Types of Ceramic Glazes: A Complete Overview | Pottery Guide

Ceramic glaze is not paint. It is a glass coating that fuses to the clay body at temperatures above 1,800°F (982°C) through a permanent chemical bond.

Understanding the different types of ceramic glazes determines whether your pottery is food-safe, decorative, durable, or destined to fail in the kiln. This guide covers low-fire, mid-fire, high-fire, gloss, matte, satin, crystalline, ash, shino, celadon, tenmoku, raku, salt, soda, and luster glazes: with firing temperatures, clay body compatibility, kiln requirements, and food safety status for each type.

What Are Ceramic Glazes?

Ceramic glaze is a thin glass layer that melts and fuses to the clay body surface during kiln firing. The glaze seals the porous clay, adds color, and creates a durable, often food-safe surface that cannot be achieved with clay alone.

According to Daniel Rhodes in Clay and Glazes for the Potter (first published 1957, updated through multiple editions), a glaze consists of three essential components: silica (the glass former), alumina (the stabilizer that prevents the glaze from running off the pot), and flux materials that lower the melting point to a specific firing range.

A glaze is not a paint or a stain. Paint sits on a surface. Glaze becomes part of the ceramic body at the molecular level during firing.

This chemical bond is what makes glazed pottery durable enough to hold boiling water, survive the dishwasher, and last for centuries in archaeological sites. The type of glaze you choose dictates every downstream decision: kiln temperature, clay body selection, firing atmosphere, and food safety status.

How Are Ceramic Glazes Categorized by Firing Temperature?

Ceramic glazes divide into three primary temperature categories: low-fire (cone 06 to 04, 1,828°F to 1,940°F / 998°C to 1,060°C), mid-fire (cone 5 to 6, 2,167°F to 2,232°F / 1,186°C to 1,222°C), and high-fire (cone 9 to 10, 2,300°F to 2,381°F / 1,260°C to 1,305°C). The firing temperature determines which clay bodies work with the glaze and whether the resulting surface is porous or fully vitrified.

Tony Hansen’s Digitalfire reference library documents that each temperature range requires a fundamentally different flux system to achieve full glaze melt. Low-fire glazes rely on boron-based frits and lead compounds (in older formulations). Mid-fire glazes use calcium, magnesium, and zinc as primary fluxes. High-fire glazes depend on feldspars, particularly potash and soda feldspars, which melt only above cone 9. Choosing the wrong temperature category means the glaze either never melts or runs off the pot entirely.

Low-Fire Glazes: Cone 06 to 04 (1,828°F to 1,940°F / 998°C to 1,060°C)

Low-fire glazes mature between cone 06 and cone 04. These glazes work exclusively with earthenware clay bodies, which have absorption rates above 3% even after proper firing and are never fully vitrified.

The mechanism that makes low-fire glazes work at these lower temperatures is the use of boron-based frits: pre-melted glass materials that act as powerful fluxes. Ferro Frit 3124 and Ferro Frit 3134 are the industry standards for low-fire clear and colored glazes.

This flux chemistry only functions between cone 06 and cone 04. If fired to cone 6, low-fire glaze becomes extremely fluid and runs off the pot, pooling on the kiln shelf and destroying both the shelf and the ware.

Key Specifications for Low-Fire Glazes:

• Firing range: cone 06 to 04 (1,828°F to 1,940°F / 998°C to 1,060°C)
• Compatible clay: earthenware only (absorption rate above 3% after firing)
• Kiln type: electric (oxidation only)
• Food safety: conditional (requires a well-formulated clear liner glaze over colored glazes; never food-safe on porous earthenware without an intact glaze layer)
• Color range: brightest and widest of all temperature ranges (lead-based formulations produce unmatched brilliance, though lead-free alternatives using boron frits are now standard)
• Cost: $12 to $18 per pint of commercial brushing glaze (Mayco, Duncan, Amaco low-fire lines)

Low-fire glazes dominate the commercial ceramics and hobby studio market. They produce the brightest colors at the lowest energy cost, making them the standard for decorative earthenware and children’s pottery programs.

For home studio potters working with a small electric kiln, low-fire glazes offer the easiest entry point. The lower temperature means faster firing cycles (6 to 8 hours for a bisque firing, 8 to 10 hours for glaze firing) and reduced electricity consumption. In plain terms: low-fire glazes are the easiest to use and produce bright colors, but the finished pot will absorb water and is not as strong as higher-fired ware.

Mid-Fire Glazes: Cone 5 to 6 (2,167°F to 2,232°F / 1,186°C to 1,222°C)

Mid-fire glazes are the studio pottery standard worldwide. At cone 6 (2,232°F / 1,222°C), stoneware and porcelain clay bodies achieve full vitrification with absorption rates under 1%, making them inherently food-safe even before glaze application.

According to John Hesselberth and Ron Roy in Mastering Cone 6 Glazes (2002), mid-fire glazes use calcium-magnesium-zinc flux systems that produce durable, chemically stable glass surfaces at temperatures achievable in any modern electric kiln. The calcium in the flux reacts with silica and alumina to form a calcium silicate glass matrix with 6 to 7 Mohs hardness: harder than most stainless steel utensils and fully dishwasher-safe.

