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.

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.

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.

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.

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.

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.

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

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.

Balancing your glaze

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 matt 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 matt glaze results, one that looks matt but is prone to discoloration.

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 coming out with a grainy surface,

If you have a problem with glazes coming out with a grainy surface, you may be applying them too thin. The best way to correct this problem is to warm piece slightly and apply another coat, then re-fire to proper cone.

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.

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.

Glaze Settling: remedy

If a glaze has settled out, but has not gone rock hard in the bottom of the container, you can add CMC or bentonite, if you happen to have it. But especially if you´re dealing with commercial glazes you probably don´t have that lying around. However, you can also use Epsom salts to suspend your glaze. Epsom salts can be readily purchased in most drug stores. First you need to create a saturated solution of Epsom salts by dissolving them in a cup of warm water until no more will dissolve. Then add this solution slowly and carefully to the glaze while continuously stirring the glaze. It should require less than approximately one teaspoon of Epsom salt solution per gallon of glaze. The quantity will depend on the severity of the problem. If a glaze has gotten too hard at the bottom to mix back up, first try my favorite glaze-stirring tool, a handheld kitchen stick blender. If that doesn´t work, drain all the liquid off, work on dissolving the solid into the Epsom salt / water mixture, then add the rest of the glaze liquid back in.

Acidic oxides

Acidic oxides are oxides displaying acidic properties in ceramic fusions. They are Silica and phosphorus oxide. A number of other oxides, which are mostly dioxides, display some acidic properties in ceramic fusions. However they also display amphoteric properties which make it difficult to assess the unity formulae in which they appear. Those with strong acidic properties are:
Boron oxide
Titanium oxide
Tim oxide
Zirconium oxide
Cerium oxide
Vanadium oxide
Germanium oxide
Those with slight acidic properties are:
Antimony oxide
Arsenic oxide
Praseodymium oxide
Two other oxides display acidic properties in the raw state but change their oxidation during firing to become alkaline in character. They are:
Manganese dioxide
Lead dioxide
Manganese dioxide becomes manganese monoxide at 1080c. Lead dioxide is part of the lead compound called red lead. It becomes lead monoxide at 600c.

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

Recipe: silver/gold clay paste

Lustre paste recipes: silver and golds
1. burnt umber 3
silver nitrate 1
+ vinegar

2. red clay 32
tin oxide 4
copper carb 10
silver nitrate 5
+ vinegar

Remove the glaze

If you want to remove the glaze from the bottom of a piece to avoid slippage from stilts during firing, or you plan to felt bottoms, try removing the excess glaze with a piece of window screen placed on a table. Many keep a piece tacked to the corner of their work table at all times, just for this purpose.

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.

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.

Take notes

Finally, remember to take notes while working with glazes. It´s very disappointing to discover a wonderful glaze combination but not remember what it was. Two glazes when layered can make colors quite different from either of the two glazes alone, so if you didn´t make a note, you may never know what you did!

Craters in your glaze

If you have craters in your glaze, they can be saved by putting glaze in the craters and refiring to one cone hotter.

Test tiles

You can make your own test tile chart for home use. I suggest test tiles be made and fired before glazing any piece with that glaze.
Simply cut rectangles approx. 4"X2", you can texture with lines carved into the clay, (This will give you an indication of the glaze flow). Bisque.
When applying your glaze, brush on in order 1 coat, 2 coats, 3 coats (this helps you gauge desired thickness).
Of course you can apply slips or underglazes to unbisqued tiles for further tests. I suggest using a variety of clays for each test, as the body can radically affect the glaze results.
Put holes in the corners of each tile, for hanging. Clearly mark the back of each tile eg C/W twe. (the clay body), Copper Red 1(Glaze used), the date can also be a handy reference to your notes.
Also keep detailed writen or computerised notes on all tiles. To the full recipe, add the firing details, description of the finished glaze and conclusion to these notes, you will find them invaluable in the future, so keep them safe.
A great Book for the experimentation of glazes is:
GLAZES And Glazing Techniques by Greg Daly. Kangaroo Press. ISBN:0-86417-502-7

Peeling

You may find that glazes are peeling from your ware. This is usually caused by too heavy and application of glaze over underglazes or one-strokes

Black, semi glossy oilspot

Oxidation:


Black, semi glossy oilspot

Rather thick or it will be no spots. 1260-1280oC with one hour at the top temperature.
Albany slip (the real thing) 70,74
petalite 16,08
ochre 8,36
red ferric oxide 4,82

Applying Mother of Pearl

Most pearl lustres are applied in a criss-cross fashion, using three coats, eg one coat down one coat accross and one on a 45% angle.

