Mastering Ceramic Glaze and The Must Know Tips on Using It

  • Time to read: 20 min.
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The complete work of pottery includes creating various shapes and then finishing off the art along with the application of glaze. Glazing sets each of the pots apart from another, which renders uniqueness to every piece. This extensive part of pottery decoration includes a heap of techniques and tricks that the potters use to create their masterpieces.

 

The work of glazing thus needs to be mastered with proper skill and efficiency. Glazing is very important, and you need to apply it properly to make the pot look more beautiful.  The work of glazing is quite labor-intensive and requires proper knowledge of colorants to acquire the desired shade and decoration.

 

However, there are a few things that you need to know. There are factors that come along with mastering ceramic glazing, and this post will discuss what they are, all about the different types of glazes, and why you need to glaze your stuff. You’ll be able to, by the end of this, become a glazing master

 

Okay, but why Glaze?

Why should you glaze? Well glazing is actually a big part of pottery, and it gives several different purposes, That’s because it does the following:

 

  • It adds a coating to bisque wares
  • It makes it waterproof
  • It makes them safe for food
  • It helps bring more color to the piece itself
  • You have way more options with this

 

Or many, the possibilities that you get with glazing are practically endless, and the patterns, along with the techniques that you have, will allow you to create this without any sort of limit. If you feel like your pottery is kind of bland and boring, then start trying this, since it can make anything that’s ordinary look extraordinary, and also a lot more like art.

 

However, with pottery glazes, there are a lot of different actors that go into this that’s because they’re made up of chemicals, and in a basic sense, these chemicals, along with the compounds, actually react to the clays and the material in a whole lot of different ways, That means, that you may not always get the same result each time that you do this.

 

Glazes react a lot different depending on what you use with them; the possibilities that you have with this are endless, but remember, you want to use this correctly to create different and worthwhile pieces that will help you take your work to the next level.

 

You will want to always bisque ire before using these glazes. That’s because:

  • The glazes tend to be absorbed
  • The single-fired pieces tend to be used for decorative means rather than actual uses
  • It is much harder to work with something that isn’t bisque fired

Now that you know why you do it, let’s discuss the factors and all the different types of glazes that you can try out.

 

The Factors that involve this

Many glazes, they’re affected by the clay, stains, and slips, along with underglazes. However, most of the time, the metallic oxides are what you see that determine a lot of this; there are three main factors that affect the glaze color and the overall look of the pottery. This is important to learn because if you’re going to be going into pottery making, and you want to experiment with glazes, knowing these three factors can make a major difference in your life.

 

These three actors are, in essence, the umbrella which each of the other variables falls under. They are:

 

  • Glaze composition: not just the colorants within this, but the materials within the glaze that, in the essence effect, the colorant, or this combination. For getting optimum results, you can use a good quality readymade glaze, like Mayco Stroke & Coat Wonderglaze Glaze.

 

  • Temperature: if you fire this at certain temperatures that you’re using, it actually can affect this. For example, some of the glaze colorants are actually quite volatile, and it will dissipate and move off the piece if this goes too high. In contrast, when it’s too low, it can affect the overall colors. The temperatures play a huge part in this.

 

  • The atmosphere of the kiln: this goes along with what was said before, but in essence, sometimes during firing and cooling, you can see different factors that affect this.

 

  • Firing schedule: It is also essential to ensure a proper firing schedule for better application of the glaze on the pot. So, here is a guide for your firing schedule.

 

Temperature

Ramp hour

150-degree Fahrenheit / hour 2 hours
400-degree Fahrenheit / hour 3 hours
120-degree Fahrenheit/ hour Until it reaches the temperature

 

 

These four factors are what you should watch out for, and with these four factors in place, you’ll have a better idea of what it takes to really take your kiln firing and your glazing to the next level.

 

Now that you know what affects this, let’s talk about each of the glazes and how they can be affected by the atmosphere of the kiln.

 

Chromium oxide

With chromium oxide, you’re essentially getting a whole bunch of different colors, including red, pink, brown, yellow, but most of all green. There are a few factors that you’ll need to watch out for with this, and it’s actually quite volatile once you get past cone 6 or so, and you might notice that if you do fire it higher, it causes a smoky effect, which may be what you’re going for.

