What Is Raku Firing And How Does It Work?

What is Raku Firing?

Raku firing is an ancient Japanese ceramics technique that has been used for many centuries to create a very unique finish to wares. The Raku technique dates back to the 16th century, traditionally crafted by hand and not thrown on a potter's wheel.

The Raku technique is essentially when glazed ceramics are taken from the kiln while they are still glowing red hot and are then placed in a material that would be able to catch fire, such as sawdust or newspaper. This technique is used to starve the piece of oxygen, which creates a myriad of colors within the glaze. Raku firing without glaze on them means that the oxygen is taken from the clay itself rather than a glaze, which results in some areas having a matte black coloring. 

Raku firing creates completely unique pieces as there is never a certainty as to how the final piece will turn out. Raku essentially creates a unique design every time, so there is less control on the outcome.

How does Raku firing work?

Raku firing is much quicker than normal firing, taking around 1-2 hours in comparison to regular firing which can take up to 24 hours. The first process is to glaze your ware using a specialist Raku glaze, which can be found at some craft shops and pottery equipment wholesalers. These glazes are specially made to have a low melting point so they will melt at cone 06 in about an hour. A thin layer of the glaze is better for the Raku technique to have an effect and a quicker melting point.

The next step is to load the kiln with your wares and bring the temperature up to 1850 degrees fahrenheit, which should take about an hour. To ensure that the process is working out correctly, check on the ware every 15 minutes or so after 45 minutes of firing. If your glaze is starting to bubble then the process is working! Once you notice the glaze bubbling, leave the ware for another 15 minutes before moving on to the next stage.

The point at which you remove your ware from the kiln is when it is glowing red and the glaze surface appears shiny and liquid. While you're waiting for the kiln process, you need to prepare your vessel for reducing the oxygen to the piece. Shredded newspaper or sawdust should be added to a metal dustbin or similar. The vessels should only be a little bigger than the ware you are putting in them. The tighter the area around the ware, the better the reduction in oxygen, which creates a better color spectrum.

Once the pieces have achieved a red hot glow, you're going to need 3 people to do the Raku process. One person is needed to open the door of the kiln, one to pull the pieces out of the kiln with tongs and place them in the metal container, and one to close the lid on the metal vessel. Ensure to wear appropriate protection at this point as you are dealing with very hot ware. 

When the ware is removed from the kiln, the door should be closed between each piece being pulled out in order to retain the heat that is required. Place the pieces as quickly as possible into the waiting vessels to ensure that the heat is retained. Person 3 should wait for the newspaper or sawdust to catch fire, then quickly place the lid on the vessel to smoke the ware.

The next step is to wait a few minutes for the smoking of the pieces to take effect. Take care when the lid is taken away as the smoke will be hot and could cause facial burns if not done carefully. Additionally the wares are still extremely hot at this point, so removing them should be done with care. To cool the ware, you can pour some water onto them and then remove the pieces out with tongs and douse them in the bucket of water. At this point you should be able to see the effect that the technique has had on your finished ware.

How to glaze Raku Pottery

As a unique pottery method, glazing raku pottery requires specific skills and techniques. Here's a step-by-step guide on how to glaze Raku pottery:

Materials Needed:

• Bisque-fired Raku pottery pieces
• Raku glazes (formulated for the Raku firing process)
• Glaze brushes or tools
• Bucket of water for cleaning tools
• Glaze tongs or other suitable tools for handling hot pieces
• Protective gear (gloves, apron, and safety glasses)
• Combustible materials (sawdust, leaves, or newspaper)
• Raku kiln and propane tank
• Metal tongs for removing pieces from the kiln
• Fire-resistant containers for post-firing reduction

Procedure:

Prepare Your Workspace

Set up your work area with all the necessary materials. Ensure proper ventilation, and have a safe space for firing the Raku kiln.

Inspect Bisque-fired Pieces

Examine your bisque-fired pottery pieces for any imperfections. If needed, lightly sand any rough spots or edges.

Mix and Prepare Glazes

Stir the Raku glazes thoroughly to ensure an even consistency. Follow the manufacturer's instructions for mixing and application. Some artists prefer to thin glazes with water for specific effects.

Choose Glazing Technique

Decide on the glazing technique you want to use. Whether you're dipping, pouring, brushing, or employing resist techniques, each method will yield different results.

Apply Glaze

Use glaze brushes or tools to apply the glaze to your bisque-fired pottery pieces. Ensure an even and consistent application. Experiment with layering multiple glazes to create unique effects.

Add Resist Materials (Optional)

If you want to create specific patterns or leave areas unglazed, apply resist materials such as wax to those areas before glazing.

Allow Glaze to Dry

Let the glaze dry completely before firing. This is important to avoid any issues during the firing process.

Load Pieces into the Raku Kiln

Arrange your glazed pieces in the Raku kiln, leaving enough space between them to allow the heat and flames to interact with the glazes. Be mindful of the placement of combustible materials for the reduction process.

Raku Firing

Fire the kiln to approximately 1800°F (982°C). Monitor the temperature closely. Once the glazes have melted and the pottery pieces are red-hot, use tongs to quickly and carefully remove them from the kiln.

Reduction Process

Immediately place the hot pieces into a container filled with combustible materials (sawdust, leaves, or newspaper). The combustibles will ignite, and the container is then covered to create a reduction atmosphere. This step contributes to the unique surface effects of Raku pottery.

Cleaning and Sealing

After the reduction process, carefully remove the pieces from the container using metal tongs. Clean any remaining ash or soot, and if desired, apply a sealer to protect the finished surface.

What kilns are best to use for Raku firing?

There are a number of kilns available that are suited for the raku firing process. What needs to be considered is that the firing cycle of Raku is much faster than a typical firing and you need to make sure that you can get your kiln to a suitable temperature for this method. A good option for this is to use a pre-programmable electric kiln such as those offered by Soul Ceramics, whereby you can have a better control over the temperature and also be able to maintain that temperature for the requisite time. Our range of electric kilns can be found here.

In summary, Raku is a wonderfully experimental way of making unique designs and the fact that it has been used for centuries shows that it is still as popular as ever. The technique is relatively straightforward as long as the heat generated is at a high level and the glaze is suitably viscous to create the Raku effect.

Additional resources on pottery

• A guide to China painting
• How to fire pottery without a kiln
• The basics of glazing ceramics
• A mini guide to bisque firing