Iron oxide powder can be used to apply colour to ceramics, creating shades of red, black and yellow, as well as many colours in between, depending on the firing temperature. You can combine application techniques to create varied and unique designs and patterns for your creations using some basic steps for applying iron oxide to your ceramics.
Iron oxide glaze mix
Measure out the glaze and add oxide powder accordingly. For example, 125 ml (1/2 cup) glaze would need 1 ml (1/4 tsp) iron oxide powder.
Brush the glaze onto the fired ceramic surface.
Allow each coat to dry before applying the next. Apply two to three coats, depending on the thickness of the glaze. Smooth out imperfections in the glaze surface with your fingers before applying the next coat.
Allow the glaze to dry before firing in the kiln.
Iron oxide slip mix
Mix iron oxide powder into liquid slip. Start with a very small amount, such as a 1 ml (1/4 tsp), then gradually add more powder, if needed, to achieve the desired colour depth.
Apply slip to a moist clay surface. There are several methods of applying slip, including trailing, marbling, feathering and painting.
Allow the slip to dry gradually. Drying time will vary depending on the slip's thickness.
Coat the slip with glaze when it is completely dry, then fire in the kiln.
Under glaze application
Mix iron oxide powder with water until it is the consistency of watercolour paint -- slightly transparent when spread on a surface.
Apply oxide mixture to the fired ceramic surface, using a brush or piece of foam. Dab or stroke the iron oxide "paint" in the desired design.
Allow the "paint" to dry completely before applying the glaze. Or, if you want the paint to run into the glaze, apply the glaze when the paint is still wet.
After glazing is complete, fire the ceramic as usual.
Titanium and rutile can provide beautiful variegated colours to your ceramics when mixed with iron oxide.
Firing temperature greatly determines iron oxide's end-product colour.
Note that 28 g (1 oz) of glaze covers approximately 194 square cm (30 square inches).
Most glazes require three coats for complete coverage, whether you are using opaque or semi-transparent glaze. Heavy glazes may only need two coats.
Most glaze manufacturers formulate their glazes for cone 04 bisque and fired to cone 06.
Zinc oxides often do not provide good colours when mixed with iron oxides.
Many oxides and carbonates are toxic. Wear masks and gloves when handling them. Avoid getting oxides in the eyes, nose, or mouth.
Kilns are best kept outside or in a separate, closed-off room, with adequate ventilation.
Ceramics that are improperly dried or glazed can explode during firing.