 

 

Here are a few things to know about each of them and what color you should watch out for:

 

  • If it’s chrome red, you have it at the firing of cone 08 or lower. However, this is toxic and shouldn’t be used in functional wares
  • Chrome and zinc give you a brown, which makes it functional
  • Chrome that goes yellow needs to have a lead-soda fire glaze at around cone 08 or lower than that. However, if it goes higher, it’ll turn green. This is also extremely toxic, so don’t use this in food ware
  • Chrome and tin give you either pink, warm brown, or gray pink. This is all dependent on what parts of the oxides in the glaze related to one another
  • Chrome plus cobalt give you a teal color when fired past cone 9 or so, and it also is fired in a reduced atmosphere, Any magnesia glazes are added to this, and they can create nicer colors if that’s what you’re going for, You’ll definitely want to play around with this

 

For many potters, using chrome coloring and glazes are the way to go, because this is typically how they get their colors. There are different factors that affect this, and you can mess around with these if that’s what you feel like doing.

 

Cobalt Oxide with a Cobalt Carbonate

 

Ceramic Glaze

 

This is another type of powerful colorant glaze that you can try. This one, in particular, will almost always give you a blue, due to the cobalt within it.  Typically, if you’re looking to have a good sort of glaze to work with that isn’t too intense or the firing, and has a better particle size to work with, this is the way to go. However, there are a few things that you should know about when mixing these two factors together, and some things that are worth keeping in mind.

 

  • Cobalt with manganese and iron will give you a very powerful and intense black, which may make it hard to see any staining on there
  • Magnesia and cobalt, when fired at cone 9 or higher, can give you a blue that’s mottled with pinks, purples, and reds. However, this is extremely hard to control and very hard to actually replicate once more due to the temperature range being extremely narrow and the atmosphere you’re firing in
  • Cobalt with rutile gives you streaked and mottled looks to it
  • If you have a glaze that’s high in magnesia, you’ll notice that when you fire, the very small levels of cobalt will give you a color range that goes from blue-violet to pink

 

This is another pretty volatile set of colors and glazes, and you should mess around with this before you begin with it, to see if that will work, remember, if you’re going for blue, this is ultimately the way to go.

 

Copper Oxide and Copper Carbonate

Another very popular type of glaze is a copper one, That’s because it’s got a very strong flux to this,
which can make a glazed area much glossier. However, if you fire this past cone 8 or over this, the copper will be extremely volatile, and it will start to jump, If you’re going to oxidize it, it’ll be green, but if you want to reduce it, you should make it red. Typically, copper oxide is often more intense than copper carbonate, but both of them often do the same, it just determines what you’re going to get in terms of the extent of color.

 

Where are a few things that you should know about when firing with copper oxide, or copper carbonate?

 

  • Copper gives a very nice range of greens when you’re using a lead glaze. Typically, though, copper does increase the solubility of lead, which is toxic, and should only be used when you’re creating decorative ware
  • Typically, copper fired with glazes high in barium does give a very pretty blue, or a blue-green, and this is done in both a reduced and oxidized atmosphere. However, barium is toxic, so don’t use this in functional ware
  • Copper is an alkaline glaze that will create a turquoise, and this is because of its ability or to be in an oxidized atmosphere
  • If you low fire raku copper, it will give you a very metallic-looking copper, which is often seen in raku pottery. However, as time goes on, the glaze will start to oxidize and become green

 

What About Iron Oxides?

Iron oxides are actually a much more challenging type of glaze to work with. However, it’s also one of the most important types of glazes to work in some cases, especially when it comes to colorants.

 

That’s because of the following factors:

  • There is naturally occurring iron in a wealth of clay bodies
  • You can get a variety of colors with this

 

That makes sits a bit challenging, especially if you’re going or a specific color. For example, if you’re trying to understand the gamut of glazes, just know that most of the clay bodies go from light gray to deep brown. When there are clear glazes, most of the iron clay bodies have a very similar sort of color range in many cases.

