Raw Materials

Most of us buy commercial glazes at some point—ready-made buckets that we can dip or brush onto pots. But look at any manufacturer’s label: the ingredients ultimately trace back to the same types of minerals, clays, and oxides that exist in nature. When you decide to mix your own glazes, you’ll be using these raw materials directly—scooping powders like kaolin, feldspar, or silica from your own bins, measuring and blending to create infinite variations.

Learning to work with raw materials has some big advantages:

• Cost and Control: Bulk minerals are often more economical, especially if you go through a lot of glaze. Plus, you can fine-tune recipes for specific surfaces or colors.
• Creative Freedom: Want to push a glaze toward a softer matte finish or a richer blue? A small tweak in your feldspar or clay content can make a noticeable difference.
• Deeper Understanding: When you know what each material contributes (flux, stabilizer, glass-former, colorant), troubleshooting becomes easier.

It’s a bit like learning to cook- not only do you save money from eating less at restaurants, but you gain valuable new understanding and appreciation for the art and science of cooking.

Where Do Materials Come From?

In essence, raw ceramic materials are Earth ground into powder. Large quarries or open pits yield the clays and minerals we know as feldspar, silica, kaolin, and more. These raw deposits may be relatively pure—or require washing and refining to remove impurities. Finally, they’re dried, milled, and bagged, making their way from the mine to your studio shelf.

• Clays (Kaolin, Ball Clay): Form when feldspar-rich rocks decompose over millions of years. Some clays remain white and iron-free (kaolin); others accumulate more organic material and iron (ball clay).
• Feldspar: Crystallizes from cooling magma in granite. Different ratios of sodium, potassium, and calcium yield the variations we use in glazes.
• Silica (Quartz, Flint): Earth’s most abundant mineral, mined from quartz veins, sandstone, or flint deposits.
• Limestone & Dolomite: Derived from ancient marine fossils (shells, coral) that formed thick layers of calcium- or magnesium-rich rock.
• Borates & Frits: Some borate minerals come from evaporated lakebeds; frits are man-made blends of common minerals, melted and ground into a consistent powder.
• Colorants (Cobalt, Iron, etc.): Cobalt is often found in specific ore bodies—sometimes as a by-product of copper or nickel mining—while iron is abundant in many rock and clay deposits, giving materials a characteristic red or brown hue.

Whether they begin as a mountain of granite, a marine limestone bed, or a seam of pure white clay, all of these raw materials connect your glazes and clay bodies to a deep geological story. By the time you measure them into a recipe, they’re standardized powders in a bag. But behind each one is a unique journey from Earth’s crust to your studio.

Theoretical vs. Real Materials

In Oxides in Glazes, we described glazes in terms of oxides—SiO₂ (silica), Al₂O₃ (alumina), various fluxes (Na₂O, K₂O, CaO, MgO, B₂O₃), and so on. But in the studio, you won’t have jars labeled “Alumina” or “Silica” in pure form. You won’t even have “Potash Feldspar” or “Kaolin”!

The actual materials we use in the studio come from various natural sources and contain impurities and inconsistencies. So, instead of the theoretical material “Potash Feldspar” with the pure chemical formula K₂O·Al₂O₃·6SiO₂, our studio will be stocked with real-world materials like Custer Feldspar or Mahavir, and each of these will have a slightly different analysis and contain other oxides like sodium, iron, calcium, etc.

Even for a specific type of material like Custer Feldspar there may be different analyses for different batches of the material at different times. A feldspar deposit might gradually shift from high potash content to higher silica. Same brand name, slightly different results in the kiln.

A sample of analyses for Custer Feldspar, a type of Potash Feldspar:

Essential Materials for Glaze Mixing

If you’re new to making your own glazes, you do not need every possible mineral. A core set of raw materials will get you quite far. The most important thing to focus on is the oxides that each material sources. For example, if you don’t have any materials that contain boron, you won’t be able to make most mid-fire glazes. (See Oxides in Glazes for the most important oxides.)

Common Base Ingredients for All Temperatures

These appear in nearly every glaze recipe, from earthenware to high-fire:

1. Silica

   • Oxide: SiO₂
   • Role: Main glass-former. Without silica, you simply wouldn’t get a proper glassy surface.
   • Theoretical Material: Silica (Flint, Quartz)
   • Notes: Sold in various mesh sizes, 200–325 are common. In glazes, the finer 325-mesh silica is preferred, while for clay bodies 200-mesh silica is often used. Often sold as generic “silica”, actual products like SIL-CO-SIL  are high-purity (>99.5% SiO₂), so most recipes just use the generic silica . On its own, it melts at very high temperatures, so you’ll need fluxes to lower its melting point.