This flux chemistry only activates between cone 5 and cone 6. Firing mid-fire glaze to cone 04 produces a dry, chalky, un-melted surface because the calcium fluxes have not reached their activation temperature. Firing to cone 10 over-fires the glaze, making it run and bubble.

Key Specifications for Mid-Fire Glazes:

• Firing range: cone 5 to 6 (2,167°F to 2,232°F / 1,186°C to 1,222°C)
• Compatible clay: stoneware and porcelain (absorption rate under 1% after firing)
• Kiln type: electric or gas
• Food safety: yes, when properly formulated and fired to full maturity on vitrified clay
• Color range: wide and sophisticated; iron-rich glazes produce warm browns, celadons, and tenmoku effects
• Cost: $15 to $22 per pint of commercial brushing glaze (Amaco Potters Choice, Coyote, Mayco Stoneware lines)

Mid-fire stoneware clay rated to cone 6 with 12% shrinkage and under 2% absorption is fully vitrified and safe for functional ware.

Mid-fire glazes offer the best balance of durability, color range, and firing accessibility. For most functional potters making mugs, bowls, and dinnerware, cone 6 is the logical and most practical choice.

High-Fire Glazes: Cone 9 to 10 (2,300°F to 2,381°F / 1,260°C to 1,305°C)

High-fire glazes mature between cone 9 and cone 10. These glazes are the traditional standard for functional stoneware and porcelain, producing surfaces with unmatched depth, subtlety, and mechanical durability.

The mechanism at cone 10 is the decomposition of feldspar minerals (primarily potash feldspar and soda feldspar) into a viscous glass melt. Custer feldspar and G-200 feldspar are the most common commercial sources, releasing potassium and sodium oxides that flux the silica-alumina matrix into a dense, chemically resistant glass.

This feldspar-driven flux system requires sustained temperatures above 2,300°F (1,260°C). Cone 10 glazes fired in an electric kiln to cone 6 remain completely un-melted: a powdery, chalky surface with zero glass formation because feldspars have not decomposed.

Key Specifications for High-Fire Glazes:

• Firing range: cone 9 to 10 (2,300°F to 2,381°F / 1,260°C to 1,305°C)
• Compatible clay: high-fire stoneware and true porcelain
• Kiln type: gas reduction or wood (electric kilns struggle with element longevity at these temperatures)
• Food safety: yes, the gold standard for durable functional ware
• Color range: narrower but deeper; reduction effects produce celadons, shinos, copper reds, and iron-rich tenmoku surfaces
• Cost: higher investment in kiln construction (gas kilns start at $2,000+) and fuel per firing ($25 to $50 for propane or natural gas per firing cycle)

High-fire stoneware clay for cone 10 reduction produces results that mid-fire glazes cannot replicate.

High-fire glazes produce the most durable ceramic surfaces available. For potters committed to reduction firing and traditional studio pottery aesthetics, cone 10 offers a depth of surface that mid-fire cannot match.

Low-Fire, Mid-Fire, and High-Fire Glazes Compared

Use the table below to match your kiln type, clay body, and desired outcome to the correct glaze temperature category before buying or mixing materials.

For most home studio potters, commercial cone 6 glazes on a vitrified stoneware body give the best combination of food safety, color range, and firing reliability without requiring chemistry knowledge.

What Are the Main Types of Ceramic Glazes by Surface Finish?

Ceramic glazes divide into three primary surface finish types: gloss glazes (reflective, smooth, easy to clean), matte glazes (non-reflective, velvety, light-scattering), and satin glazes (semi-matte, between gloss and matte). The finish type is not cosmetic: it determines food safety, cleanability, and chemical durability.

According to Robin Hopper in The Ceramic Spectrum (1984, revised 2008), surface finish is controlled by the silica-to-alumina ratio in the glaze recipe and the cooling rate after firing. High silica and fast cooling produce gloss. High alumina and slow cooling produce matte surfaces through micro-crystal formation.

Gloss Glazes

Gloss glazes produce a reflective, glassy surface with minimal light scattering. The silica-to-alumina ratio in gloss glazes typically runs 7:1 to 10:1, creating a smooth glass melt with few crystalline interruptions to the surface.

This happens because the high silica content forms a continuous glass network at firing temperature. The alumina content is kept low enough to prevent crystal nucleation while still stabilizing the melt. When cooled normally (kiln shut off and allowed to cool naturally over 8 to 12 hours), the glass remains amorphous and reflective.

If the silica content drops too low (below 5:1 ratio), the surface becomes satin or matte. If the cooling rate is slowed to 24 hours or more, crystals may still form even in high-silica formulas, dulling the gloss.

Amaco Potters Choice gloss glazes are the most popular cone 6 commercial gloss line for studio potters. Gloss glazes are the easiest surface to clean and the most food-safe finish for functional dinnerware.