Clear to Milky Crackle

Clear to Milky Crackle: Cone 4 - 6 Oxidation
Lithium Carbonate (Toxic!) 25.0
Gerstly Borate 25.0
Zinc Oxide (calcined) 5.0
Calcium Flouride 5.0
Silica 25.0
Bentonite 2.0
Not suitable for tableware!

Reds

Reds in glazes and underglazes are the hardest to accomplish and even the most experienced tend to purchase reds as they are so unreliable. Even the bought reds come up a lot better if put over a golden yellow underglaze. My advice is to buy these colours.

Copper Green

Copper Green
Cone 03
Oxidation
Kaolin 14
Dolomite 8
Potash Feldspar 64
Whiting 16
Tin Oxide 4
Copper Oxide 1.2

Clear Gloss 3

Clear Gloss: Cone 6 Oxidation
Nephelene Syenite 46.2
Gerstly Borate28.0
Silica 20.4
Kaolin 5.4
Bentonite 1.0

Bubbled glaze Description

Bubbled glaze can be caused by immature bisque, too heavy an application of glaze or by not firing the piece hot enough. Correct this by firing the piece to one cone hotter.

Stoneware Crude glazes

We can create crude glazes from single materials. Borax can be dusted on a piece and fired to make a runny low-fire glaze. Galena (raw lead ore) was often used in the same way on folk pottery. Work fired in wood burning kilns is often glazed by the wood ash that flies along with the draft of the kiln. Depending on the build up of ash during the firing this creates from a light sheen to a thick runny glaze on the shoulder of the ware. Salt or sodium bicarbonate (baking soda) can be used to create vapor glazes. The salt or soda is thrown or sprayed into the kiln at peak temperature to create sodium vapor. The vapor condenses on the ware and combines with the clay to create a glaze. Sufficiently low temperature clay can be mixed into a slip and used a glaze on high fired pottery. Also, some feldspars melt at low enough temperatures to make crude cone 10 glazes. Some of these techniques are still used by potters who admire their simplicity and natural earthy aesthetic.
All of the above methods of glazing have inherent difficulties. Dusted on glazes can only be used on nearly horizontal surfaces. Wood firing is time consuming and labor intensive, and except in certain areas of the kiln, the deposit of fly ash is incidental--it makes beautiful accents, but it hardly qualifies as a functional glaze. Vapor glazing also glazes the entire interior of the kiln and all the props used to support the ware which considerably shortens their lives. Most of these glazes have serious flaws from a functional stand point. They make be crackled, excessively runny, or present problems in applying the glaze to the ware. The glazes that we´ll be using are combinations of raw materials carefully combined to avoid these problems. They are applied as liquids to bisqueware and fired to cone 10 to melt them.

Feldspar

Typically when formulating a glaze we´ll start with a feldspar, add a flux to lower the melting point, add clay to help keep the raw glaze in suspension and to help make the glaze adhere to the bisqueware, and add flint to keep the glaze from crazing (crackling). Colorants and opacifiers are added after the base glaze has been tested. Creating new glazes takes long hours of mixing small batches and firing them on test tiles. The choice of ingredients and proportions can be guided by calculations or by using rules of thumb and trial and error. Usually it´s a little bit of both.

Application

During the formulation of red glazes, there are certain minerals hard for manufacturers to eliminate. One of these is manganese which produces a black speck in the finished piece.
Black specks in red glazes can also be caused by dirty bisque so be sure to inspect pieces before applying reds.
To get the best results with reds, you should apply glazes of the same family on bisque.
Red glazes should not be thinned when applying three coats of even coverage. Some teachers even recommend four to five coats.
Most of the problems with red glazes occur during the firing process.
The recommended bisque you should use for red glazes is that which has been fired to cone 04 or 05.
You should not fire raw clay bodies with reds.

Basic glaze additions

Plus a glaze may include one or more additives:
1. Opacifiers – to make the glaze opaque instead of transparent. Examples: tin oxide, zirconium or Zircopax, titanium, zinc
2. Suspenders – to keep the glaze in suspension instead of settling out. Examples: bentonite
3. Colorants – to provide various colors. Examples: cobalt oxide, copper oxide.