 

Typically, bodies that contain iron in them are fired but they aren’t mature, Most of the clay bisque ware pieces that you work with are actually something that falls into this. In many cases, using iron oxides will give you a yellowish or a salmon pink color in time. If you see a pot that’s glazed with a glaze that’s lower in temperature, and it’s fired below the maturity temperature of the body itself, it will give either ocher, salmon, or a reddish-brown color in many cases when you’re making the piece itself.

 

There are also different types of iron oxides when it comes to glazes. Typically, most of the time the iron in this is the red iron oxide that you probably are familiar with. This is called ferric oxide. However, there are a few factors in this:

 

  • Red iron oxides have similar properties to the yellow iron oxide
  • Yellow iron oxide is another type of ferric oxide, so it’s similar, but it has a very different color when you fire
  • Black iron oxide is called ferrous oxide, and typically is much coarser than the others, and not used as much
  • Crocus Martis is an iron oxide that’s impure, and it can leave some speckled, spotty, or rough effects

 

Now, the following are the different types of iron oxides, which are used in glazing pots.

 

 Type of iron oxide

Formula 

Color 

Ferric oxide or Colcothar  FeO3 Red
Ferric oxide hydrate  FeO (OH) Yellow
Ferric oxide or Iron (III)   Fe2O3 Red-brown
Ferric Ferrous Oxide  Fe3O4 Black

 

 

The type of iron oxide that you use in the pottery does determine this, and you should spend some time going over this. Generally. However, iron creates a warm color that goes from light tan to a straw color, to even a deep rich brown. You just have to experiment with this. However, there are a few little rules that you can follow when you’re using iron oxide glazes.

 

  • The high fire ones that contain bone ash along with iron create a persimmon red or an orange color
  • Iron is the type of chemical that has a flux ability when it’s in a reduced atmosphere. It’s much less active in some cases compared to refractory oxidation areas of atmospheres
  • Those that have iron and tin within them that is a high fire in terms of glazes give a color that’s mottled and creamy in color, and it does create a red-brown in many different areas
  • An iron that’s in a high fire reduction creates an iron blue that’s very delicate, and also one that’s a celadon green in some cases
  • Those iron content that’s high fire and has a high level of iron in them will give you a very glossy looking dark brown or even a brownish-black in some cases. In areas that are thin, the iron might begin to oxidize when it cools down. This, in turn, will cause areas to turn red, and from there, you get red highlights from this as well.

 

Iron oxide is a very interesting material to work with because of its nature of this, and you’ll notice as well the difference that this makes when you’re working with it, and what it can do for you.

 

Manganese Dioxide

This is another type of glaze that you can use. Typically, it’s introduced in the form of manganese carbonate, so if you see this on the bottle itself, it’s that, if it’s black, typically it’s used in clay bodies and slips, which gives splotches and spots. However, compared to copper and other colorants, manganese is actually very weak. This is another type of glaze that often isn’t used all that much due to the fact that it is actually very toxic, so you need to utilize the safety precautions that you need to in order to achieve this.

 

 

Ceramic Glaze

 

There are a few coloring factors that go along with this, and they are as follows:

 

  • In glazes that are high in alkaline, manganese will give you a blue-purple or a plum color
  • Above cone six, this produces a brown color in the pottery
  • If you’re using a lead glaze, the manganese will give you a purple that’s soft, but with brown tinges in it. However, this is extremely toxic, so don’t use this in functional ware

 

Nickel Oxide

This is probably one of the most unpredictable glazes since when you’re just using it itself without anything else, it gives results that are extremely unpredictable, due to its volatile nature of it, which means that it can be anything from gray to brown. However, if you use this with another colorant, you will notice that it will tone down the other colorants that are produced, so if you want to reduce the presence of a color that’s created in a chemical, this is ultimately the way to do it.

 

Rutile

Rutile is a titanium ore that’s not pure, and it contains iron, along with other materials. This is actually one of the more interesting colorants since it generally creates a tan when oxidized, and a gray when it’s reduced. For rutile, it actually encourages the growth of crystals that are present in mid-range and also high-fire glazes. It is actually used to create streaky and mottled effects in pottery.

