How to Do Glass Painting from a Pattern Tracing
If you want to do glass painting from a pattern tracing, first clean the glass with soap and water. Next, put the pattern you want to trace face down on the sheet of glass and tape it in place with masking tape. Then, flip the glass over, and wipe the area you'll be painting with rubbing alcohol so the paint has a clean surface to stick to. Using glass paint liner or dimensional glass paint, trace the outline of the pattern. Once you're done, give the paint enough time to dry, generally 6 to 8 hours. After it's dry, fill in the spaces with glass paint, painting all the way to the outline.
Gather your supplies. Glass painting requires a little more than just paint and brushes. You will also need to prepare your glass piece properly, so that the paint will stick. Some paints also need to be cured in an oven. Here is a list of what you will need to get a basic painting done: Glass object to paint Cotton balls Rubbing alcohol Design printed on paper Masking tape Glass paints Paint brushes Plate or palette Oven (optional) Find a glass piece to paint. You can paint things like jars, cups, or wine glasses. You can also paint a glass panel. The best place to get a glass panel is from a picture frame. When you are done painting, you can display the finished piece inside the frame. Make sure that the panel in the frame is glass, however; some frames come with an acrylic panel instead of glass. You can take the back out of a picture frame, or leave it in. If you decide to leave the back in, you might want to cover it with some white paper. Most glass paint is translucent, so it will show up best against a white background. Clean the glass with some soap and water. Even if the glass looks clean, you will still want to wash it. Any oil, dirt, or dust may keep the paint from sticking to the surface. Have your pattern or design ready. It needs to be printed on paper. If you are painting something like a cup or jar, the paper needs to be trimmed down so that it can fit inside. The best patterns to use are just outlines, like from a coloring book. Place the pattern where you want it to be. If you plan on using this glass piece for eating or drinking out of, move the pattern to a place where food, drink, or mouths won't be touching it. Even if a glass paint is labeled as "non-toxic," it may not be food-safe. If you are painting on a flat sheet of glass, place the pattern face down on the glass. Tape the edges down with masking tape, and flip the glass over. If you are painting on a cup, place the pattern inside the cup. Move it around until it is where you want it to be. Press the paper against the wall of the cup, and tape it in place. Keep borders in mind. If you are going to put the glass panel inside a frame, make sure that the frame won't be covering your design. Wipe the surface of the glass down with rubbing alcohol. Soak a cotton ball with some rubbing alcohol, and wipe down the entire surface of your glass piece. Any oily residue left on the glass from when you handled it may keep the paint from sticking. Try not to touch the area where the pattern is from now on. Get some glass paint liner and squeeze a tiny amount out onto a sheet of paper. You are doing this, because the first bit of paint often tends to gush out in a glob. It is better for this to happen on a sheet of paper than on your painting. Some glass paint liners are labeled as "leading" or as "dimensional." Most glass liners come in black, but you might also find them in other colors as well, such as silver and gold. Use a glass paint liner or dimensional glass paint to trace the outlines on your pattern. Hold the tip just above the glass, and start tracing the design. Use long, continuous strokes. If you make short strokes, your lines are more likely to end up uneven and goopy. Also, try not to drag the tip on the glass. This will cause the paint to come out too thin and streaky. If you are left-handed, try to start tracing from the right side first. If you are right-handed, start tracing from the left. This will help prevent you from accidentally smudging the wet outline while you work. Make any touchups, if necessary, when you are done. Once you have finished outlining your piece, look over it carefully. If you see any lumps or clumps, you can wipe them away with a Q-tip dipped in rubbing alcohol. If the paint has dried, you can scratch it away with a craft knife. Let the outline dry all the way. Most glass paint liners will take about six to eight hours to dry. You might want to refer to the label on the bottle for a more specific drying time, however, as each brand will be a little different. If you are pressed for time, you can hold a fan or hairdryer over the paint. This will help it dry faster. If you are using a hair dryer, make sure that you are using the lowest setting. Squirt some glass paint onto a pallet or plate. If your glass paint comes with a pointy tip, you can apply the paint to the glass directly from the bottle. You can also squirt the paint onto a pallet and apply it with a paintbrush; this