What are 3 rules when working with glaze in ceramics?

Do not interchange eating and glazing utensils. Scrub your hands thoroughly after glazing. Use a Ceramic dust filter mask that fits well when mixing, spraying, or sanding glazes .

How do I know what glaze to use?

You'll need to know what you are using your final piece for, how you are going to fire it, what type of heat you are going to need and what type of finish you are going to want . You'll also need to consider how many pieces you are looking to make so that the glaze can be applied easily.

What is one thing you need to remember when glazing your pottery?

To start, apply glaze to the tip of a soft brush and then paint your pottery however you want! It's important to remember to only pick up a small amount of glaze each time you need more . If your brush is overloaded, it won't give you the texture that you're looking for as you paint.

What are the levels of glaze?

By knowing which level to view a glaze from you are much better equipped to understand and control it. The levels are process, recipe, material, oxide .

What is the golden rule of ceramics?

Always handle your project with two hands . In other words: BE CAREFUL, it's your hard work! NEVER handle another person's work, even if it looks cool.

Do you glaze inside or outside first pottery?

You will want to glaze the inside of your pottery first . If you glaze the outside first, your chances of leaving marks and messing up the outside of your piece will go way up. To glaze the inside of a piece, pour the glaze into the internal area and rotate the piece to cover the entire interior.

How to glaze ceramics for beginners?

The general process of glazing ceramics is by mixing your glazes, applying the glaze to bisque-ware, letting it dry, then finally loading it into the kiln for the glaze firing. The kiln is slowly brought up to the appropriate temperature for the silica in the glaze to melt, then slowly cooled again.

How to choose pottery glazes?

To guarantee the success of your project, it is essential that the recommended firing temperature for the glaze is compatible with the clay you have chosen . In general, it is essential to use low temperature glazes with low temperature clays and high temperature glazes with high temperature clays.

How is underglaze different from glaze?

A glaze is a paint composed by a bunch of chemicals that, when added to a bisqued piece, it will make that glass shiny cover. An underglaze is a paint composed by a bunch of chemicals that you can add to greenware or bisqued pieces to add color but it will not add the glass part .

What is the 3 pull rule ceramics?

The 3-pull rule is simple: the majority of your form should be pulled up in just 3 pulls . This does not include shaping, which requires a separate effort. Begin by centering and opening the clay, then as soon as you start pulling up, aim to move as much clay as possible in the first three pulls.

What are 3 ceramic techniques used in pottery making?

The most common handbuilding techniques are pinch pottery, coil building, and slab building .

Understanding Pottery Glazes (2024)

GLAZE RECIPES

Glaze recipes are typically expressed by listing each raw material and its % by weight. The percentages add up to 100 Usually colorants and sometimes other additives (such as bentonite for suspension) are not included in the 100%, they are added on afterward.

EXAMPLE: CONE 6 CLEAR BASE GLAZE

Wallastonite 10%
FRIT 3134 30%
Kaolin 25%
Flint 15%
F-4 Feldspar 20%
Total 100%
Add 4% cobalt oxide for a deep blue

To mix this glaze, you take the total number of grams of dry material you are making, multiply by the % to get the grams of each material to add.

EXAMPLE: TO MAKE 1000G OF GLAZE

Wallastonite = 10/100*1000=100 grams
FRIT 3134=30/100*1000=300 grams
Kaolin = 25/100*1000=250 grams
Flint = 15/100*1000 = 150 grams
F-4 Feldspar = 20/100*1000 = 200 grams
To double check, add up all the grams and make sure they equal 1000.
Then add 4/100*1000 = 40 grams cobalt oxide

This is as far as many people go. They make the glaze, test it, and often are unhappy with the results. So let’s go further and understand why.

GLACE COMPOSITION

Every glaze is made of the following 3 materials:

Silica – Creates glass. Examples: quartz, flint, pure silica
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Alumina – Stiffens the glaze so it doesn’t slide off the clay. Examples: clay (kaolin, ball clay, or fire clay), alumina hydrate
Flux – Causes the glaze to melt at a low enough temperature to be used in ceramics. Examples: feldspar, whiting

Plus a glaze may include one or more additives:

Opacifiers – to make the glaze opaque instead of transparent. Examples: tin oxide, zirconium or Zircopax, titanium, zinc
Suspenders – to keep the glaze in suspension instead of settling out. Examples: bentonite
Colorants – to provide various colors. Examples: cobalt oxide, copper oxide

To make a glaze, we need to find sources of each of the above which are convenient to use, in a form that does not dissolve in water. As we saw in the last tip (#34), glaze materials can be broken down into their chemical compositions, and from there we can see what the effect of each material will be.