2. Kaolin

   • Oxides: Al₂O₃ + SiO₂
   • Role: Provides alumina (for stability in the melt) and clay content for suspension in the bucket.
   • Theoretical Materials: Kaolin , Calcined Kaolin 
   • Common Commercial Materials: Edgar Plastic Kaolin (EPK) , Grolleg Kaolin , Tile #6 Kaolin 
   • Notes: Kaolins are relatively pure and fire white; ball clays are similar but contain more iron or organics. Many older recipes use the theoretical material for which you can usually just swap out for your particular commercial kaolin. For exact subsitutions you can use Glazy Target & Solve to swap one commercial kaolin for another, but 1-1 substitutions often work just fine, especially when amounts are <10%.

3. Feldspar
   • Oxides: K₂O/Na₂O (flux), Al₂O₃, SiO₂
   • Role: Core flux at mid/high-fire; partial flux at low-fire.
   • Theoretical Materials: Potash Feldspar , Soda Feldspar , Nepheline Syenite 
   • Common Commercial Materials: Potash Feldspars: Custer Feldspar , Mahavir Feldspar ; Vardhman Potash  Soda Feldspars: Minspar 200 , Nepheline Syenite: Nepheline Syenite A270 
   • Notes: The ratio of sodium to potassium influences melting behavior, glaze texture, and color response. For low & mid-fire, Nepheline Syenite and Soda Feldspar are often used due to their stronger fluxing power. For high-fire, Potash Feldspar is commonly-used.

4. Whiting

• Oxides: CaO (releasing CO₂ during firing)
• Role: Calcium flux for durable, sometimes glossy surfaces at high temperatures.
• Theoretical Materials: Whiting (Calcium Carbonate) 
• Common Commercial Materials: Whiting (Calcium Carbonate) . Wollastonite (Calcium Silicate)  is another source of CaO that also provides SiO₂.
• Notes: As with silica, whiting is often high-purity (>98% CaCO₃), so most recipes just specify the generic whiting .

5. Zinc Oxide

• Oxides: ZnO
• Role: Another high-fire flux that can affect surface texture and crystal formation.
• Notes: Common in special-effect glazes at high temperatures.

6. Dolomite or Talc

• Oxides: MgO + CaO (dolomite); MgO (talc)
• Role: Magnesium can yield silky matte surfaces and reduce crazing by lowering thermal expansion.
• Theoretical Materials: Talc , Dolomite 
• Notes: Small chemistry shifts in dolomite vs. talc can change the look and feel of the fired glaze.

Mid-Fire Essential Base Ingredients

• Boron Source

  • Oxides: B₂O₃ + additional fluxes (Na₂O, CaO, etc.)
  • Role: Boron is a powerful flux that lowers melting temperature—critical for cone 5–6 glazes.
  • Common Commercial Materials:
    • Frits: Ferro Frit 3134 , Ferro Frit 3124 , Ferro Frit 3195 , and others .
    • Gerstley Borate , Colemanite , Ulexite , Borax** 
  • Notes: Frits are consistent and less soluble than raw borates like Gerstley Borate.

Common Additive Ingredients (All Temperatures)

In addition to the base ingredients which make up the “body” of the glaze, various additives are often added to impart color, modify opacity, aid suspension, etc.:

• Opacifiers: Zircopax (zirconium silicate) sourcing ZrO₂ or Tin Oxide (SnO₂) for white or opaque glazes.
• Colorants: Iron, cobalt, copper, manganese, chrome, rutile—all usually used in small amounts (often <5%).
• Suspension Aids: Bentonite  or Veegum T  keep glazes from settling into a sludge at the bottom of your bucket.

How Much Material Should You Buy?

When first stocking your glaze lab, it’s wise to think about how quickly you’ll use each type of material. Some ingredients like silica and feldspar are used in almost every recipe, while others—like colorants—are only needed in small doses. Here’s a rough guide for starting out:

Bulk Materials (50 lb Bags)

For the most commonly-used materials, it’s usually more economical (often 20-30% cheaper) to buy full 50lbs bags since you’ll go through them steadily.

