Safety Guidelines for Making Your Own Ceramic Glazes

Mixing your own glazes involves handling fine powders, oxides, and potentially toxic metals. As a beginner, you can absolutely make glazes safely, provided you follow some straightforward guidelines.

Key Hazards When Making Glazes

While glaze mixing can be safe, there are some hazards to be aware of:

1. Dust Inhalation (Silica, Metal Oxides): The most pervasive risk in ceramics. Fine glaze powders can become airborne and lodge in your lungs, potentially leading to respiratory diseases like silicosis over long-term exposure.

2. Toxic Ingredients (Lead, Cadmium, etc.): Some raw glaze materials (especially older or specialty formulations) contain heavy metals that are harmful if ingested or inhaled.

3. Skin Contact & Irritation: Wet or dry glaze materials (especially soluble metallic salts) can irritate skin or cause allergic reactions with repeated exposure.

4. Kiln Fumes: Although primarily a firing issue, know that certain glaze materials (e.g., manganese, copper) can release potentially hazardous vapors at high temperatures.

Safe Studio Practices

1. Control Dust (Work Wet, Clean Wet)

• Wear a Proper Mask/Respirator: Use an NIOSH N95, P100 or higher respirator whenever measuring or mixing dry powders. Basic paper masks are ineffective for fine silica. Make sure your respirator is the right size for your face and fits properly, and store it in a clean, dry container like a ziplock bag when not in use. Note that facial hair can prevent proper respirator sealing. Replace filters according to manufacturer’s recommendations (typically every 3-6 months under normal use).
• Mix in a Ventilated Area: A fan or open windows reduce dust accumulation. If possible, mix in a spray booth or under local exhaust ventilation. Fans should direct air away from your breathing zone and toward filtration.
• Dampen Spills & Surfaces: Avoid sweeping or vacuuming raw glaze dust with ordinary equipment (it blows the dust back). Instead, wipe surfaces with a damp sponge or use a HEPA-filter vacuum.
• Keep a Clean Space: Dry glaze drips or spilled powder can be dangerous if crushed underfoot and kicked up as dust later. Cleaning up promptly with water prevents future inhalation.

2. Use Personal Protective Equipment (PPE)

• Gloves: Nitrile or latex gloves protect skin from irritating or toxic materials (cobalt, chrome, copper).
• Eye Protection: Glaze splashes or powder can irritate eyes, so wear safety glasses when you’re vigorously mixing or sieving.
• Apron/Studio Clothing: Designate clothes you don’t mind getting dirty. Launder them separately to avoid bringing dust into your home.

3. Handle Raw Materials Responsibly

• Label All Containers: Whether it’s a bag of kaolin or a jar of mixed glaze, clearly mark what’s inside and any hazards (e.g. “Barium-containing—Handle with Care”).
• Avoid Lead & Cadmium: These metals can make stunning colors but are extremely risky. Avoid lead- or cadmium-based glazes entirely if making functional ware. Cadmium-based encapsulated stains may be used if handled and disposed of properly.
• Read Safety Data Sheets (SDS): Suppliers provide SDS docs that list toxicity and safe handling instructions. Keep them on hand for reference.
• No Eating or Drinking While Mixing or Glazing: A crumb in the wrong place can pick up toxic dust. Wash hands thoroughly before breaks or meals.

4. Mixing & Testing Glazes

• Measure Carefully: Fine powders like silica, feldspar, and colorants should be weighed accurately—avoid scooping without a dust mask.
• Sieve & Stir Wet: Sieving & stirring glazes while wet is safer than sifting raw powders. This also ensures a smooth, homogenous glaze.
• Small Batches First: If you’re testing a new recipe, make a small batch. If it’s problematic (crazes, leaches metals), you minimize wasted materials and potential hazards.
• Glaze Testing Tiles: Always test new glazes on small tiles or test pieces. Observe how they melt, what surface they produce, and whether they fit your clay body without crazing.

Storing & Disposing of Glaze Materials

• Seal Tightly: Keep powders in lidded buckets or bags within sturdy containers—moisture or accidental tipping can create a dusty mess.
• Label Every Container: Include name, date, and composition. Mystery buckets cause confusion, accidents and waste.
• Dispose of Wastes Properly: Don’t pour leftover toxic glazes down the drain. Let them evaporate into a solid, then check local regulations for hazardous material disposal. Lead-containing or highly toxic wastes should go to a certified disposal facility.
• Clean Water Disposal: If your rinse water has only small amounts of common clay or fluxes, it’s typically safe to let it settle, then pour off clear water. But if in doubt—especially with colorants—treat as hazardous or consult local guidelines.

Firing Safety Considerations

• Ventilation: Glazes can release fumes when fired. If you fire indoors, a kiln ventilation system is recommended.
• Avoid Overfiring: A glaze that runs too hot can release more fumes, overflow onto shelves, or volatilize certain metals.
• Personal Protection: Don’t peer into a hot kiln without proper eye protection (infrared goggles) Kilns at high temperature emit both ultra violet (UV) and infrared (IR) light. While sunglasses may protect against UV exposure, they do not block IR light. One must use glasses or welding goggles that are certified to block both UV and IR light. Wear dry kiln gloves made of insulated leather or Kevlar.
• Restrict Access: Only people trained in the safe maintenance and operation of kilns should have access. Keep kids & pets away from active kilns.

References & Further Reading

• Clay Studio Safety  by Vince Pitelka
• An Overview of Glaze and Glazing Safety  by William M. Carty and Hyojin Lee
• Alfred Grinding Room Raw Materials Orientation 
• Eye Health for Potters  by Glenn Woods with Laura T. Muller, MD
• OSHA: Silica Hazards 
• Princeton Ceramics Safety Guide