Enamelling is a very complex technique which consists in coating certain pottery with a thick varnish which, after firing at high temperature, makes the latter shiny and more solid. Enamel is therefore used as much to decorate and color a terracotta object as to make it waterproof and more resistant to impact. There are countless enamelling techniques and it takes a lot of experience to master all the intricacies. However, you can learn the basics without too much difficulty and make significant progress with a little practice, provided you have access to a suitable oven.
Part 1 of 4: choosing pottery and glazes
Step 1. Better to start with a cookie
You will find it in a porcelain store or from a specialist craftsman. The biscuit is a porcelain hardened by baking at high temperature, known as “biscuit baking”. Unlike other types of ceramics, the biscuit is porous, which allows it to absorb the enamel when the latter is applied. After a second firing, the enamel hardens and forms a smooth, shiny and impermeable protective layer on the cookie.
- Depending on the base material used for making the object, it will be red or white after the cookie is fired.
- If you prefer to use an object that you have shaped yourself, bake it to harden it, but it should remain porous so that you can apply the enamel on it. The firing temperature depends on the size of the object and the type of material used. Seek advice from an experienced potter if you are unsure of yourself, you might even be allowed to use his professional kiln (possibly at the cost of compensation)!
Step 2. Wear disposable gloves throughout the enamelling process
The cookie of your choice should be as clean as possible, which is why it is important to wear latex gloves when handling the object you are about to glaze. This is because if you touch it with sweaty or oily hands, the enamel may have a hard time penetrating properly. Have spare gloves on hand in case you get dirty while working.
Step 3. Buy ready-made enamel
To start, make your life easier by using ready-made enamels, you can learn how to prepare enamels (which must be grinded, mixed with water, sifted, measured out, etc.) when you have more experience, because this operation requires a mask (the enamel powder contains very fine glass dust). Ready-to-use enamel is also easier to prepare and cook properly.
Step 4. The choice of an enamel depends on its firing temperature
You must choose a preparation whose firing temperature is the same as that of your ceramic, otherwise, the fusion between the two will not take place correctly. If you choose to use multiple glazes, their firing temperature should also be the same, otherwise you risk breaking the pottery or missing the glaze.
The packages may indicate that the cooking temperature is simply “low” or “high”, but you may also notice a “cone value”: “cone 022”; 2; 4, etc. This value comes from the use of pyrometric cones, which are objects to be placed in the firing oven and whose tip bends when the temperature is ideal for the type of ceramic used
Step 5. Attention:
enamels contain elements that are potentially dangerous for your health. Always pay close attention to the makeup of an enamel before buying it. Preparations that contain lead should not be used on a room intended to contain food or drink. Do not use preparations containing harmful elements if you create your enamels with your children or if your workshop or the cupboard in which you store the preparations is accessible to children.
It is possible to cover one layer of lead enamel with a second layer of lead free enamel. If the cooking has been carried out correctly, the object will not be dangerous for health, at least at the beginning. Be aware, however, that after a while the first coat may let the lead through, especially if you often scrub the object in question. Some foods with high acidity, such as tomatoes, will have the same effect. You should stop using the pottery if you find that the enamel is crumbling or cracking
Step 6. To add color to your pottery, you can paint it by applying enamel undercoats
You can use as many colors as you want to decorate your pottery. Be careful, choose the products according to their color after cooking. With heat, these underlayments undergo chemical modification and their color can change completely. To avoid disappointment, you should check the packaging for the final color of the product.
Step 7. Purchase extra glazing
Even if you don't use an undercoat to decorate your pottery, you should apply an overglaze coat. It is this which gives a shiny appearance to the pottery and makes it more resistant. You can choose it transparent if you have painted your pottery or colored, a wide choice of colors is available to you.
Note: here again, you must choose products whose cooking temperature is the same as that of the shard itself. If you do not respect this rule, your pottery could be damaged during firing
Part 2 of 4: prepare the ceramic and enamel
Step 1. Begin by sanding the pottery to remove imperfections
There are often small irregularities on a shard, but these are easily removed with 100 grit sandpaper. When you have a smooth surface, gently dab the object with a damp sponge to remove dust accumulated during sanding.
If you bought a ready-made item from a store, this step shouldn't be necessary
Step 2. Dab the entire surface of the pottery with a damp sponge before applying the enamel
Clean again any part that gets dirty as you work. The damp sponge will also be used to remove an overflow of enamel. However, do not soak the cookie in water too much and do not drop large drops on it. Do not overuse the sponge and make sure you have several on hand because each side is quickly soiled.
Remember to wear gloves to avoid getting too much dirt or grease on the cookie with your fingers
Step 3. Coat the base of the pottery with a layer of protective wax
You must also put it on all the contact areas between two removable parts. The enamel does not adhere to the wax, which is important. If the base of the object is coated with enamel and placed on the baking sheet of the oven as it is, you will not be able to peel it off, because the enamel will have fused with the plate during baking! It is for this reason that it is also necessary to put a wax pad between two removable elements, such as a cover and its base or any place where two different parts will be in contact during cooking. You can use paraffin wax or, even better, a wax emulsion specially made for ceramics that you find at art supply stores. The latter also smells much less strong. The wax is applied with a brush and the one you use for this purpose should not be used to apply the enamels.
- You can also rub crayons on the pottery, but the colors may leave permanent marks on it.
- For children, the waxing stage is complicated. One solution is to glue the enameled piece on a clay base just before firing to collect the enamel drips.