Matte Glazes

Matte glazes produce a non-reflective, velvety surface. The matte effect comes from two possible mechanisms: high alumina content (chemical mattes) or controlled slow cooling (crystalline mattes).

Calcium mattes use a high CaO ratio. During cooling, the calcium forms anorthite micro-crystals. These crystals scatter light instead of reflecting it, creating the signature velvety surface at the cost of slightly reduced chemical durability compared to gloss surfaces.

This crystal formation only occurs when the cooling rate drops below 150°F per hour between cone 6 and cone 4 (approximately 2,232°F to 2,167°F). If the kiln cools too fast, crystals do not form and the surface comes out glossy despite the high-alumina formulation.

If the cooling is too slow (below 50°F per hour), the crystals grow too large and the surface becomes rough rather than velvety, feeling like fine sandpaper instead of smooth matte. Coyote matte glazes are formulated for reliable matte surfaces at standard electric kiln cooling rates.

Satin Glazes

Satin glazes occupy the middle ground between gloss and matte, with a soft sheen that reflects some light but does not produce a mirror finish. Satin surfaces are created by partially interrupting the glass surface with controlled alumina levels (intermediate silica-to-alumina ratios of 5:1 to 7:1).

Satin glazes combine the cleanability advantages of gloss with the tactile appeal of matte. For functional ware that will be handled frequently (mugs, teapot handles, bowl exteriors), satin surfaces offer the best user experience without sacrificing food safety or chemical durability.

Satin glazes are the most forgiving surface finish for beginners. They hide minor application inconsistencies better than gloss and do not require the precise cooling control of mattes.

For functional dinnerware that will see daily use and dishwasher cycles, gloss glazes on the interior contact surface with satin or matte exteriors give the best combination of cleanability and tactile quality.

Specialty and Atmospheric Glaze Types

Specialty glazes require specific kiln atmospheres, unusual cooling cycles, or specialized application techniques to achieve their signature surfaces. These glazes produce the most sought-after ceramic aesthetics but demand more technical knowledge and equipment than standard oxidation glazes.

Crystalline Glazes

Crystalline glazes produce visible zinc silicate crystal formations that grow within the glass matrix during a precisely controlled cooling cycle. The crystals appear as starburst or snowflake patterns against a colored background, making each piece completely unique.

This happens because zinc oxide levels above 20% in the glaze recipe create a supersaturated solution in the molten glass. During a multi-stage cooling cycle (soaking at 1,850°F / 1,010°C for 3 to 5 hours), zinc atoms bond with silica to form willemite crystals (Zn2SiO4) that grow outward from nucleation points on the clay body surface.

The crystal growth only occurs if the cooling cycle includes stable temperature holds within the crystal formation window (1,900°F to 1,750°F / 1,038°C to 954°C). If the kiln cools without holds through this range, no crystals form and the surface emerges as a standard transparent or translucent zinc glaze with no visible crystal structure.

If the hold temperature drops below 1,750°F, crystal growth stops but the glaze has not yet solidified: the result is a surface with tiny, underdeveloped crystal specks rather than full starburst patterns. Diane Creber’s Crystalline Glazes is the definitive reference on crystal chemistry and firing schedules.

Ash Glazes

Ash glazes use wood ash (or synthetic ash recipes) as the primary flux source, producing surfaces with distinctive running effects, rivulets, and warm olive-to-amber color palettes. Wood ash from different tree species (oak, pine, apple, rice straw) produces unique color responses due to varying calcium, potassium, and trace element content.

The mechanism is the high potassium and calcium oxide content in wood ash (typically 15 to 30% CaO, 5 to 15% K2O). These oxides act as powerful fluxes at cone 10 (2,381°F / 1,305°C) while the silica from the ash (30 to 50%) forms the glass network. Trace iron, manganese, and phosphorus create the characteristic olive, amber, and brown color variations.

Ash glazes only mature at cone 9 to 10 in reduction or wood-fired atmospheres. At cone 6 in oxidation, ash glazes remain dry and un-melted because potassium and calcium fluxes from raw ash activate at higher temperatures than the equivalent refined chemical fluxes used in mid-fire glazes.

Phil Rogers’ Ash Glazes (2003) documents ash glaze chemistry across multiple wood species and firing conditions, with specific oxide analyses for each ash type.

Shino Glazes

Shino glazes are traditional Japanese glazes producing surfaces from pearly white to bright orange, often with carbon-trapping effects that create dark grey markings within the glaze layer. Modern American shinos have evolved significantly from their Momoyama-period Japanese origins.

The mechanism for carbon trapping in shino glazes is specific and sensitive. Shino recipes use high feldspar content (typically 70 to 80% nepheline syenite or soda feldspar) with low clay content (10 to 15% kaolin). During early reduction (cone 012 to cone 08, 1,600°F to 1,750°F / 871°C to 954°C), the porous, soda-rich glaze surface absorbs carbon from the kiln atmosphere before the glaze seals over at higher temperatures.

