Welcome to Ceramics Tips

Reglazing fired pieces

To re-glaze a fired piece you need to do one of the following:
Spray the piece with spray starch, let dry, then reglaze.
Spray the piece with sticky hairspray (usually the cheapest you can find), dry, reglaze.
Heat the piece first, with a heat gun or in the oven or kiln, then apply glaze, (my favourite).
Brush white (Elmer´s) glue on, let dry, reglaze.
Microwave the piece for 30 seconds. (Some potters say this makes a huge difference, and the piece doesn´t need to actually get or stay hot)
Add some suspension agent to the glaze (CMC gum or Bentonite.)
Add some detergent / shampoo to the glaze (baby shampoo is good because it doesn´t foam)
To improve your odds further, wash the pot first with ammonia or detergent, wearing rubber gloves, and don´t touch it. The oils from your fingers can prevent glaze from sticking.
And... Don´t use too much of anything. If you get the coating too thick, you may prevent adhesion instead of encouraging it.

Olive Matt/Soft Red

Helens Olive Matt/Soft Red
Cone 6-9
Reduction or Oxidation
Nephelene Syenite 75
Whiting 10
Dolomite 10
Bentonite 4
Silica 5
Copper Oxide 2

Comments: Cone 5-6 (electric kiln, oxidation) gives Olive Matt; Cone 9 (electric kiln, oxidation) gives Green/Orange Gloss; Cone 9 (gas kiln reduction) gives Soft Red Gloss.

Mixing a glaze

Mixing a glaze:
Following the recipe, weigh out all the ingredients. Place all the glaze powder in a container at least twice its volume. Add approx. 100ml of water to every 100g of solids. Leave for 30 minutes to allow the glaze powders to absorb the water. This will break down any lumps and make for easier mixing. The glaze is now in slop form. Mix it thoroughly with a lawn brush, breaking up any large lumps as you go. Pass the glaze through an 80 mesh sieve into its permanent container, and use the lawn brush to push coarse material through the sieve. This ensures that all the ingredients are of a small particle size and will disperse. Stir the glaze to check its consistency. It should be like single cream, depending of course on your method of application.

Clear Satin Matt

Clear Satin Matt: Cone 4 - 7 Oxidation
Ferro Frit 4508 50.0
Potash Feldspar 20.0
Ball Clay 20.0
Magnesium Carbonate 10.0

Glaze Selection

As we become better at making beautiful forms we don't necessarily become better at achieving great glaze results. It seems so unfair! If you are serious about achieving great results your first step is to begin your own glaze journal today. It's important to do many different things right before you can be successful at glazing. First, consider what textures and colors you want the glaze to contribute to your finished form. Many art centers and community labs have test tiles you can observe before you commit to glazing with them. (If you are at a home studio, you will want to create your own test tile pattern with some of your favorite glazes.) We recommend you test one coat or two to see if it runs or changes colors when applied thicker. Also, test glazes on different clay bodies. If your facility has tiles, they probably indicate which glazes are stable and which glazes run. Glazes that run are not suitable for the outside of a piece. A glaze that runs can run off the pot and onto the kiln shelf making a huge mess. The same glaze can look very different on various clay bodies. Also, it may look different when applied thin vs. thick. An example is a copper red glaze called Oxblood, it´s white when applied thin, red when applied thick - quite a difference.
The next step is choosing a suitable glaze for your clay body.

Coat marker

A lead pencil is a handy tool for keeping track of the number of coats of glaze you have on a piece. You can write which step you are on over the glaze and the marks will fire out.

Glazes

Ceramic glazes are a fascinating combination of chemistry and art and can be dangerous if not handled with care and experience. There are so may iterations of ceramic glazes that you can truly achieve any color, patina or effect that you want but take care - using metals, chemicals and other components can be dangerous - especially in your home and without proper containment or protective gear. Still, have fun finding your signature glaze and making your ceramic piece stand out from the rest.

Refire a piece

If you find it necessary to glaze an already fired piece again, place it in your warm kitchen oven just long enough to get the piece slightly warm. Take the piece out and glaze immediately. The glaze will dry instantly and not slide off the fired surface.