Step 4. For your safety, if you prepare your enamels yourself, strictly follow the instructions provided with the ingredients
However, consider making your first creations with ready-to-use enamels, as mixing enamel powders is delicate and potentially hazardous to health. If that doesn't scare you, don't do your preparation out of the blue. Read the instructions on the packaging carefully, otherwise you risk missing the enameling of your pottery. In all cases, you must imperatively wear a mask during preparation so as not to inhale enamel particles and the room where you work should be well ventilated. No one else should approach your countertop without wearing a face shield, of course. Also remember to wear protective glasses and gloves.
We cannot detail here all the stages of preparation of the enamels, as they differ from one product to another, but you will need water, a long-handled spoon or a ladle to mix and a hydrometer to measure the density of the mixture. The ideal density of the enamel bath depends on the type of terracotta you want to glaze
Part 3 of 4: apply enamel
Step 1. Mix the enamel bath well
Even ready-to-use enamel sometimes needs to be stirred well to achieve a homogeneous consistency. Check the instructions given on the packaging for a successful preparation: there should not be a thick deposit at the bottom of the tank, nor should there be a layer of water on the surface of the mixture.
Step 2. Pour each preparation into a small container and prepare a brush for each different enamel
Colors should not be mixed, which is why you need a brush for each different preparation. Enamels keep very well in airtight, clean jars, which is why it's best to pour just the amount you need at the moment into a smaller container instead of dipping your brush directly into the mixture, using risk of contaminating it.
Step 3. Apply the undercoats with a brush
Use the underlays to decorate your pottery as you like. There are dozens of possible techniques to let your creativity run wild: you can paint, splash, let the enamel flow freely, shake your brush, you can even spray the enamel on the pottery if you want to get a color. evenly distributed over the surface of your object.
- Remember that colored glazes may change color during firing.
- Dripping is a very popular technique with many ceramicists, but be aware that if a drop is too thick it can change the texture of the cookie and react badly to firing.
Step 4. To remove excess enamel, scrape it off with a knife or any metal object
It can happen that you apply too much enamel, that it starts to drip or that you put some in the wrong place. Simply remove it by scraping it with a knife before cleaning the cookie with a wet sponge.
Then clean the knife in hot, soapy water
Step 5. If you want to lay enamel inside a hollow pottery, but has a narrow neck, you cannot do it with a brush
For hollow items such as pots or vases, the neck may be too narrow for you to run your brush through. In this case, you can run a small amount of enamel inside the pottery before taking it with both hands (with gloves) and spinning it around so that the enamel layer coalesces. spreads over the entire interior surface.
Step 6. Wait until the first coat of enamel is completely dry before applying the second
You should wait until a coat of enamel is completely dry before applying a new one, whether it is another color undercoat or the final overcoat. Drying is faster if you put the object in a well ventilated area. The appearance of the enamel changes when it has dried, it no longer looks shiny or wet, and no longer clumps when you run your brush over it.
Step 7. Apply the final overcoat
The easiest way to apply the final coat of enamel is to immerse the object in a bath with a pair of enamel pliers. The pottery should only be immersed in the bath for a few seconds, three at most. You can repeat the operation several times if you want to obtain a thick and shiny finish, but always allowing each coat to dry well before adding a new one.
The overcoat can also be applied with a brush. Completely cover your pottery with a thin layer of enamel. Better to apply two thin coats than one thick coat
Step 8. Remove the enamel from all parts of the object that will be in contact with the baking sheet
While baking, the enamel fuses like glue and if it attaches to the baking sheet or a nearby object, there is nothing more to do. To avoid this, the bases of the pottery and the removable parts in contact are protected by a layer of wax. It is easy to remove the enamel from the wax with a damp sponge.
- You must remove the enamel from the base and other parts after each application of a new coat, before it has dried.
- If your enamel is too runny or drips a lot, you can avoid applying it to the bottom of your object. Leave an area of 6mm or more without glaze at the bottom of the pottery. Many professionals do this.
Part 4 of 4: bake the enamel
Step 1. Find a place to cook your items
A ceramic kiln is expensive, before investing in such equipment, you can look for a pottery workshop near you where you can have access to a kiln. This service is not free, but you can rent a cooking space for your creations in a collective oven. If you live in the city, do an Internet search and you will probably find a workshop near you.
Use the Yellow Pages or search for keywords, such as “shared ceramic kiln” or “pottery workshop” on the Internet to find the workshop closest to you
Step 2. Don't start buying and using your own oven without seeking professional advice
If you decide to invest in a ceramic kiln, start with a mobile electric kiln. There are many criteria to take into account: price, power, additional equipment to buy, in particular. Using a ceramic kiln is neither easy nor risk free, which is why it is strongly recommended that you get help from someone with experience at the start.
Step 3. Proceed with the firing of the enamels according to the instructions given on the packaging of the powders you used
Some glazes bake at low temperatures, others at high temperatures. If you do not respect this temperature, you risk bursting the terracotta or failing to melt the enamel layer. Set your oven to the correct "cone" of temperature, as indicated on the packaging of the enamel powder.
If you are using an oven in a shared workshop and someone else is baking your item, be sure to include a note with it specifying the temperature at which it should be baked
Step 4. The cooking time varies
There are many different pottery techniques and all require different firing times, sometimes up to 24 hours. By definition, the firing of pottery is a slow process and the objects must also cool completely afterwards. If you are using a collective oven, you will often have to wait several days before you can collect your item.
During cooking, the layers of wax will disappear. If you still find traces of it or if it fuses with the enamel, use a different type of wax next time
- Clean your equipment thoroughly as often as possible: the different materials should not be mixed. Keep wax and enamel brushes separate until they have been properly cleaned.
- There are hundreds of kinds of ceramics and enamels. You can discover new techniques and materials by participating in courses with professional potters or by consulting specialized books.