Carbon trapping only works in gas or wood kilns with early, heavy reduction starting no later than cone 012. Electric kilns in oxidation produce flat white or pale orange shinos with no carbon marking, because there is no free carbon in the kiln atmosphere to trap.

If reduction starts too late (above cone 08), the glaze surface has already begun to seal. Carbon cannot penetrate and the surface fires to plain white with no trapped carbon markings. Standard cone 10 shino glaze recipes from Malcolm Davis and Virginia Wirt are the most widely used formulations in American studio pottery.

Celadon Glazes

Celadon glazes produce translucent blue-green to jade-green surfaces on porcelain and stoneware bodies. True celadon requires reduction firing to convert iron from its ferric (Fe2O3, brown) to ferrous (FeO, blue-green) state. The iron content is typically low: 0.5 to 2% iron oxide by weight in the glaze recipe.

In reduction, iron oxide (Fe2O3) loses an oxygen atom to become ferrous oxide (FeO). FeO functions as an active flux rather than a refractory colorant, lowering the glaze melt temperature and scattering light at a wavelength the eye reads as blue-green.

This shift from Fe2O3 to FeO only occurs in a gas or wood kiln with a carbon-rich atmosphere between cone 012 and cone 8. Electric kilns firing in full oxidation cannot replicate it regardless of glaze chemistry: the iron remains as Fe2O3 and produces yellow-amber to brown surfaces.

If reduction is introduced too late (above cone 6), the glaze surface has already begun to seal, trapping insufficient FeO. The result is a yellow-amber surface indistinguishable from oxidation firing. Traditional celadon glaze recipes use small amounts of iron oxide (1 to 2%) with high feldspar and silica content in a cone 9 to 10 reduction firing.

Tenmoku and Iron Saturated Glazes

Tenmoku glazes produce deep brown to near-black surfaces with iron crystal effects including oil-spot, hare’s fur, and tea dust patterns. These glazes use high iron oxide content: 6 to 12% by weight, far above the 0.5 to 2% used in celadons.

The mechanism is iron oxide supersaturation. At cone 9 to 10 (above 2,300°F / 1,260°C), the glaze dissolves iron oxide up to its saturation limit. During cooling, excess iron precipitates out as crystalline hematite (Fe2O3) on the surface in patterns determined by cooling rate, glaze viscosity, and kiln atmosphere.

Oil-spot patterns form when rapid cooling creates many small nucleation sites. Hare’s fur patterns form with slower cooling and more fluid glazes. Tea dust patterns require specific iron-to-magnesium ratios and extremely slow cooling cycles.

These patterns only develop in reduction firing at cone 9 to 10. In oxidation or at cone 6, the iron remains fully dissolved in the glass matrix and the surface appears as flat, featureless brown or black with no crystalline surface activity. Tenmoku and iron saturate cone 10 glazes represent some of the most technically demanding surfaces in studio ceramics.

Raku Glazes

Raku glazes are low-fire glazes designed for the raku firing process, where pots are removed from the kiln at peak temperature (1,800°F to 1,900°F / 982°C to 1,038°C) and placed into combustible materials for post-firing reduction. This process creates metallic lusters, crackle patterns, and smoke-darkened unglazed clay surfaces.

The mechanism is thermal shock and post-firing chemistry. When the red-hot pot hits the combustible material (newspaper, sawdust, leaves), the glaze surface is still soft enough to absorb carbon while cooling rapidly enough to crackle. The carbon penetrates the crackle lines and unglazed clay, turning them black while the glaze surface develops metallic copper and silver effects.

Raku glazes only work in the specific raku firing process with immediate post-firing reduction. They will not produce raku effects in a standard electric kiln firing with normal cooling, because the post-firing reduction step is what creates the signature surfaces.

If a raku-glazed pot is fired in a standard kiln and cooled normally, the surface emerges as a simple low-fire glaze with none of the metallic or crackle effects. Raku glazed ware is never food-safe due to the crackle pattern creating bacterial traps and the metallic surfaces potentially leaching copper and other metals. Raku glaze kits from Mayco and Amaco are the standard starting point for raku firing.

Salt and Soda Glazes

Salt and soda firing are atmospheric glazing processes where sodium vapor introduced into the kiln at peak temperature reacts with silica in the clay body to form a sodium silicate glaze directly on the pot surface without applying glaze beforehand. No glaze brushing or dipping is required: the glaze forms from vapor.

The mechanism is a gas-solid reaction. At cone 9 to 10 (above 2,300°F / 1,260°C), salt (NaCl) introduced into the kiln decomposes into sodium and chlorine gas. Sodium vapor bonds with silica and alumina in the exposed clay body surface, forming sodium aluminosilicate glass (the glaze). Soda firing uses soda ash (Na2CO3) or baking soda (NaHCO3) instead of salt, avoiding toxic chlorine gas production.

This reaction only occurs at cone 9 to 10 in a dedicated salt or soda kiln with a fuel-burning atmosphere. Electric kilns cannot be used because the sodium vapor permanently damages electric elements and thermocouples beyond repair.

