02
Dec

underglazing

I picked up some really cool underglazes recently. These are the Amaco Semi-Moist Underglazes¬† (“SMUG”) and they go on like watercolour paint. I experimented on some porcelain and the colour on the leather clay before firing was the exact colour after bisque. Spot on. I’m completely amazed because this is a thing that never ever happens in ceramics in my experience. The colour that goes on is usually not even remotely related to what you end up with. Here’s an example of a pot before and after glazing. This is what it looks like just before going into the kiln, and just after it comes out to show that really, a potter has not a clue what it will look like until it’s all said and done. Glazing is my least favourite phase in ceramics because a few minutes applying glaze incorrectly can leave a piece unusable or… just plain ugly :   Not only do the glazes look different before and after firing, layering glazes changes them drastically and a potter cannot rely on the basics of paint colour theory to give them any idea what will happen. Blue + Yellow does not equal green in mid to high fire ceramics. In the kiln, glazes with usually copper or barium in the presence of oxygen = green end colour. To make things a little more interesting, the sequence in which you layer different glazes also matters to the end result. In this example from Mayco, the technician layered two glazes on the plate, first dipping one side and then rotating the plate to dip the other glaze to overlap the first. On the first plate, she dipped the red first, then dipped the blue overlapping. In the second photo, she dipped the blue onto the plate first, then dipped the red overlapping. Note the crazy crystals that formed when the blue was put over the red and the different result from layering in a different sequence. Glazing, she be an exercise in practice, requiring detailed notations on exactly how and in what order the glazes were brushed or dipped. Because I want to be able to reproduce results if they turn out really inspiring, I take incredibly detailed notes when glazing. Now these underglazes are making my heart flutter. The blue, yellow, green, purple and oranges on my test piece made it through green to bisque without a hint of change. Now that I’m turning up the heat 250 degrees C to 1240 C for a cone 6 glaze firing and I’m very eager to see how they do. Between my black underglaze pencil and the SMUGs, the effects that I’m getting are ones I’ve always dreamed of achieving in ceramics.¬† I’m drawn to charcoal shading and dark lines, light accents of variegated colour and a vast sea of negative space to frame designs. My challenge has been that I want mid to high fire ceramics because of longevity of the end product (they don’t call it stoneware for nothing). However, in the highter temps, colours run or subtle colours “burn off”, disappearing as the temp rises in the kiln, never to return. I wanted something simple in design, lightly tinted with colour with a feeling of watercolour paint on this sample set of mugs. I used the underglazes and underglaze pencil to echo an earlier design I’d etched into tea cups. I’m very pleased. I love Ceramics Canada for being able to order the SMUGs for me so I could avoid a $23 shipping fee. Cross your fingers that these mugs look exactly the same once they arise from the glaze firing. I’m more than a little enamoured with the design.