Transparent Flowing Glaze

Transparent Flowing Glaze
Cone 04
Oxidation
Lead Bisilicate (Toxic!) 76.5
Kaolin 8.0
Nephelene Syenite 15.5
Comment: variations can be achieved by adding small amounts of oxides and carbonates ( 2-5%).
Not suitable for tableware!

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.

Waxing: Lids

We use wax to keep lids from becoming glazed to jars. Stoneware can distort in firing, so we usually fire lidded containers with their lids on. Otherwise, the jar opening might go out of round, and the lid may not fit well. Wax all the points where the lid and jar come into contact. It´s a good idea to run the wax about 1/8" back from the line where they meet both inside and outside the pot in case the glaze runs.

Talc White

Talc White
Cone 9
Oxidation or Reduction
Potash Feldspar 38.5
Silica 27.0
Whiting 16.3
Kaolin 2.9
Bentonite 3.0
Talc 12.5

Recipe: Jade green ash glaze

Vert jade cendré (Jade green ash glaze)
Cone 04
Hardwood ash(washed) 36%
Custer spar 14.5%
Frit #3134 23%
E.P.kaolin 14.5%
Lithium carbonate 12%
Bentonite 2%
Ultrox 15.5%
Black copper oxide 3.5%

Bleu de Ginette (Ginette´s blue)

Bleu de Ginette (Ginette´s blue)
Cone 04
Hardwood ash(washed)35%
Custer spar 14%
Frit #3134 25%
E.P.kaolin 14%
Lithium carbonate 12%
Bentonite 2%
Ultrox 15%
Cobalt oxide 5%

Glossy yellowish with blue crystals

Crystal glazes: Glossy yellowish with blue crystals
One of my most popular crystal glazes based on zinc and lithium. Too thick it will run a lot, but it can be controlled very exactly after a few tests. Always spray the glaze thinner near the bottom of the pot. 1260oC with 1/2 to one hour at the top temperature. Does not need a slow cooling. You can also try other combinations of coloring oxides.
potash feldspar NR 27,60
quarts (flint) 32,20
dolomite 3,48
zinc oxide 18,70
barium carbonate 4,44
china clay 2,75
lithium carbonate 6,82
rutile 4,01
cobalt oxide 1,06

Types of test tiles: Round textured tiles

Using cookie cutters make round tiles with a decent sized hole a little in from one edge. Leave one half smooth & flat and use any method you like to create a raised pattern of some sort on the other half, so you get an idea of what the glaze would look like on an incised or impressed surface.

Recipe: Semi matt dark blue

Crystal glazes: Semi matt dark blue
A glaze with zinc. You must not apply it too thick. 1260-1280oC with one hour at the top temperature. Does not need a slow cooling. Small or no crystals.
potash feldspar NR 65,90
dolomite 16,15
zinc oxide 17,95
red ferric oxide 5,00
cobalt oxide 2,00

Tenmoku Red

Tenmoku Red
Cone 03
Oxidation
Potash Feldspar 39
Whiting 15
Ball Clay 12
Silica 200# 25
Red Iron Oxide 9
*See Disclaimer*

Mixing glaze tests: Let them sit

With glaze test batches, as with full batches, it is useful to let the glaze sit for 2 days to fully absorb, then re-mix.

Storing Tests: Boxing the duds

Get a large box to keep those you will never want to use again! Never throw glaze tests out... You THINK you will always remember the duds, but it is surprising how fast you forget the results even if you remember testing a certain glaze.

Copper Red #2

Copper Red
Cone 9 - 10
Reduction
Nepheline Syenite 206.97
Colemite 46.35
Whiting 40.20
Copper Oxide 1.45
Tin Oxide 3.75
Silicon Carbide 1.13

Thanks to Giordano Andrew Voeks
of Hawaii for this glaze.