If sodium introduction is too early (below cone 8), the clay body surface has not reached sufficient temperature to react and the sodium deposits as a dry white powder rather than a glass. If too late (after the kiln has peaked), the glaze does not build sufficient thickness for even coverage. The kiln itself becomes glazed over multiple firings, requiring periodic rebuilds. Salt and soda ware is food-safe when fired to full maturity on vitrified clay bodies.

Luster and Overglaze Enamels

Luster glazes and overglaze enamels are applied to already-fired glazed surfaces and fired a third time at extremely low temperatures (cone 018 to 015, 1,300°F to 1,450°F / 704°C to 788°C). They produce metallic gold, platinum, mother-of-pearl, and bright decorative effects that cannot survive higher firing temperatures.

The mechanism is a thin film deposition rather than a glass melt. Luster solutions contain metallic compounds dissolved in organic solvents. During the low-temperature third firing, the organic vehicle burns off and a micron-thin layer of actual gold, platinum, or bismuth oxide deposits onto the glaze surface and bonds through a combination of mechanical adhesion and weak chemical bonding.

This ultra-thin metal film is fragile. Luster surfaces are not dishwasher-safe and wear off with repeated use and abrasion. Luster-decorated ware is not food-safe on contact surfaces and should be used only on decorative ware or the exterior non-contact surfaces of functional items. Duncan and Mayco luster overglazes are the standard commercial products.

Specialty glazes reward technical knowledge with surfaces that cannot be achieved any other way. For potters who want surfaces beyond what commercial brush-on glazes can deliver, atmospheric and specialty techniques open an entirely different creative vocabulary.

How to Choose the Right Glaze Type for Your Work

The glaze type you choose must match three things: your kiln’s maximum temperature capability, your clay body’s firing range, and your functional requirements (food safety, durability, aesthetic goals). Getting any one of these wrong guarantees kiln failure.

Start with your kiln. An electric kiln rated to cone 6 cannot fire cone 10 reduction glazes. A gas kiln can fire any temperature range but may be overkill for low-fire work. The kiln is the non-negotiable constraint that eliminates temperature categories immediately.

Then match to your clay body. A cone 6 stoneware clay with under 1% absorption needs cone 5 to 6 glazes. Using cone 06 low-fire glaze on stoneware creates a glaze that melts while the clay remains porous: the glaze seals the surface but the body absorbs water through any pinhole or unglazed foot ring.

Using cone 10 glaze on a cone 6 clay body is worse. The glaze never melts while the clay over-fires, bloats, and potentially collapses in the kiln. The 400°F (222°C) temperature gap between cone 6 and cone 10 is absolute: cone 6 clay is not formulated to survive cone 10 without deformation.

The firing temperature locks every other decision. Get that wrong and nothing else matters. Choose a glaze rated for your kiln’s cone range first, then match the clay body, and only then consider color and finish. Understanding glaze application and compatibility testing is essential before committing to a large batch of any glaze type.

Common Mistakes When Choosing Ceramic Glaze Types

Most glaze failures happen before a brush ever touches bisqueware. The mistakes are in the selection stage: choosing glazes incompatible with your kiln, clay body, or functional requirements.

Mistake 1: Matching Glaze Cone to Kiln Capability Without Checking Clay Body

A cone 6 glaze on a cone 6 stoneware body works. A cone 6 glaze on a cone 04 earthenware body is a disaster: the clay over-fires and bloats or melts while the glaze matures correctly. Always verify that your clay body and glaze share the same firing range.

The Orton Foundation documents that a clay body’s published cone range represents the full vitrification window. Firing outside that window: even one cone hotter or cooler: risks bloating, warping, or incomplete vitrification.

Mistake 2: Assuming All Glazes Are Food-Safe Once Fired

Not all fired glazes are food-safe. Glazes containing barium carbonate, lithium carbonate above 2%, or high levels of copper can leach into acidic food even after correct firing. Raku glazes are never food-safe due to crackle patterns and metallic surface chemistry.

Per ASTM C738 testing standards, ceramic glazes intended for food contact must not release more than 0.5 mg/L of lead or 0.25 mg/L of cadmium when tested with 4% acetic acid at room temperature for 24 hours. Always verify food safety certifications on commercial glazes or have custom glazes laboratory tested before selling functional ware.

Mistake 3: Choosing Glaze Type Without Understanding Kiln Atmosphere Requirements

Reduction glazes (celadon, shino, copper red, temmoku) cannot achieve their signature surfaces in an electric kiln. The carbon-rich atmosphere required for the Fe2O3 to FeO conversion simply does not exist in oxidation firing.

If you only have access to an electric kiln, you are limited to oxidation glaze types: gloss, matte, satin, and commercial adaptations labeled as “celadon-look” or “shino-look” which approximate reduction surfaces through different chemistry but are not true reduction glazes.

Mistake 4: Applying Glaze Too Thick or Too Thin for the Glaze Type

Gloss glazes at 2mm thickness produce a clean, even surface. The same 2mm of a highly fluid crystalline or ash glaze can run completely off the pot and fuse it to the kiln shelf. Matte glazes applied too thin (under 1mm) fire to a patchy, semi-gloss surface that reveals the clay body through thin spots.

