How Do You Seal A Clay Oil Lamp?

Clay oil lamps have been used for thousands of years to provide portable illumination. Often made from terra-cotta or earthenware, these lamps consist of a fuel chamber or reservoir that holds oil or grease, and a wick which is lit to produce light.

Sealing a clay oil lamp serves several important purposes. First, it helps make the lamp watertight so oil does not leak out. Second, sealing the lamp helps protect the surface from staining and absorption of oils or smoke. Third, sealing provides an impervious barrier so the lamp can be safely cleaned without damaging the clay. Finally, a good seal locks in designs, glazes, or paints applied to the lamp exterior.

There are a few common techniques for sealing clay lamps. The lamp can be coated with a liquid clay slip, which is allowed to dry and then fired in a kiln. This vitrifies the slip into a glassy coating. Another option is to apply wax by dipping or brushing. Plant-based waxes melt at low temperatures, allowing the wax to fully penetrate the clay surface. Finally, modern sealers like polyurethane can be brushed on in thin coats. Each method has advantages and disadvantages in terms of accessibility, durability, and aesthetic result.

Materials Needed

The main material you’ll need for sealing a clay oil lamp is clay. Choose a clay that is free of contaminants and suitable for high temperatures, like stoneware or porcelain. You’ll also need to make a slip, which is a mixture of clay and water. Opt for a clay slip that matches or complements the color of your lamp.

In addition, you’ll need paints and glazes to decorate the lamp. Look for glazes rated for the temperature your kiln can reach. Brushes will be useful for applying the slip and paints. Finally, have containers on hand for mixing up your slip and glaze mixtures.

Making the Slip

The slip is one of the most important ingredients for sealing a clay oil lamp. Here is a simple recipe to make an effective homemade slip:

You’ll need:

• 1 cup clay
• 1/2 cup water
• 1 teaspoon vinegar
• 1/2 teaspoon table salt

Start by crushing the clay into a fine powder using a mortar and pestle or something heavy like a rolling pin. Make sure there are no large chunks left.

In a bowl, mix together the crushed clay, water, vinegar and salt. Stir vigorously until fully combined into a smooth, liquid clay slip. Allow to sit for 10 minutes so ingredients fully incorporate.

The slip is now ready to apply to the lamp for sealing.

Applying the Slip

Applying a slip layer is an important step in sealing a clay lamp. There are two main methods for applying slip: brushing it on or dipping the lamp.

Brushing the slip on with a soft brush allows you to completely coat the lamp’s surface while avoiding drips or uneven coverage. Use long, smooth strokes and ensure you don’t miss any cracks or crevices. Let each layer dry completely before adding another coat.

The dipping method involves submerging the entire lamp in a container of prepared slip. This ensures uniform coverage in a single step. Gently lift the lamp out, allowing any excess slip to drip back into the container. Be careful not to leave any drips along the bottom edge.

Regardless of application method, the goal is to fully seal the clay surface with slip. Aim for at least 2-3 thin, even layers and allow each coat to dry for a few hours before adding the next. Uneven or thick application can lead to cracking when the lamp is fired. Once the final layer is dry, the lamp is ready for additional decorative layers like paint or glaze.

Adding Paints and Glazes

There are several types of paints and glazes that can be used to decorate a clay oil lamp. The main options are:

Acrylic Paints – These are water-based paints that come in many vivid colors. Acrylics work well on bisqueware and can be used to hand paint designs before firing the lamp. They are inexpensive, easy to apply, and clean up with water.

Ceramic Glazes – Glazes provide a glossy, glass-like coating over the clay body. They come in various colors and effects. Glazes must be fired on the lamp in a kiln to harden them into a permanent finish. Using glazes allows more color options than just painting.

Underglazes – These special ceramics paints are applied to greenware or bisque before glazing. The colors become permanent when fired under a glaze. Underglazes allow for hand painting intricate designs.

When adding paints or glazes, it’s important to apply them evenly in thin layers using soft paintbrushes. Dabbing in a stippling motion works better than brushing back and forth. Uneven application can lead to cracking or peeling. Allow each layer to dry fully before adding another. Use light coats to build up the color gradually.

Firing the Lamp

Firing is one of the most important steps in sealing and finishing your clay lamp. You have two main options for firing: kiln firing or pit firing.

Kiln firing involves placing your lamp in an electric or gas-fired kiln that allows precise control over temperature. Kilns allow climbing to a specific target temperature, holding at that heat, and then cooling gradually. For an oil lamp, aim for a final kiln temperature of cone 04-06 which equates to approximately 1915-2120°F (1046-1163°C). Soak at the target temperature for 10-20 minutes.