Satin Mottled Eucalyptus

Helens Satin Mottled Eucalyptus: Cone 5 Neutral Gas Atmosphere. Comment: Results in muddy color in electic kiln. Not suitable for tableware!
Nephelene Syenite 40
Whiting 25
Ball Clay 25
Lithium Carbonate 5
Silica 5
Copper Carbonate 2

Mottled brown ash glaze

Edouard´s Brun veiné cendré (Mottled brown ash glaze) Cone 4. Thank you to Edouard Bastarache for supplying this glaze recipie.
Nepheline/Syenite 25%
Hardwood ash(washed) 20%
Silica 20%
Ball clay 5%
Gerstley borate 30%
Bentonite 2%
Ultrox 15%
Cobalt oxide 5%

Waxing

We need to wax the bottom of the piece. Any part of the piece that will come within 1/4" of the kiln shelf should not have any glaze on it. This is called dry footing. Melted glaze acts like a glue when it comes between two surfaces. If there is any glaze on the bottom of your piece, it will become glued to the kiln shelf in the firing. At worst it will have to be removed with a hammer and chisel, and the kiln shelf will be ruined.

Metallic oxides

The color that a metallic oxide gives to a glaze depends a great deal on the composition of the glaze, the firing temperature, and the atmosphere in which it´s fired. Many of the colorants used to make bright colored glazes at low temperatures vaporize well before cone 10, so they can´t be used in high fired glazes. The colors of cone 10 glazes are mostly earthy--keep this in mind as you design your pieces. Very literal or painterly decorations that require a lot of detail and color contrast are hard to create on stoneware. Cone 10 glazes are quite beautiful--the firing can add accents that range from striking to subtle. Be patient as you learn to use them to their full potential.

Mixing: adding a marble to a jar of stain

You know how you get those spray can of household items with the bead inside to help mix them when you shake the can? You can do the same thing by adding a marble to a jar of colour before you mix it and it will help you complete the job.

Semi matt golden yellow

Semi matt golden yellow

Very intensive golden yellow. More red when thin, glossier when thicker. 1270oC with one hour at top temperature. Safe glaze.

potash feldspar NR 64,35
whiting 18,93
china clay 3,15
Albany slip 5,68
rutile 7,89
red ferric oxide 6,31

Salt and pepper shaker holes

It is often difficult to keep salt and pepper shaker holes in the top from filling in with glaze during the firing. Next time insert short pieces of toothpick in each hole and put them in the kiln that way. The wooden toothpick will burn out during the firing but will help to keep holes clear of glaze.

To avoid pitting and pinholes

To avoid pitting and pinholes in your glaze, be sure that your greenware is free of dust before applying glaze. A damp sponge will help to do the job.

Wise use of your metallics and lustres.

Never dip your brush diretly into a container of metallic or lustre to begin application. Always pour a small amount of colour into an alcohol cleaned container and load brushes from this. These materials are expensive and you may have a contaminated brush and ruin an entire supply rather than just a bit in a dish.

Types of test tiles: Extruded "T"

“T" shaped tiles made from an extruder. Make one side of the leg of the T smooth, the other side a texture. Do the three dips with the leg of the T. Lay it upside down (on the top part of the T) to fire, which will help to catch runny glaze, or if you glaze the whole inside L also give you an idea of what the glaze acts like on a flat surface.

Clear Gloss 3

Clear Gloss
Cone 9 - 10
Oxidation or Reduction
Potash Feldspar 23.0
Whiting 11.0
Talc 15.0
Silica 13.0
Bone Ash 4.0
Kaolin 15.0
Ball Clay 13.0

Comment: good for tableware.

Recipe: Aqua Blue Dry Glaze

Aqua Blue Dry Glaze
Cone 2 - 4
Oxidation
Nephelene Syenite 40.0
Barium Carbonate (Toxic!) 30.0
Ball Clay 15.0
Zinc Oxide 5.0
Black Copper Oxide 4.0
Comment: Fast cooling helps preserve color.

Rusty Red Black Fire Glaze

Salvatoris Rusty Red Black Fire Glaze
Copper Carbonate 60.0
Borax 40
Sodium Bicarbonate 40
Cobalt Carbonate 5.0

Comments:
Bisquefire work to 1100o C
Mix glaze same day as firing
Apply glaze thickly
Dribble glaze on thickly for effects

Clear Crackle

Clear Crackle: Cone 6 Oxidation
Volcanic Ash 52.5
Ferro Frit 3134 28.0
Kaolin 5.3
Kaolin (calcined) 4.0
Bentonite 2.0

Pouring glazes

Pieces that are too large to fit in the glaze bucket can be poured. Hold the piece over a large bowl and pour glaze onto the pot. Try to get the glaze layer even by pouring steadily and rotating the piece. Again, any overlapping areas will usually show, so you can use this decoratively. For cylindrical forms or mugs, it´s usually best to glaze the inside by pouring. Pour the glaze into the pot and slowly rotate it as you pour it out. The outside then can be glazed after the inside dries.

