Ceramic Glaze Safety Basics
Glazes come in an extraordinary variety of colors, finishes, and temperature ranges, reflecting the versatility of working with clay. While formulas differ, all glazes are made from three basic components: silica, fluxes, and colorants. Fluxes raise or lower the melting point of silica, allowing the glaze to mature at specific temperatures. Colorants — usually metal oxides — create the final fired color and typically make up less than 5% of the glaze by weight.
The general “Clean = Safe” studio practices outlined in the first section of our Safety guide provide a strong foundation for safe materials handling. The information below expands on safety considerations specific to glazes.
Read Ceramic Glaze Labels
Commercially produced glazes are required by law to list any handling precautions on their labels. This information is essential. Labels will indicate whether a glaze is lead-free, nontoxic, or food-safe, and they will list any special handling instructions. They also specify the intended firing range, which is key to achieving successful results. Working with wet, premixed glazes also greatly reduces — or eliminates — the risk of dust inhalation.
Dry Glaze Safety
Dry glaze materials are extremely fine powders that are weighed, blended, and mixed with water. Handling these powders can expose you to significant amounts of airborne dust.
There are three primary exposure pathways for hazardous materials:
- Absorption through the skin
- Inhalation of dust
- Ingestion through contaminated food or drink
Of these three, inhalation is the most common and most rapidly harmful, which is why Georgies does not sell glazes in dry form or offer lead-bearing glaze ingredients.
If you mix dry glazes in your own studio, wear at minimum a dust mask and latex or nitrile gloves. For frequent use, we strongly recommend a dustproof respirator.
Go Lead-Free
We encourage all ceramic artists to maintain a lead-free studio from the start. Until the 1980s, lead was widely used as a flux in glaze formulas because it produced bright, glossy results. Over the last several decades, the U.S. ceramic industry has transitioned almost entirely to lead-free glazes. Only a few leaded glazes remain on the market, and they should be treated as toxic.
Lead-bearing glazes:
- cannot legally be used in settings where children or vulnerable populations may come into contact with them
- should be avoided by pregnant women, nursing mothers, and women planning pregnancy
- may produce wastewater that is regulated as hazardous waste in some regions
The simplest — and safest — approach is to avoid these glazes entirely.
Other Metals
Even glazes that are free of lead may contain other metals that carry health risks. Compounds of nickel, chromium, cobalt, antimony, manganese, and others are commonly used as colorants and can be hazardous depending on concentration and exposure.
Safest practices include:
- asking what is in the glazes you use
- keeping your work area clean and organized
- avoiding eating, drinking, or smoking while glazing
- washing your hands thoroughly after glazing
Safe Glaze Application Techniques
Glazes can be applied by pouring, dipping, brushing, or spraying.
- Pouring, dipping, brushing: Clean up spills, drips, and splatters promptly before they dry and become airborne dust.
- Spraying: Spraying creates a fine mist by design. Use a spray booth or other containment equipment, and wear appropriate personal protective gear such as respirators and goggles. These measures are strongly recommended — and in some cases required — for safe spraying.
Have Questions About Glazes? We Have Answers!
Glaze Questions FAQ
Can I layer glazes?
Yes you can layer glazes. We always recommend doing a test tile to make sure you are getting the result you want.
How do I choose the right glaze for my project?
Match the glaze cone with the clay cone you have purchased (i.e. if you purchased CC547CT Wonder White Cone 06 clay you’ll want to choose cone 06 low fires glazes)
What’s the difference between low fire and midrange glazes?
Low-fire glazes are fired to cone 06 (~1852° – 2000° F) and mid-range glazes require a higher fire to cone 6 (~2158° – 2266° F).
Why did my glaze run, crawl, pinhole, blister, or craze?
There could be several reasons why – but the main reasons are improper application, incompatible materials, or firing issues.
How do I test a new glaze?
We recommend testing all new glazes on a test tile to make sure you are getting the results you want.
How much glaze do I need for a specific project?
It depends on the size of your project. We recommend one pint per 6-8 mugs (inside and out) when brushing for average coverage. If you naturally apply thick or thin, it may cover less or more.
Do you offer glaze sample sets?
Yes! We offer sample sets in all of our glaze lines.
Are your glazes food safe?
Lots of glazes are food safe, but we have some that aren’t. Please check the website and/or glaze bottle to see if the glaze you are wanting or have are food safe.
How does application thickness affect results?
It can affect color, texture and durability of your ceramic pieces – and can also be a reason for why your glaze is running, pinholing and/or crazing. Each company has different instructors for their glazes, so following the glaze bottle instructions will be the most helpful in how thick to apply the glaze.
Why does my finished piece not match the sample photo?
It could be several reasons including – application thickness, firing schedule, and lighting of the actual photo itself.
Can I use underglaze with any clay?
You can use underglaze with any clay that is in the same firing range (so if an underglaze is cone 06-6 then you could use cone 06 or cone 6 clay) – although the firing results may be different for cone 06 and cone 6.