The glazes for ceramics are mixtures that melt with the ceramic when heated in the oven and are used both to decorate and to create a pleasant glossy surface that protects it from use and water. The enamelling process can be long and laborious but it is not too difficult to learn and the result will improve with practice. If you don't have access to an oven, try to find one before you begin, as indicated in the "Enamel Firing" section below.
Steps
Part 1 of 4: Choosing the Ceramics and Glazes
Step 1. Start with a hardened, unglazed ceramic
A pottery shop or artist will be able to suggest suitable items for sale. Normally these are objects called "biscuits" for having already undergone the first cooking process and therefore hardening. Unlike some fired ceramics, the "biscuit" has a porous surface that can easily absorb the wet glaze which in turn will create the protective waterproof layer when the ceramic is fired for the second time.
- Depending on the type of clay used, the biscuit ceramic can be white or red.
- If you have a clay object that you made yourself, before glazing it, bake it in the oven to harden it while keeping it porous. The exact firing temperature depends on the size of your object and the type of clay it is made of, so if possible ask an expert ceramist for advice. Who knows maybe one of them will be willing to let you use his oven even though he will probably ask you to pay for the service.
Step 2. Use disposable gloves while handling the ceramic
The "biscuit" ceramic you are about to glaze must be as clean as possible. Even the grease on your hands can affect the correct sealing of the enamel, so when you touch the object to be enameled use disposable latex gloves. Change them every time they get dirty before touching the ceramic again.
Step 3. Buy Nail Polish Blends
If you decide to make your own nail polish using powder and water, remember to wear a mask to avoid inhaling what are actually glass dust particles. If you have never prepared glaze yourself, we suggest you use commercially available glaze blends, which by the way cause fewer problems when firing.
Step 4. Choose glazes based on their firing temperatures
Different glazes require different firing temperatures to set properly on ceramic. Do not use two glazes on the same object that require different firing temperatures, otherwise you risk breaking the ceramic.
Firing temperatures can be indicated with the terms "high" or "low", or in units of measurement "cone Orton 2", "cone Orton 4" etc. These measurements refer to cones made by potters with different types of clay that curve at different temperatures in the oven
Step 5. Beware of dangerous ingredients
Before buying nail polish, ask what the ingredients are. Lead-based external enamels are not suitable for objects that then come into contact with food or drink. Toxic glazes of any kind are not recommended if there are children involved in the process or if they have access to the glaze storage area.
For starters, a lead-based decorative glaze with a second coat of non-lead-based lacquer will do if the glaze is cooked properly. However, lead can surface through the glaze even after prolonged use of the object, especially if the ceramic is rubbed often or if it is exposed to foods with a high acid content such as tomatoes. Do not use dishes if you see traces of dust or cracks on the enamel surface
Step 6. Buy one or more glazes based on the colors they will have after firing
Decorative glazes come in many varieties of colors and are used to decorate or paint ceramic. You can use any colors you want to decorate your vase. However, keep in mind that the glazes inside the oven are subjected to a chemical process that can alter their color in an extreme way. Look at the colors of the supplier's nail polish chart to see an example of the final color that the glaze will take. Do not think that once the glaze is fired it has the same shade as it had before firing.
Step 7. Buy a final hairspray
Whether or not you decide to decorate your ceramic object with glazes, you will always need a final lacquer. This allows you to obtain a glossy protective film. Choose a clear lacquer that does not cover the colors of the decorations below, or, if you have not used decorations, choose one of any color.
Note: As noted above, if you are using multiple glazes on your vase, you must use glazes that bake at the same temperature. If you cook enamel at the wrong temperature, your object could be damaged
Part 2 of 4: Prepare the Ceramics and Glazes
Step 1. Remove imperfections from the surface
If you find that the object has imperfections or bumps that shouldn't be there, sand the surface using 100 grit sandpaper. Be sure to dust it with a damp cloth to remove the dust caused by the sanding operation.
If you have purchased a ceramic to be glazed, the imperfections should have already been eliminated
Step 2. Clean the ceramic with a damp cloth before starting and whenever it gets dirty
Before you begin, and whenever your ceramic gets dirty or you apply too much glaze, clean it with a damp cloth. Avoid washing or dripping water on the ceramic and use take care to keep the cloth as clean as possible; it wouldn't be bad if you had more than one available.
Remember that when you have ceramic in your hand you should always use disposable gloves to avoid dirtying or greasing its surface
Step 3. Apply some wax to the base of your object and to each point of contact between two parts that must remain separate
A coat of wax prevents the glaze from adhering to the base of the ceramic, where it would "stick" to the base of the oven during firing. For the same reason, when there is a lid, apply wax to the rim and anywhere else where two distinct pieces will touch. Some potters use a slightly heated type of paraffin wax, however pottery or art supply stores sell a "tough wax" made especially for these cases which is a safer and less smelly option. You can use this wax by applying it with a brush. Then keep the brush away from the glazes.
- You can also use wax crayons to create a veil of wax on the object, but there is a risk that the colors of the crayons will be absorbed by the ceramic.
- If you are glazing ceramic with the help of children, perhaps it is best if you skip this step and hot glue the glazed objects by the children onto a clay disc before firing them, so that the base collects the excess glaze drops..
