apply the glaze correctly by spreading it out evenly and using the suggested layer thickness. Before putting on the glaze, make sure the piece’s surface is dust- and debris-free.
  3. Before firing the piece, allow the glaze to fully dry. The glaze won’t run or bubble during firing as a result.
  4. The object should be bisque fired at a temperature suitable for the type of clay you are using. This will make a surface that is permeable and allow the glaze to stick.
  5. The piece should be fired with glaze according to the suggested temperature and holding period for the glaze you’re using. To make sure the piece is firing evenly and faultlessly, keep a careful eye on the firing process.
  6. Allow the piece to cool down. To avoid thermal shock, let the piece cool gradually in the kiln after the firing procedure is finished.
  7. Analyze the final product. Make sure the glaze has been applied correctly and inspect the finished piece for any flaws or problems.

When discussing the possibility of glazing unfired clay, it is essential to consider the type of clay being used, such as greenware pottery or leather hard clay. Common techniques for applying a transparent coat to pottery include dipping pottery in glaze, using a detailer bottle, or employing special tools. These methods can produce a beautiful translucent finish on your greenware piece.

However, glazing unfired clay may impact neighboring pieces during the process. Utilizing a shelf cone (support for kiln shelf) can help separate and protect the pieces, while maintaining a cohesive process. Mayco Stroke & Coat is a popular choice for achieving opaque coverage, transforming the appearance of dried mud into a stunning work of art.

Spray Glazing is an alternative method that allows for even application on the whole piece. Combined with Crystalites, this technique can create breathtaking Pottery Cascades, offering an exquisite visual effect. No matter which method you choose, it is crucial to follow proper procedures and ensure that the air-dry clay is ready for the glazing process.


References

“Mastering Cone 6 Glazes: Improving Durability, Fit and Aesthetics” by John Hesselberth and Ron Roy – This book is a comprehensive guide to glaze firing at cone 6, covering topics such as glaze formulation, firing schedules, and troubleshooting.

“The Glaze Book: A Visual Catalogue of Decorative Ceramic Glazes” by Stephen Murfitt – This book is a comprehensive visual guide to a wide range of glazes, including recipes, firing schedules, and techniques for achieving different effects.

“Electric Kiln Ceramics: A Guide to Clays, Glazes, and Electric Kilns” by Richard Zakin – This book covers all aspects of electric kiln firing, including glaze formulation and application, as well as firing schedules and troubleshooting.