Materials to consider buying in bulk:

• Feldspar: For high-fire it’s common to use Potash, while for mid-fire you might choose Nepheline Syenite.
• Silica
• Kaolin
• Whiting
• Boron Frit: For mid-fire it may be worth it to invest in a 50-pound bag of commonly-used boron frit to save money in the long-run.

Medium Quantities (5–25 lb)

• Magnesium Sources like Dolomite & Talc
• Wollastonite, an additional calcium source.
• Zinc Oxide
• Opacifiers like Zircopax or if you make a lot of opaque white glazes.
• Ball Clay, an additional source of alumina.
• Red Iron Oxide is the most commonly used colorant and relatively inexpensive.

Small Quantities (1–2 lb or Less)

• Due to skyrocketing prices, you may want to keep lithium sources like Lithium Carbonate and Spodumene to a minimum.
• Also due to cost, Tin Oxide. In glazes that use tin as an opacifier, you may want to use Zircopax, instead.
• Colorants (Iron, Cobalt, Copper, Chrome, Manganese, etc.) Most colorants rarely exceed 5% in a glaze recipe, with many used below 1%. A pound of cobalt can last years unless you’re producing massive volumes of deep-blue glazes.
• Bentonite or Veegum T for suspension can also be bought in small amounts since only a few percent is added to most recipes.
• Various other additives like CMC Gum, Soda Ash, Epsom Salts, etc.

Practical Tips

1. Check Local Suppliers: Buying bags locally avoids high shipping costs. If you have to ship, it may be cheaper to purchase your “bulk materials” all at once.
2. Coordinate with Others: If you’re part of a studio or community, consider group buys to split big bags of feldspar or silica.
3. Watch Shelf Life: Most minerals are stable for years if kept dry; however, some raw borates or materials that absorb moisture can clump over time, so buy only what you can reasonably use in a year or two.
4. Space and Storage: 50 lb bags take up space. Make sure you have airtight containers or sturdy bins to keep powders from getting damp or spilling.

A little planning upfront will save you money (and storage headaches) while ensuring you have the right materials on hand whenever glaze inspiration strikes.

Stocking Your First Glaze Lab

When starting out with making your own glazes, it can be challenging to figure out how to stock your glaze lab. It can be discouraging to come across a beautiful glaze recipe only to find that you don’t have the materials to make it.

The shopping lists below were created by looking at Glazy’s “Most Commonly-Used Materials”. By stocking your lab with the most common materials, it’s more likely that you’ll be able to make most of the recipes you find on Glazy.

For the full data & charts see “Most Commonly-Used Materials”

Prices are from Laguna/Axner , but relative prices should be consistent amongst different suppliers.

Mid-Fire Base Ingredients Shopping List

Based on the most commonly-used base ingredients for mid-fire, here is an example shopping list for around $500.

Nepheline Syenite is used a lot and can be your primary source of alkaline fluxes, although it’s also good to have some Potash and Soda feldspar. Ferro Frit 3134 would be the primary source of boron, although the list adds other sources like Gerstley and frits for convenience. Lithium sources are extremely expensive these days, so you might want to skip them entirely. You can make Calcined Kaolin yourself by putting regular kaolin in your bisque kiln.

Mid-Fire Additives Shopping List

Below is a sample shopping list costing about $250. Multiple sources of iron are included because they’re fairly cheap, as well as two sources of cobalt (oxide & carbonate) because they are used so frequently, but you could always go with a single source and use material substitution. For silicon carbide you could go with a 300-600 mesh for lava glazes, 1000-1200 mesh for localized reduction glazes, or just leave it out if you’re not interested in those effects. I listed natural bone ash but you could go with the more expensive synthetic.

High-Fire Base Ingredients Shopping List

For high-fire our list of base ingredients is similar to mid-fire, except we don’t require an expensive source of boron, resulting in our sample shopping list being about $100 cheaper than for mid-fire.

High-Fire Additives Shopping List

Further Resources

• The Ceramic Materials Atlas 
• Major Oxides in Glazes – In-depth look at fluxes, glass-formers, stabilizers, and colorants.
• Chemical Analyses and Formulas in Ceramics – How to calculate oxide percentages, unity formulas, and expansions.
• Glazy Materials  – Community-curated analyses for many commercial raw materials.