Push a pin tool through wet glaze to the clay surface to check thickness. Each glaze type has an optimal application range listed on the manufacturer’s technical data sheet or in published recipes.

Mistake 5: Skipping Test Tiles Before Committing to Production Work

Every glaze type behaves differently on different clay bodies, at different thicknesses, and in different kiln positions. A crystalline glaze that produces spectacular crystals on a test tile placed in the kiln’s hot zone may produce zero crystals on the same clay body placed in a cooler zone.

Test every glaze on your specific clay body, at your intended application thickness, in your specific kiln, before glazing production work. A single test tile costs $2 in materials and one firing cycle. Re-glazing or discarding 50 failed mugs costs hundreds of dollars and weeks of studio time. Matching glaze to the right clay body choice is the foundation of successful glaze results.

Every mistake on this list is avoidable with a systematic approach to glaze selection. Start with your kiln, verify your clay body, test before committing, and never assume a glaze is food-safe just because it is sold as a ceramic glaze.

Frequently Asked Questions About Ceramic Glaze Types

What is the difference between brushing glaze and dipping glaze?

Quick Answer: Brushing glazes contain gum additives that allow them to flow from a brush without dripping excessively. Dipping glazes have a thinner consistency with specific gravity of 1.45 to 1.50 and no added gums. Brushing glazes cost more per ounce. Dipping glazes are more economical for production work.

Brushing glazes are formulated with CMC gum or Veegum T to create a gel-like consistency that suspends glaze particles and brush-applies smoothly in 2 to 3 coats. Dipping glazes use water-thin consistency for fast, even coverage by immersion.

You can convert a dipping glaze to brushing by adding 0.5 to 1% CMC gum solution. You cannot convert brushing glaze to dipping by thinning with water: the gum additives prevent the glaze from reaching proper dipping thickness. Buy the format that matches your application method.

Can I use cone 10 glaze in a cone 6 kiln?

Quick Answer: No. Cone 10 glazes fired to cone 6 produce a dry, chalky, un-melted surface because the feldspar-based flux system requires temperatures above 2,300°F (1,260°C) to decompose and form glass. The 400°F (222°C) temperature gap is absolute and irreversible.

The feldspar minerals in cone 10 glazes (Custer feldspar, G-200, nepheline syenite in high percentages) do not begin to melt until approximately cone 8 (2,280°F / 1,249°C). Below this temperature, they remain as inert mineral particles suspended in a matrix of other glaze ingredients that may partially sinter but never form true glass.

The result of under-firing cone 10 glaze is a surface that looks and feels like fine sandpaper bonded to the pot. It is neither visually appealing nor functional. Never attempt to fire above your kiln’s rated maximum cone to compensate: element and brick damage is immediate and expensive.

Why did my matte glaze come out glossy?

Quick Answer: Your kiln cooled too fast. Matte glazes require slow cooling (below 150°F per hour) between the peak temperature and approximately cone 4 (2,167°F / 1,186°C) for micro-crystals to form. If the kiln cools naturally without a controlled slow-cool program, the crystals do not nucleate and the surface stays glossy.

The cooling rate through the crystal formation window (cone 6 to cone 4, approximately 2,232°F to 2,167°F / 1,222°C to 1,186°C) is the primary control for matte surfaces. Fast cooling (over 250°F per hour) freezes the glass before crystals can grow.

To fix this, program a controlled cool segment in your kiln controller: hold at 1,900°F (1,038°C) for 30 minutes, then cool at 125°F per hour to 1,500°F (816°C) before letting the kiln cool naturally. This gives matte crystals time to form without over-growing. Verify results with witness cones at multiple shelf levels.

Are commercial brush-on glazes safe for food contact?

Quick Answer: Most major brand cone 6 brush-on glazes (Amaco Potters Choice, Coyote, Mayco Stoneware) are AP certified and food-safe when properly applied and fired to full maturity on vitrified clay. Always verify the specific glaze label states “food-safe” or “dinnerware safe.”

The ACMI AP (Approved Product) certification verifies that the glaze contains no materials in sufficient quantities to be toxic or harmful even if ingested. However, certification only applies when the glaze is fired exactly per manufacturer instructions: correct clay body, correct cone, correct application thickness.

Even food-safe glazes can become unsafe if under-fired, applied over non-vitrified clay, or layered with non-food-safe glazes. Always fire food-contact ware with a witness cone pack to verify the kiln reached the correct heat work. The cone tells you the truth regardless of what the digital controller display shows.

Why does my glaze crawl away from the clay surface during firing?

Quick Answer: Glaze crawling occurs when the liquid glaze does not properly wet the bisqueware surface due to dust, oils from skin contact, overly dense bisque (fired too high), or glaze applied too thickly. The glaze pulls back into islands, exposing bare clay.

