Basics of Ceramic Glazing: Types & Techniques

Hello and welcome back to Clay Corner Studio's online classes. In this video, you will be introduced to different techniques of glazing that you can apply to your own ceramic projects. Before a ceramic piece is glazed, it's not considered food safe and not always functional because it's usually still porous and can absorb water. Glaze is therefore applied to seal the ceramic body and make it waterproof. You can think of glaze as a thin layer of glass that coats your ceramic piece that makes it stronger and more attractive. Glazes can come in a variety of colors, textures, and finishes that can be applied to ceramic bisqueware to achieve different results and effects. Some are high-fired and others are low-fired. Low-fired glazes are typically more vibrant and are great to use for beginners since they tend to be more affordable. Underglazes are a little different from your usual glazes because their base is made from clay slip and pigment which does not form a layer of glass when fired which also means that they can still absorb water. Underglazes are usually sealed with a clear glaze which is what you see here on the top half of the tile. The cool thing about underglazes is that unlike glazes, they can be applied to both fired bisqueware and greenware or unfired clay alike. When you have a bunch of different glazes in your studio, it's a good idea to create numbered test tiles to help you keep track of them. You can think of this as a physical catalog of your glazes. This allows you to easily refer back to them and see how they behave on certain clay bodies or textures when deciding which glazes to use for your future projects. Mid- to high-fired glazes tend to come in a wider range of textures, finishes, and effects and also look more sophisticated. Take for example this matte chino glaze which has an earthy finish or this glossy mid-fired glaze which breaks into several different colors when applied on texture. Of course, some glazes can look completely different and behave in different ways when applied on different clay bodies so it's always a good idea to create test tiles for all combinations of glazes and clays that you have available in your studio. There are many different ways to apply glazes to achieve different creative results. They can be layered, sprayed, textured, or painted on depending on whether you're going for a solid color, a painted scene, or an abstract look. Remember that glazes can only be applied to bisqueware which has been fired to cone 04. Before glazing, it's very important to clean the piece very thoroughly from any dust or particles that might be on it. To do that, you can simply use a sponge and clean water to wipe it. The face planter I'm using here was made for one of our slab building online classes. If you're interested in learning how to make your own, please check our other available class bundles. Once you've cleaned your piece, you can go ahead and prepare the rest of your materials. For brush-on glazes, it's best to use soft brushes such as hake, watercolor, mop, or fan brushes. You'll also need a cup of water to wash your brushes in and a sponge for any cleanup. And it's a good idea to have a hand towel to dry your brushes after washing them. We're first going to start with a black glaze liner to paint the eyes. Always shake your glaze bottles very well before using them. It's also a good idea to run a test line of your glaze before applying it on your piece. As you can see, I'm applying the liner glaze on the eyelashes and mouth of the face. Although the lines don't look very neat at the moment, I will then use a wet sponge to wipe off the excess glaze. And that way, I can have clean lines of glaze that remained in the debossed areas only. You can apply this same technique to any other texture on your piece, which you'll see later on in this video. Next, I'm using some underglaze to apply a pink blush. Brush-on glazes and underglazes must usually be applied in three coats to achieve the best results. However, some might require more or less than that, so always check your bottle to see what's recommended. I'm only applying two layers here because I want my blush color to be a little translucent instead of solid. Next, I'm taking a brown liner to apply some freckles. Once that's done, I'm taking a yellow earthenware glaze, which is low-fired, and brushing it onto the bottom half of the planter. This is the basic technique of brush-on glaze that you can apply to any other piece. Notice how I'm not spreading my glaze too thinly, and I'm frequently reloading my brush with more glaze. Avoid using too many strokes when applying your glaze, because they can sometimes show up after firing and create uneven patches of color on your piece. I'll apply three coats of glaze, allowing each coat to dry completely before applying the next, which usually takes a few minutes. Notice how I'm leaving the base of the feet free of glaze. The reason for that is because glaze melts in the kiln and adheres to any surface it's in contact with. If we were to apply glaze to the base of the ceramic object, that will make it stick to the kiln shelf, which would ruin both the piece and the shelf. So always make sure to clean the base before firing. Once I'm done glazing the bottom half, I can go ahead and clear glaze the top half and inside of my planter. This will seal the underglaze I had applied earlier and leave the rest of the areas white, since my clay body is white, and give it an overall glossy coating. To make it easier for me to track how many coats I've applied, I can draw a line on my working surface once I'm done with each layer. When brushing on glaze, always try to apply it in a unified direction instead of doing random strokes to ensure an even coat and color throughout the piece. Keep in mind that all glazes you use on