 

There are a few different factors that are associated with rutile, and they are as follows:

  • If you use rutile that has boron in it, it will give streaks or spots that are very pronounced, and if you mix this with other colorants, you can create some interesting streaky colors due to the nature of how it works together
  • Rutile will change the opacity, increasing this
  • If the glaze is fluid, the rutile will encourage the blues to be opalescent in a sense

 

Rutile is good if you want to introduce more opacity into the piece that you’re making. But, as always, be careful of the mixing of said colors

 

Are there other Colorants?

 

 Ceramic Glaze

 

 

Yes, there are other colorants that you can use in order to change the nature of your pottery.

 

  • Antimony: used to create a yellow in glazes that fire low
  • Gold gives you a pink, red, or purple range
  • Cadmium and selenium together give extremely bright reds, but they burn out very easily. However, they’re also toxic, so don’t use them in functional ware
  • Ilmenite is a colorant that works similar to an iron oxide that’s black
  • Platinum gives a gray
  • Silver and bismuth give a luster overglaze and are great for that
  • Iron chromate gives you a shade of either gray, black, or brown, and typically, adding this with tin together will give you a pink, or a brownish-red. However, if you do this with a brush, it actually will give a black haze to it that has a pink halo to it. with this one, in particular, it’s actually toxic, so definitely don’t use this for functional ware, and also handle this with care, and the proper safety tips
  • Uranium oxide gives you a red, yellow, or coral color. However, even when you fire in a glaze, it’ll be radioactive, so if you’re trying to stay away from radiation, don’t use this. as an aside as well, it is toxic, so you should handle this with care as long as you’re able to really create the glaze that you want

 

With all of these it’s super, super, super important that you make sure that you do handle these carefully, and if they are toxic, incorporate the proper measures to actually take care of this, and make sure that if you mix these chemicals together, you know what will be toxic, and what won’t be. Pottery glazing is quite fun, but it’s important to remember that you’re going to be working with volatile chemicals, and often, these may act in different ways. Plus, sometimes combining the wrong chemical together will produce a result that’s often not something you want to deal with. If that’s the case, you’ll need to read up on the glaze, check the bottle, and see how it can be mixed, so that you’re able to create the best and prettiest pottery that you can, but also pottery that will be safe to use, and pottery that isn’t too volatile or anything. definitely work to achieve this, and play around with the glazes, especially if you think it’ll end up looking cool later on.

 

Tips that you need to follow to master the art of glazing

To ensure the proper application of glazing and a top-notch result, the first thing you need to ensure is the appropriate application of the glaze mixture and the right way of firing. But before knowing that, you need to learn about the mistakes that you must avoid while glazing your pottery.

 

Here are mistakes that you need to avoid.

 

Glazing problems 

Reasons

Shivering Using a lower expansion glaze compared to the clay body
Crazing Using a higher expansion clay compared to the clay body
Blisters Inappropriate application with improper preparation
Crawling Drying the underglaze before applying the overglaze
Pin holing Improper control of the firing cycle
Settling Using contaminated or bacteria-affected clay.

 

 

Here are a few more tips that you can nurture to become a pro in ceramic glazing. Let’s have a look:

 

 

 

  • Sand your bisque ware properly: Before applying the glaze, it is crucial to ensure no dust or grime is present on the bisque ware’s body. The best thing you can do to get rid of all the dust is, to use sandpaper to rub onto the body of the bisque fired pottery to get rid of all the unwanted dust. Rub the sandpaper evenly everywhere to get rid of all the sharp bumps, and rough edges.  You can make your sandpaper a bit damp before using it on the pottery surface to prevent the spreading of dust.

 

  • Properly clean the bisque ware: The glazing is not going to adhere properly if there is any kind of dirt or oiliness. It is best to clean your bisque ware using a damp sponge or a cloth to eliminate all the unwanted debris to ensure a nice glaze bond on the pottery surface. To get the best results, you can submerge your pottery in a bucket full of water, or you can rinse it thoroughly with running water. Then allow it to become evenly dry before applying the glazing mixture on the top of the pottery surface.

