Tessera material comes in varying thicknesses. Stained glass is about 1/8-inch thick, vitreous glass tiles are 3/16-inch thick, smalti can be as much as 1/4-inch thick, and marble gems are about 1/2-inch thick. The 1/16-inch difference between vitreous glass tiles and stained glass doesn't sound like much, but in the context of mosaics, it's significant.
Early in my mosaic life, I made the mistake of indiscriminately mixing vitreous glass tesserae with stained glass tesserae. I thought I'd creatively combine the two types to give my work texture, depth, and a sense of perspective. I spent two months carefully cutting and gluing each tessera piece. Finally, I finished. It looked wonderful. Time to grout. I mixed a batch, slopped a big pile in the middle, and spread it with my float. Good grief, what a nightmare. The float wouldn't squeeze grout into all the joints because the thicker vitreous tesserae stuck up too high. No matter what direction I spread, the vitreous tesserae prevented me from squeezing grout into all the spaces. Additionally, grout built up too high in the joints between the vitreous and stained glass tesserae. Sweat beaded on my forehead dripping all over my mosaic as thoughts flew in my head, "Oh, no, what have I done? All that work and now it's ruined!" I scrambled using the float, paper towels, and old rags to fill the joints and wipe away excess grout before it set. Success at last (whew!). Finally, I had uniformly filled all the joints and wiped away the excess. The final product looked okay, but it didn't turn out as well as I had hoped. Also, I destroyed my favorite grout float, which added to my disappointment. The float's rubber bottom ripped to shreds from running it over the sharp points and edges of tesserae that stuck up higher than others. Good grief.
If you're a mosaic novice, I suggest using tesserae of similar thickness for your first few projects. However, that doesn't mean you absolutely cannot incorporate varying thicknesses into your work. Texture can create beautiful effects. For example, you may want to design your mosaic wall hanging with vitreous glass for the border and stained glass for everything else. In this case, ensure the grout joints between the thicker vitreous glass and the thinner stained glass are a bit wider than normal so the grout can properly slope downward without covering the stained glass. Although grouting spaces between the vitreous and stained glass tesserae requires extra care, it can, indeed, look great.
When selecting tessera types, be aware that varying thicknesses require extra care and work when grouting. Also, it's important to plan your project well to know if varying thicknesses are appropriate. For example, suppose your mosaic tabletop or trivet requires a flat surface. As a novice, it's easier to get a flat surface using tesserae of the same thickness.
Bill Enslen has created lovely mosaic art for 30 years. His new eBook, Mosaic Pieces: Essentials for Beginner and Professional Mosaic Artists, gives you step-by-step details for creating your own mosaic masterpieces. Visit his website and read the free sample chapters at Glass Mosaic Tile Art. Let him show you just how easy it is. With Bill's help, you can do it. Yes, you can!
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