The mechanism is a surface tension problem. Any contaminant on the bisque surface (dust, finger oils, wax residue, kiln wash overspray) prevents the water in the wet glaze from penetrating the porous bisque. As the water drives off during early heating, the glaze layer shrinks and pulls away from the contaminated spots.

To prevent crawling, wipe all bisqueware with a damp sponge 24 hours before glazing to remove dust. Handle bisque only by the foot ring after cleaning. Do not bisque fire above cone 04: over-fired bisque is too dense for proper glaze adhesion. Keep glaze application thickness under 2mm for most formulations.

Can I mix different commercial glaze brands on the same pot?

Quick Answer: Yes, with caution and testing. Layering different brands of the same firing range (all cone 6) can produce beautiful effects, but always test on a tile first. Mixing brands can cause unexpected crawling, pinholes, or delayed crazing due to CTE mismatches between different manufacturer formulas.

Each glaze formulator uses different flux systems, specific gravities, and thermal expansion coefficients. When two glazes with different CTEs are layered, the tension between the layers can create delayed crazing or shivering weeks or months after firing. This is especially dangerous for functional dinnerware.

Test any brand combination on a test tile with a kiln-washed shelf underneath in case of unexpected running. Check the test tile for crazing with ink or a magnifying glass, then re-check after thermal shock testing (boiling water to ice water cycle) before committing to production work.

What type of glaze is best for beginners?

Quick Answer: Commercial cone 6 brush-on gloss glazes on cone 6 stoneware clay are the most forgiving and reliable choice for beginners. They produce food-safe, dishwasher-safe surfaces at temperatures achievable in any electric kiln without requiring glaze chemistry knowledge or gas kiln operation skills.

Gloss glazes are more forgiving of minor application errors than mattes and do not require controlled cooling cycles. Commercial formulations eliminate the variable of raw material measurement and mixing errors that plague beginner-mixed glazes from recipes.

Start with 3 to 5 basic colors from one brand line (Amaco Potters Choice or Mayco Stoneware are the most widely available). Master consistent application thickness with a glaze hydrometer reading 1.45 to 1.50 specific gravity. Learn to fire your specific kiln to a true cone 6 verified by witness cones. These three skills: consistent application, correct specific gravity, and verified heat work: are the foundation that all advanced glaze work builds upon.

Ready-to-use beginner glazes to start your pottery journey offer the simplest entry point for new potters who want reliable results without chemistry complexity.

Is raku pottery food-safe?

Quick Answer: No. Raku-fired pottery is never food-safe. The crackle glaze pattern creates bacterial traps. Metallic luster surfaces can leach copper and other metals into food. The low-fire clay body remains porous and absorbs liquids through any unglazed surface. Raku ware is for decorative use only.

The raku process creates glaze surfaces that are intentionally cracked and crazed for aesthetic effect. These cracks extend through the glaze layer to the porous clay body underneath, creating pathways for liquids and bacteria. No amount of sealing or surface treatment can make a crackle-glazed raku pot food-safe.

Additionally, raku metallic lusters achieve their effects through copper oxide, cobalt, and other metal compounds that are not chemically bound in a durable glass matrix. Acidic foods and hot liquids accelerate leaching. Display raku pottery as art. Never use it for food or drink.

How do I know if my glaze fired to the correct cone?

Quick Answer: Place Orton witness cones (a cone 5, cone 6, and cone 7 set) on every kiln shelf level during every glaze firing. The cone 5 should be fully bent. The cone 6 should be bent to a 90-degree tip touching the shelf. The cone 7 should be untouched or barely starting. Only the cone 6 tells you the truth about actual heat work.

Electronic kiln controllers display temperature from a thermocouple, not heat work. Thermocouples drift over time, reading 10°F to 30°F (5°C to 15°C) off calibration annually. Pyrometric cones measure the combined effect of temperature and time, which is what actually matures your glaze.

A kiln can display 2,232°F (1,222°C) on the controller while the witness cone 6 on the bottom shelf shows under-fired by half a cone due to temperature variation within the kiln. The cones never lie. Trust them over the controller reading every time and adjust your firing schedule accordingly.

What causes pinholes in my glaze surface?

Quick Answer: Pinholes form when gases escaping from the clay body during glaze firing cannot pass through the glaze layer before the glaze surface seals over. The trapped gas creates a bubble that pops and leaves a pinhole. The most common causes are insufficient bisque firing, rapid glaze firing, or clay bodies with high organic content.

The mechanism is a timing problem during the glaze firing. Between 1,600°F and 1,900°F (871°C and 1,038°C), the clay body releases chemically bound water, sulfur compounds, and residual carbon from organic burnout. If the glaze surface seals before these gases fully escape, bubbles form and pop.

To fix pinholes: bisque fire higher (cone 04 instead of cone 06) to drive off more volatiles. Slow the glaze firing rate between 1,600°F and 1,900°F to give gases more time to escape before the glaze seals. Add a 15-minute hold at 1,850°F (1,010°C) to allow surface bubbles to heal before the kiln peaks and cools.

Do I need a different glaze for porcelain vs stoneware?