will give you the most control. You can use both synthetic and natural brushes for glass painting. Synthetic brushes may cost less, but they will be more likely to leave behind brush strokes. Brushes made from soft, natural fibers, may be more expensive, but they will leave behind the smoothest finish. Fill in the spaces with glass paint. Do not press down too hard with the brush, or you will wipe the existing paint off. Instead, let the brush glide across the surface that needs to be painted. If the paint is too thin in one area, wait until it dries before applying a second coat. If you try to go over wet paint a second time, you may end up wiping it off. Glass paint will shrink a little when it dries. Try to paint all the way to the outline. If you are having troubles reaching a tight area, such as a point or corner, use a toothpick to spread the paint. The thicker you lay the paint on, the more it will level off. This reduces brush strokes. To create a swirled, marbled effect, put a few drops of two or more colors into the space you want colored. Use a toothpick to lightly swirl the colors together. Do not over-mix, or you may lose the swirled effect and end up with a solid color. Be sure to rinse and dry your brush before moving onto a different color. When you are ready to move on to a new color, dip the brush in water and swirl it about to remove any excess paint. Lightly dab the brush against a paper towel. If you see any color on the towel, rinse the brush again. If you don't see any color, keep tapping the brush until there's no water left on the bristles. If water gets into the paints, it can cause beading. Clean your painting up again, if needed. Look over your piece carefully, and see if there are any places that need touching up. It is much easier to touch things up while the paint is still wet than when it is dry. Use Q-tips, paintbrushes, and toothpicks dipped in rubbing alcohol to wipe away any excess paint. This is especially useful if you went outside the lines. Use a pin or needle to pierce any bubbles that may have formed in the paint. Be sure to do this while the paint is still wet. Read the instructions on the paint bottle. Some brands of paint need to dry for several days before they can be used, while others need to dry for up to a month. Some brands might require you to bake your piece in the oven. Always refer to the label on your bottle of paint. Some labels will tell you to "cure" your paint for a certain amount of time. This simply means to let the paint "dry." Allow the paint to dry for at least 48 hours. After this, the paint should be dry to the touch, and can be gently handled. Depending on the brand of paint you used, however, the paint may not be cured all the way. If the paint feels sticky or gummy, it is not cured and needs to dry longer. Most glass paints will be completely cured after 21 days. Consider baking the item for durable finish. This will allow you to wash your piece in the dishwasher. Place your painted piece onto a foil-covered baking sheet, then put the baking sheet into a cold oven. Set the oven to 350°F (175°C), or whatever temperature the manufacturer recommends. Bake the item for about 30 minutes, then turn the oven off. Do not take the piece out of the oven yet. Instead, let the piece and the oven both cool down first. Removing the glass too soon may cause it to crack. Most paint with glitter in it cannot be cured in the oven. You must allow them to air-cure for 21 days. The label on the bottle will tell you whether or not the paint can be oven-cured. If you are using glass paints from different brands, know that they may have different curing temperatures and times. To avoid burning the paint, stick with the lower baking temperature and time. Know how to wash your glass piece safely. Most glass paints are delicate after they cure, and should only be hand-washed using a soft cloth of sponge. If you cured your piece in the oven, you might be able to wash it in the top rack of a dishwasher. Never leave painted glass sitting in water, even if you oven-cured it. The water will cause the paint to flake away. Also, never use a scratchy sponge on a glass piece; you will scrape the paint off. Finished.  
Gather your supplies. Find a glass piece to paint. Clean the glass with some soap and water. Have your pattern or design ready. Place the pattern where you want it to be. Wipe the surface of the glass down with rubbing alcohol. Get some glass paint liner and squeeze a tiny amount out onto a sheet of paper. Use a glass paint liner or dimensional glass paint to trace the outlines on your pattern. Make any touchups, if necessary, when you are done. Let the outline dry all the way. Squirt some glass paint onto a pallet or plate. Fill in the spaces with glass paint. Be sure to rinse and dry your brush before moving onto a different color. Clean your painting up again, if needed. Read the instructions on the paint bottle. Allow the paint to dry for at least 48 hours. Consider baking the item for durable finish. Know how to wash your glass piece safely. Finished. 