Pit firing involves placing your lamp in a fire pit or barbecue grill. This method lacks the precision of a kiln, but can reach similar temperatures. Build a fire around or below your lamp using kindling and firewood. Maintain the fire for 1-2 hours, feeding more wood as needed, then let cool overnight before removing your lamp.

Regardless of method, firing should thoroughly and evenly heat the clay to its maturation point to vitrify the clay and create a impermeable lamp that holds oil. Firing for too short of a time risks under-firing and weak sealing. Over-firing can damage the clay. Test to ensure proper firing before applying finishes.

Sealing the Wick Hole

One of the most important steps in finishing a clay oil lamp is properly sealing the wick hole to prevent oil leaks. This can be done using more clay slip or a special clay putty.

Start by letting your completed, fired lamp fully dry. Ensure no moisture remains inside the wick hole or on the surface surrounding it. Then prepare some extra clay slip using the same recipe you used earlier in the lamp making process. Alternatively, you can purchase a commercial clay putty made specifically for sealing up holes and gaps in clay objects.

Use a small spatula or knife to press the slip or putty into the wick hole, packing it in tightly to fill the space fully. Apply enough to create a raised mound over the hole. Then use a damp sponge or your finger to smooth out the slip/putty until it is even with the surrounding surface.

Allow the lamp to dry fully again before proceeding. The sealing material will shrink slightly while drying. Check that the wick hole remains completely filled with no cracks or gaps. If needed, apply a second coat of slip or putty to trouble spots.

With the wick hole sealed properly, you can add oil and a wick without worrying about messy leaks.

Polishing

Once the clay lamp has been fired, it’s time to polish and smooth the surface for an attractive sheen. Start by sanding the lamp with increasingly finer grit sandpaper, starting with a coarse grit like 60 and working up to at least 600 grit. Be sure to sand in small circular motions to round edges and smooth facets. Pay close attention to intricate carved details and ensure all surfaces are evenly sanded.

After sanding is complete, it’s time to buff the lamp. Use a soft polishing wheel or cloth with a polishing compound to give the final buffed shine. Apply the compound and hold the polishing wheel to the surface, again using small circular motions. Overlap passes and work over all surfaces multiple times to achieve an even glossy sheen. Be careful on intricate areas and details. When complete, wash off any remaining polishing compound with water and a soft cloth. The lamp is now smoothly sanded and buffed to a beautiful polished finish.

Waterproofing

Once your clay lamp is fired, painted, and finished, you’ll want to waterproof it before use. This seals the porous clay and prevents moisture from compromising the integrity of the lamp.

There are a couple options for clear coats to waterproof the lamp:

• Polyurethane – This is a common clear coat that provides a good protective barrier. Use an oil-based polyurethane for best results.
• Resin – Epoxy and UV-cured resins also work well. Make sure to get one formulated for glazed ceramics.

For application, you can either brush on the clear coat or dip the lamp. Dipping ensures the entire piece gets an even coating, while brushing allows you more control.

To dip, fully submerge your lamp in the clear coat and let it soak for a few minutes. Lift out gently at an angle to allow excess to drip off. Lay the lamp on its side to dry completely before recoating or using.

For brushing, use a soft brush to coat the entire lamp surface. Apply in thin layers and let dry fully between coats. 2-3 coats is usually sufficient for good protection.

Once sealed, your clay oil lamp will be protected from moisture and ready for many years of use.

Caring for the Finished Lamp

Once your clay oil lamp is complete, you’ll want to make sure you care for it properly so it lasts for years to come. Here are some tips for caring for your finished lamp:

Handling Carefully – Clay, even when fired, is breakable. Be sure to pick up and move your finished lamp with both hands. Don’t apply too much pressure at any one point, as this can cause cracks or chips in the clay body.

Dusting and Cleaning – Over time, dust and dirt can build up on your lamp. Use a soft cloth to gently wipe down the outside surfaces of your lamp periodically. Avoid abrasive cleaners or scrubbing, as this can remove any painted designs. If needed, a slightly damp cloth can help remove more stubborn dirt.

Storing Properly – When not in use, find a safe place to store your clay lamp, such as on a sturdy shelf or inside a cabinet. Wrap your lamp in tissue paper or place it inside a box to prevent dust buildup. Avoid exposing your lamp to extreme temperatures or moisture.