 

  • Get rid of oil on your pottery surface: If there is any oil on the surface of your pottery, the glazing is not going to stick to it. To ensure the proper application of glaze on the surface of your ceramic, make sure that you are keeping your bisque ware away from any kind of oils or lotions. Also, the natural oils from your hands can disrupt the process. And that is why it is better to clean your hand properly while working with your pottery, or you can use rubber gloves to prevent your hand’s moisture from disrupting your glazing process.

 

  • Mix your glaze adequately before applying it: Irrespective of what glazing application technique you are using for your pottery glazing, you need to make sure that the mixture you have prepared is of the proper consistency. Mix your glaze properly by stirring it to ensure there are no lumps or crystallizing in the process. After preparing the mixture, make it pass through a sieve to get rid of bubbles or particles that can make the smooth mixture suffer. To ensure the proper thickness of the glazing is also essential. The right consistency is not much thick or thin; instead, it is milky and creamy.

 

  • Proper application of the ceramic glaze: While applying the glaze mixture, make sure you are using the appropriate technique. While applying one coat of your glazing, opt for an even application all over. Make sure you are not streaking while adding the glazing. To avoid sticking, it is vital to ensure that you are not applying too much thin coat of glazing. Too much runny glaze is going to ruin your entire glazing and leads to messiness. If you are using the brushing technique, it is better to keep changing the direction of the brush while applying. If you have applied the vertical application initially, make sure the second one is horizontal or diagonal. Start with glazing the inside area first, then move to the outer space to ensure a hassle-free application. You can use the Creative Mark Hake Paintbrush Set.

 

  • Ensure a proper drying process: While applying a glaze, it is essential to dry it properly. In case you are working with several glazing coats, you need to dry each of the coatings before applying the second one. Or else it is going to ruin the entire application. It is better to dry out each coat and go to the next one.

 

  • Make sure there exist no bubbles in the glazing mixture: The first thing you need to keep in mind while applying the glaze mixture is, getting rid of any kind of bubbles present in the mix. After mixing the glaze properly, get rid of all the bubbles if you are planning to dip your pottery in the glazing mixture. The trick is to slowly stir the mixture and strain it properly.

 

  • Remove the extra glazing: If the glaze is dripping from an area, then it is because there is too much glazing in one point. If the glazing is dripping from an area where you have already applied the glaze, merely wipe it off. But make sure that you are doing it after the glaze application is completely dry. Once it is completely dry, use a cleanup tool, metal rib, or sandpaper to remove any type of extra glaze.

 

  • Avoid contamination: Your glaze can get contaminated if you are not working in an organized manner. To avoid contamination, rinse your brush and other tools properly before using them for a fresh batch. While using a brush, the mixture is going to run towards the handle. Make sure you are wiping it properly or wipe it off to prevent any kind of contamination.

 

  • Dry appropriately before firing: It is crucial to ensure that you are correctly drying your glaze before putting the ceramic ware inside the kiln. The kiln will not react in a friendly manner if it comes in contact with the wetness or even slight moisture. It can completely explode inside the kiln, which is going to break your pottery. Before exposing your glazed pottery to the fire of the kiln, opt for drying it properly. Touch your pottery to know if it is feeling cool to your touch or not. If it still feels cool, then you need to wait for some more time to make it completely dry before putting it inside the kiln to avoid any kind of unwanted accidents.

 

Tools that you are going to need for beautiful pottery glazing:

The work of glazing needs lots of tools, which are essential to get the best pottery-making results.

 

Here are the tools that you are going to need for your ceramic glazing.

 

Tools

Why do you need them?

Spatula To mix the small amount of glaze properly
Whisk Whisk ensures a first and even mixing of the glaze
Sieve To strain the glaze mixture
Brush For applying the glaze mixture
Banding wheel To make the ceramic spin for a first glaze application
Tongs To make the ceramic dip into the glazing mixture
Glaze bulb applicator To add a detailed application of glaze with the liner decoration

 

 

Conclusion:

Ensure that you are using all the suitable colorants and the techniques mentioned above to get the best results with your pottery making from the very beginning. At the same time, you need to ensure that you are avoiding all eh unnecessary mistakes that can ruin your entire effort of glazing your pottery. The best way to ensure this is to stick to all the tips from the very beginning. And the more you practice, the more you are going to unleash better and more innovative techniques.

 

 Happy sculpting!