Quick Answer: Yes, often. Porcelain has a lower thermal expansion coefficient (CTE) than most stoneware bodies. Glazes formulated for stoneware may craze on porcelain due to CTE mismatch. Many commercial glaze lines specify whether they are formulated for stoneware, porcelain, or both.

Stoneware typically has a CTE of 6.0 to 7.5 x 10⁻⁶/°C. Porcelain runs lower at 5.0 to 6.5 x 10⁻⁶/°C. A glaze that fits stoneware perfectly (slightly lower CTE than the body, putting the glaze in compression) may have a CTE too high for porcelain, putting the glaze in tension and causing crazing.

Always test commercial glazes on your specific porcelain body with a crazing test: apply the glaze to a test tile, fire to mature cone, and check for cracks with ink or under magnification. If crazing appears immediately or after thermal shock testing, the CTE mismatch is unacceptable for functional ware. Switch to a porcelain-formulated glaze or adjust your stoneware glaze with additional silica to lower its CTE.

How many coats of brush-on glaze should I apply?

Quick Answer: Most commercial brush-on glazes require 3 even coats, applied in alternating directions, totaling approximately 2mm wet thickness. Always follow the specific manufacturer’s instructions on the bottle label. Too few coats produce thin, patchy color. Too many coats cause running, crawling, or blistering.

Three thin coats produce a more even surface than one or two thick coats because each coat can dry completely between applications, preventing the surface tension problems that cause crawling. Apply with a soft fan brush for the smoothest finish.

For dipping glazes, a 3-second immersion typically deposits the correct thickness when specific gravity is maintained at 1.45 to 1.50. Measure with a pin tool through the wet glaze to verify 2mm thickness on your first few pieces until you develop a calibrated eye for proper application thickness.

Can I use low-fire glaze on stoneware?

Quick Answer: You can apply cone 06 to 04 low-fire glaze to stoneware, but the results are problematic. The glaze will melt and seal the surface while the stoneware clay body remains under-fired and porous (absorption above 3%). Any pinhole or unglazed area allows water absorption into the clay, causing eventual cracking, mold growth, or freeze-thaw failure.

The glaze-to-body fit is chemically wrong. Low-fire glazes are formulated for the high CTE of earthenware clay bodies (7.0 to 9.0 x 10⁻⁶/°C). Stoneware CTE is lower (6.0 to 7.5 x 10⁻⁶/°C). This mismatch causes the glaze to craze heavily or, in severe cases, shiver off the pot completely.

If you want the look of low-fire glaze colors on a durable body, use mid-fire stoneware with commercial cone 6 glazes that replicate low-fire color palettes. Understanding the differences between ceramic types helps you choose materials that work together rather than fighting each other in the kiln.

What is the difference between underglaze and glaze?

Quick Answer: Underglaze is a colored decoration applied to greenware or bisqueware that does not form a glass surface on its own. It requires a clear glaze over the top to seal and protect the color. Glaze is the glass coating that seals the clay and creates the final durable surface. Underglaze provides the decoration. Glaze provides the glass.

Underglazes are essentially colored slips or engobes formulated to mature at a wide range of temperatures without fluxing into a glass. Amaco Velvet underglazes are the industry standard for brush-applied underglaze decoration. They fire true to color under clear glaze at any temperature from cone 06 to cone 10.

Underglaze alone fires to a matte, chalky surface that is not food-safe and stains easily. The clear glaze overglaze layer provides the glass seal, chemical durability, and food safety. Underglaze plus clear glaze is the most versatile decoration method in ceramics because the color does not move or blur during firing the way many colored glazes do.

Conclusion

Choosing the right type of ceramic glaze is not about preference or aesthetics: it is about matching chemistry to kiln capability, clay body vitrification, and food safety standards. The firing temperature locks every other decision, and getting it wrong means wasted materials, ruined kiln shelves, and pottery that fails in daily use.

Start with a quality cone 6 stoneware clay, match it with food-safe commercial cone 6 glazes, and verify every firing with witness cones. Master one glaze type thoroughly before exploring specialty and atmospheric techniques. Begin with reliable ready-made glazes to get started and build your glaze knowledge from a foundation of consistent, successful results.

Test every new glaze on your clay body, in your kiln, with your application method. A single test tile saves you from kiln disasters that cost hundreds of dollars and weeks of studio time. Glaze knowledge accumulates one firing at a time.

Davivy 16'' X 13.5'' Oval Vessel Sink with Pop Up Drain,Bathroom Sinks Above Counter,White Ceramic Vessel Sink,Bathroom Vessel Sinks,Counter top Sink,Oval Sink Bowls for Bathroom

SHACO Wall Mounted Bathroom Sink with Towel Rack, 21" X 12" Modern Wall Mount Sink, Commercial Small Bathrooms Wall Hung Sinks, White Rectangular One Hole Porcelain Ceramic Sinks

Scarabeo 8031/R-100B-Two Hole Teorema Rectangular Ceramic Wall Mounted/Vessel Sink, White