Blistering

can happen with glazes that boil a lot before maturing in the kiln. If the kiln isn´t held at the top temperature long enough, bubbles that form in the boiling stage don´t get a chance to heal
completely. This usually leaves little smoothed out craters in the glaze.

Glazingsalt and pepper shakers

The inside of salt and pepper shakers should be glazed too. If you have trouble getting the glaze inside, use a squeeze bottle and force it in. You may also thin glaze with water to help with the job of pouring it in. Be sure to use a toothpick or tool to clear holes in top

Black specks

Black specks in the ware are usually caused by organic materials not completely burned out in the bisque firing. They work their way to the surface during a glaze firing

Dry between coats

Before applying second and third coats of colour, be sure that previous coats have dried completely.

Applying Matte glazes

Because Matte glazes do not flow during the firing process, it is necessary to not only necessary to apply them as evenly as possible, but is is also a good idea to rub each coat of colour lightly with your fingertips to even out brush strokes and eliminate any glaze pile up.

Greyed red family glazes

Greyed red family glazes can be caused by not applying enough colour, most manufacturers recommend 3-5 coats.

Making a basic glaze

To make a glaze, we need to find sources of Silica, Alumina and a flux which are convenient to use, in a form that does not dissolve in water. 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 that 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 do not reach the temperatures required. Therefore, we need to add fluxes, which lower the melting point.

To remove glaze from fired pieces

To remove glaze from the bottom of pieces that you want to dryfoot, mount a piece of sandpaper on a board or table top and simply rub off the glaze in that area.

Mixing glaze tests: Knowing your level

Many people use old blenders or stick blenders for mixing test batches. They mark off with a magic marker where enough water for a 100g test comes, so they can just put in the water and add ingredients as they are weighed out. (Tip: Use a piece of masking tape until you are sure enough to draw your line with a magic marker.) Another reason to mark where a 100g or a 200g batch of wet glaze comes, is so you can can add that much base glaze before adding colorants or other ingredients.

remove mistakes when using gold

It is possible to remove mistakes when using gold or lustres by using a ‘gold eraser'. It looks like a normal eraser but is chemically formulated to do the job as well as containing an abrasive.

Shivering Remedy

Shivering
Shivering occurs when a glaze contracts lees than the clay body. Parts of the glaze crack and move against each other lifting off from the clay surface. This can be so bad that pieces of glaze will actually jump off the surface.
Remedies:
· Reduce silica in the clay body
· Reduce silica in the glaze
· Reduce alumina in the glaze

Tomato Red

Tomato Red
Cone 03
Oxidation
Potash Feldspar 42.52
Slica 200# 18.9
Kaolin 6.3
Magnesium Carbonate (Light) 5.51
Whiting 6.3
Bone Ash (Synthetic) 10.24
Red Iron Oxide 10.24
*See Disclaimer*

Basics of a glaze

Every glaze is made of the following 3 materials:
1. Silica – Creates glass. Examples: quartz, flint, pure silica
2. Alumina – Stiffens the glaze so it doesn't slide off the clay. Examples: clay (kaolin, ball clay, or fire clay), alumina hydrate
3. Flux – Causes the glaze to melt at a low enough temperature to be used in ceramics. Examples: feldspar, whiting

Cream Apricot

Cream Apricot
Cone 03
Oxidation
Potash Feldspar 30
Whiting 30
Kaolin 30
Titanium 10
*See Disclaimer*

Understanding %´s

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. We need to understand why!

Leadfree glaze testing

Using lead free glazes:
Make test firings of the body and glaze to their recommended cone number, first the unglazed body, then the glazed bisque.
Use witness cones placed near the ware to be sure the proper cone number was reached. Differences may exist between the Kiln-Sitter and a witness cone or from the top to the bottom of the kiln. Firing with a controller to a cone number or a temperature may not be adequate.

Using slips/oxide washes with glazes

Thin slips and oxide washes can be used to decorate a piece by applying them directly to the bisque or on top of a glaze. Clear, celedon, and some light opaque glazes can be used over the colorants. Be careful not to get oxides and slips on too thick--the application should be more like water colors than house paint. The colorants are mostly quite strong, and if they are
thick the overlying glaze is likely to crawl. Decorations can be brushed, stamped with foam stamps or sponges, spattered, sponged into textures, silk screened...