Step 4. If you mix the nail polishes yourself, carefully follow the instructions and safety procedures
For (at least) the first projects we recommend a ready mix given the dangers and difficulties involved in mixing glazes on your own. If you decide to mix dry nail polish powder with water, follow the manufacturer's instructions carefully otherwise your nail polish will not give the desired results. Always wear a mask on your face to avoid inhaling dry nail polish particles and work outside or in a well-ventilated room. Do not allow anyone to approach the work area without wearing a breathing mask. The use of gloves and safety glasses is recommended.
We do not give you all the instructions here because there are too many variations between the different blends. But normally you will need water, a spoon to mix and a hydrometer to check the density or "specific gravity" of the glaze
Part 3 of 4: Applying the Nail Polish
Step 1. Mix each nail polish carefully
Even if you have purchased a ready-made blend, it may be necessary to mix it before application for it to acquire a homogeneous consistency. Follow the instructions on the package and mix until there are no more lumps on the bottom or watery layers on the surface.
Step 2. Pour each nail polish onto a saucer and match it with its own brush
Keep the colors separate and use different brushes to avoid contamination. Pour them into a small container rather than dipping the brush directly into the jar. This allows you to keep the polish clean for future work.
Step 3. Apply the background decoration with the brushes
Decorate the object in any way you like using brushes dipped in blends. This is an ongoing process and you can decide to unleash your creativity and let the color run or flow, or spray it if you want to get a different effect from the brushstroke. You can also decide to cover the entire surface with a single glaze if you want to get a simple and solid color.
- When deciding on a type of design, always remember what the final color of each nail polish will be.
- Pottery artists often use the drop effect, but be careful because too thick drops can alter the structure of the ceramic and cause problems during firing.
Step 4. Use a metal object to remove any polish you don't want
If you apply nail polish in the wrong area, or if it starts to run, remove it with a knife or metal object and then wipe with a damp cloth.
Thoroughly clean the knife with warm soapy water before using it again in the kitchen
Step 5. Glaze the inside of containers that have a narrow opening
If you are glazing a ceramic vase, cup, or object with an inside surface, it may be difficult to see inside or reach the area with the brush. In this case, pour a small amount of polish inside and using the gloves rotate and move the object so that the polish applies evenly to the inner walls.
Step 6. Let each layer of nail polish dry before applying the next one
Before trying to apply a different color of glaze, or the final lacquer, you must wait until your ceramic object is dry. To speed up this process, leave it in a well-ventilated area. Do not apply a second type of nail polish while the first layer is still wet and shiny and wait until you can touch it with the brush without leaving a trace.
Step 7. Finish with a hairspray
If you have ceramic tongs available, the easiest way is to grab the object with tongs and dip it into the lacquer container for a second or two. If you want a thicker, shinier finish, soak the item for a short time, let it dry, and then soak it again. You can dive it multiple times but the total time of all dives should not exceed three seconds
You can also apply the hairspray with the brush. In this way the surface will be completely covered with a thin layer of lacquer. Allow the ceramic to dry before applying a second coat rather than applying too much lacquer at one time
Step 8. Remove the lacquer from surfaces that could stick to the base of the oven and from any other parts in the oven that come into contact with other ceramic objects such as a lid
If you followed the instructions above, the base of your item will be coated with wax and this will make it easier for you to clean up residue of polish that would otherwise stick your item to the base of the oven. Use a clean, damp cloth.
- Also clean all these surfaces after each nail polish application and before it dries.
- If the glaze drips noticeably it is best to leave a 6 mm or more of unglazed surface on the bottom. Many professional artists also use this method.
Part 4 of 4: Enamel firing
Step 1. Look for a publicly accessible oven
Buying your oven can be very expensive. If you live near an urban area, chances are there are potters' workshops that allow anyone to rent the kiln. Search the internet to see which kilns are in your area or which pottery workshops you could contact to rent a space in their kiln.
If you live in the US this link can help you, although there are many others that don't appear in the list
Step 2. Ask for assistance if you need to buy or use an oven
If you eventually need to buy one you will probably want to buy it portable and electric. There are several factors to consider, including the expense involved, electrical hookups, and what other equipment should be purchased as well. The cooking operation in the oven is complex and potentially dangerous and at least for the first few times it is better if you seek the guidance of an expert ceramist.
Step 3. Cook the glaze following the instructions
The glazes are at low or high temperature and firing them at the wrong temperatures can cause the ceramic to crack or the glaze to detach. Make sure the oven you are using is set to the correct "cone" as indicated on the enamel package.
If you take your ceramic to an atelier to be baked for you, accompany it with a note showing the firing temperature. But don't stick the note directly on the enameled object
Step 4. Go get your pottery a few hours later
There are several ways to operate an oven and some processes can take longer than others. Whatever the procedure, you will have to wait several hours of cooking before your ceramic is ready and, if the oven is used by more people, you may have to wait even a day or two. After cooking and cooling, you can take home and admire your ceramic creation.
The wax layer during baking will melt. However, if the wax is still stuck to the bottom or has fused with the glaze, use a different one next time
Advice
- Clean materials often to avoid contamination. Keep wax brushes separate from nail polish brushes unless they are perfectly clean between uses.
- There are hundreds of types of pottery and glazes. An experienced potter or a dedicated pottery instruction book can teach you many other ways to decorate pottery or create unique effects with glaze.