To provide silica in the glaze, we need a material than contains: SiO2=Silicon Dioxide, comes from flint, quartz and pure silica

To provide alumina in the glaze, we need a material that contains: Al2O3=Aluminum Oxide, comes from feldspar, cryolite, clay

FLUXES

Silica and alumina would create a glaze if fired hot enough. However, ceramic kilns are do not reach the temperatures required. Therefore, we need to add fluxes, which lower the melting point.

To provide flux in the glaze, we need a material that contains one or more of the following:

Li2O=Lithium Oxide, comes from Lithium carbonate, Petalite, Spudomene
K2O=Potassium Oxide; comes from Potash Feldspar, frit
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CaO=Calcium Oxide, comes from whiting, limestone, wollastonite (also provides SiO2), wood ash, bone ash, dolomite (also provides MgO)
MgO=Magnesium Oxide, comes from magnesium carbonate, dolomite (also provides CaO), talc
ZnO=Zinc Oxide, comes from zinc oxide
SrO=Strontium Oxide, comes from strontium carbonate
BaO=Barium Oxide, comes from barium carbonate
PbO=Lead Oxide (not used much due to toxicity)
Na2O=Sodium Oxide, comes from feldspar, FRIT, cryolite, nepheline syenite
TiO2=Titanium Dioxide, comes from pure titania, rutile
ZrO2=Zirconium Dioxide, comes from zirconium dioxide, zircopax, zirconium silicate
SnO2=Tin Oxide, comes from stannic oxide (SnO2 white), stannous oxide (SnO black)
B2O3=Boric Acid or Boron, comes from Colmanite, Gerstley Borate, CadyCal. Effective for lowering the melting point of a glaze.

Now don’t panic! This isn’t chemistry class, and you don’t have to memorize this list! But if you’ve worked with glaze recipes at all, you probably recognize many of these terms, and can start to understand what they are used for.

You can take any glaze recipe, and break each ingredient down into it’s chemical composition as shown last week. An easy way to do this is by looking up the material in the DigitalFire database.http://www.ceramicsearch.com/material/

Once you have the chemical composition of the ingredient, you can see what it contributes to the glaze. For example, is it primarily contributing silica, alumina, or a flux? Often a single ingredient contributes a combination of these. For example, Feldspar is primarily a combination of alumina and silica. And so is clay.

Glazes need a balance of the 3 main ingredients: Silica, Alumina and Flux.

Too much flux causes a glaze to run, and tends to create variable texture on the surface. The texture may vary from shiny, where the glass is balanced, to matte where the excessive flux oxides may form visible, possibly lumpy, crystals.
Too much silica will create a stiff, white and densely opaque glass with an uneven surface. It will be glossy in spots, but the suspended silica can form crystals producing harsh dry surfaces. Too much silica will also inhibit the melting of a glaze, and the resulting surface will be roughly textured like sandpaper.
Too much alumina causes a glaze to stiffen and tend towards opacity, again with a textured surface where it is dry in spots. Glazes will often have pinhole defects. Too much alumina can inhibit the melting of the glaze to the extent that a poor quality matte glaze results, one that looks matte but is prone to discoloration.

SO HOW DOES THIS HELP YOU?

By understanding what different materials do, you can adjust a glaze recipe to change its characteristics or fix its problems. For example, you can make a transparent glaze into a matt glaze. You can stop crawling, pinholing, or crazing. You can lower the melting temperature of a glaze. You can make a substitution if you run out of an ingredient. This ability completely changes the way you work with glazes.

UNITY FORMULA AND GLAZE CALCULATION PROGRAMS

You may have heard of something called a unity formula, or Seger formula. This is a way of expressing a glaze by the ratios of its oxides rather than % of raw materials. It is one of the primary methods used in analyzing glazes. I’m going to skip the detailed math. But the concept is that using information about each raw material, you create a ratio of the amount of flux to the amount of silica and alumina. These ratios can then be compared to ones which have been determined to work in a certain way at a specific temperature.

These calculations are very detailed and take a long time to do by hand. And because there are many factors that all interact, it would take a long time to learn each material and the effect it has on a glaze. So potters have created a variety of computer programs that simplify the analysis and formulation of glazes.

You can learn more by taking the self paced on-line tutorial called Glaze Teach.http://www.matrix2000.co.nz/GlazeTeach/Index.htmThe writers of this tutorial offer a glaze calculation software program called Matrix.

Or visit DigitalFirehttp://www.digitalfire.com, a website that explains glaze chemistry and sells a software program called Insight to help automate this glaze analysis process.

So, if this whole thing looks interesting to you, you will probably want to explore the world of glaze chemistry more. On the other hand, if it makes your eyes glaze over (no pun intended), you probably should stick to commercial glazes or trial and error. Happy glazing!

(note, the numbers in the above chemical formulas would properly be expressed as subscripts)

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