a single piece must be compatible with the same firing range of the clay body you're using. In other words, here I'm using only low-fired glazes, which are compatible with each other. The clay I used to build this piece is also earthenware clay, which also means that it's low-fired. Once it's dry, I can now fire my piece at cone 05, and this is how it looks after firing. Another fun glazing technique you can use is stenciling, which I will apply on this simple lidded jar also available as a tutorial in our slab building online classes bundle. Just like before, we first need to thoroughly clean our bisque with a wet sponge before glazing it. Next, if you don't have any stencil sticker templates, you can simply use some masking tape and cut your designs out of it. I will begin by wrapping the tape around the middle of my jar, making sure that it's nice and smooth and not wrinkly. With the aid of my banding wheel and a measuring tape, I'm drawing a zigzag pattern, which I will then cut out with an exacto knife. I will then go ahead and tape the rest of the exposed area on my piece to cover it from any splashing or dripping glaze. To create a sprayed or splatter effect, you can use a bristle brush or even a toothbrush to spray the underglaze by tapping it or flicking finger or a wooden tool through it. This can create a bit of a mess, so it's best to clear up your workspace before doing this. Spray as much glaze as you need to achieve your desired effect, and once you're done, allow the glaze to dry before removing the tape. I will then clear glaze this jar using dipping glaze, but before I do that, I will apply some wax resist to the base of the jar using a brush, which will repel the glaze while dipping the piece in it. One thin coat of this is enough, and the wax will burn off in the can, leaving the base clear. I'll also apply some wax resist to the bottom edge of the rim on the lid. Dipping glazes usually come in dry form, and they must be mixed with water. The tool you see here is called dipping tongs, which lets you hold your piece as you're dipping it in the glaze while covering minimal surface area. When dip glazing, you want to submerge your piece in a smooth motion, not too quickly, not too slowly. You also need to make sure that the inside doesn't trap any air pockets as you're submerging it, so it's a good idea to dunk it on the side and tilting it upright as you reach the bottom, and then reversing that motion as you take it out to allow the extra glaze to pour out. Once I set it down, I can use my finger to pick up some glaze and patch up the scars left behind by the tongs. It differs from glaze to glaze, but you normally want to dip your piece for approximately 3 to 5 seconds. You only need to dip once if you're applying a single glaze. I will then use a wet sponge to remove any excess glaze droplets on the base. After firing, this is how the jar looks like. Using the stenciling and spraying techniques. When it comes to glazing the contour lines of a textured imprint, such as this mug with pressed-leaf imprints, it's a good idea to first sand down any unwanted texture and smooth down the plain surfaces by using sanding paper. Once sanded, your piece will be very dusty, so make sure to clean it very, very thoroughly and rinse your sponge frequently in clean water to avoid spreading the dust even more. Next, I'm keeping the textiles of my chosen colors next to me to remember the different combinations I'm going for. For this technique, it's best to use underglaze, since it can be layered or mixed together. And because I'm only coloring sections of the piece, which means that I can then clear glaze the rest of the blank areas on the mug. As you can see, I'm not being too careful around the edges of the leaf shape, because these will be cleaned up in the next step. I'm also making sure to apply three layers of underglaze. Here, I'm layering two different colors together, lime green and pink, to create a gradient effect. The nice thing about underglazes is that you can treat them in a very similar way as you do paint, which is unlike other glazes. I'm making sure to apply three coats of each color that I'm using, so three coats of green and three coats of pink. Here, you can see that I'm mixing orange and red underglazes together to create a coral color, which is also a perk of working with underglazes. Keep in mind that the deeper the texture, the more color it catches. Once the underglaze has dried, I can then clean up the edges using a wet sponge. As you're wiping off the excess underglaze, make sure to wipe into the design instead of out towards the blank surface to avoid staining it. It's also very important not to rub and to continuously flip your sponge around and to wash it off as frequently as you can. Once done, I can go ahead and clear glaze my mug using the same brush on or dipping techniques shown earlier. And this is how it looks like after firing. The final technique we'd like to share with you is called Sgraffito, which is exclusive to underglazes only. What makes this technique special is that it's usually done directly on unfired clay. It's best to work with leather-hard clay for this one. First, apply three coats of underglaze to your clay. Once that's dry, you can use a variety of different tools such as ribbon tools, carving tools, or pin tools to carve out your designs on the clay. What you get is a negative effect that shows the color of the clay beneath the underglaze. This works great for detail or pattern work. Once fired and clear glazed, this is how it looks like. You can also combine this technique with any of the other techniques mentioned earlier to create even more interesting effects. We hope that you found this video informative and helpful. Please be sure to check out our other online class bundles to learn more about how to create fun ceramic projects.