Layering glazes

Some of the most interesting effects can be obtained by layering glazes. Try dipping an already glazed pot part of the way into another glaze. This greatly increases the chance of the glaze running, so don´t try to doubling up the glaze all the way to the bottom of the pot. The best results usually come from trying a matt glaze over a gloss glaze. If the first layer of glaze isn´t good and dry before applying the second, there is a good chance the glaze will crawl. A piece of bisque can only absorb so much water before it becomes saturated, so let it dry first. Anytime you notice the glaze cracking or peeling, it´s probably too thick, so you´re best off washing all the glaze off and starting over. Keep in mind that the glaze that falls off your piece can land on somebody else´s and ruin it also.

Glaze Settling

Have you ever had a glaze that kept settling to the bottom of your bucket? This is a common problem and may result in firing problems. When a glaze settles out, some of the heavier components of the glaze settle to the bottom of the container. If you try to use this glaze without thoroughly remixing you will be applying a glaze with key ingredients missing. A glaze stays in suspension due to the presence of various types of clays, such as bentonite, and/or gums, such as CMC. One common cause of settling out is the addition of too much water to the glaze, which dilutes the effect of the suspending agents and allows some of the glaze ingredients to settle out. Another possibility is the growth of bacteria which will consume an organic gum, such as CMC, and will lead to loss of suspension. To prevent bacteria growth do no return used glaze, which has been poured out of the original container, back into the original container. Also do not introduce possibly contaminated objects, such as brushes, into the original container. Storing glaze in a hot or sunny environment may also encourage bacteria growth. Freezing can also destroy the action of CMC. And glaze ingredients such as frits, nepheline syenite, soda feldspar and other slightly soluble materials slowly release sodium ions which can deactivate the suspension agent, making it ineffective.

What is a Flux?

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
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.
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 its chemical composition as shown last week. An easy way to do this is by looking up the material in the DigitalFire database. DigitalFire database
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.

Pouring

Pouring is a technique which may be used if a work is too large to dip, or if there is just not enough glaze available. The ceramic object is held in one hand and glaze is poured over it as evenly as possible, until the whole surface is covered. With this method, overlapping is inevitable. If this is an issue with the glaze used, edges may be smothed over by rubbing with a finger. Hint: do not rub glazes with unprotected fingers if they contain toxic ingredients like lead, manganese or even copper! (Try rubber gloves.)

Satin glaze

Since a satin glaze is one with a soft sheen which moves only slightly during firing, you may be able to create your own by applying alternate coats of transparent matte and a coloured gloss glaze.

Decorating the yard with ceramics

Decorating the yard with ceramic pieces is always a lot of fun, but many forget to prepare the inside of pieces. Be sure to glaze the inside of all your pieces as well as staining outside. This will help to protect the piece from moisture and make the decoration on the outside last a lot longer. If you do not protect the inside moisture can get into the bisque and push the decoration off the outside, usually in the form of chipping.

Using sand

For a little different technique you can use sand in combination with your glazes. It should be of a washed, fine grain and can produce a texture if applied to a piece with glaze.

Blistering

Blistering
When a glaze has a ´bubbled´, lava-like surface, this is called blistering. Some so-called ´lava glazes´ are specifically formulated to blister. Normally this effect occurs when gases released from the glaze become trapped in the glaze matrix before they can escape and the glaze smooth over. This can be due to undefiring or overfiring.
Remedies:
· Fire the kiln slower
· Reduce kiln atmosphere less

Essential components

The essential components of a glaze are silica, fluxes, and alumina. Silica is the basis of most glasses. The melting point of silica is over 3000oF, so we add fluxes to lower the melting point of the glaze. Alumina is needed to keep the glaze from becoming too fluid when it melts. Feldspar provides all three of these compounds and is the main ingredient in most cone 10 glazes.

Storing Tests: Boards

Hammer rows of nails into a large board and hang the tiles on them. If you use long nails, each one will take several tiles. You can sort them by color, texture, etc.