If you've spent any time in the ceramics world, you've probably seen the term "food safe" on glaze labels — including ours. But what does it actually mean? And why do we add the caveat that you should still test your glazes on your specific clay body? Let us break it down.
Five Glaze Food Safe/Dinnerware Safe Symbol
What we mean when we say food safe
When we label a Five Glaze product as food safe, here's what we're telling you:
- Our glazes are formulated without lead. Lead was commonly used in historical ceramic glazes and is still used industrially, but it has no place in studio ceramics intended for functional ware. We don't use it, full stop.
- Our glazes are chemically formulated to resist leaching — meaning when properly fired, they won't break down and release materials into acidic food or beverages over time.
- Our glazes are durable enough for dishwasher use. A glaze that looks fine fresh out of the kiln but degrades over repeated dishwasher cycles isn't truly food safe in a practical sense. We test for this.
- Our glazes hold up on dinnerware without discoloring or breaking down when in contact with acids like coffee, citrus, or vinegar.
We formulate and test all of our glazes on Ice Man Clay from KY Mudworks at cone 5/6. That's our baseline, and it's where we're confident in these claims.
What food safety actually depends on — and why we can't guarantee it universally
Here's the part that matters, and we want to be honest with you about it: glaze chemistry alone doesn't determine food safety. Application and firing do too.
Research in glaze science confirms what potters have known intuitively for a long time: the underlying chemistry of a glaze matters enormously, but so does how that glaze is fired, how thickly it's applied, and how well it fits the clay body it's on.
A glaze that performs beautifully on one clay body can craze, pinhole, or shiver on another — and any of those defects compromise food safety regardless of how well the glaze is formulated. Crazing (those fine crackle lines in a glaze surface) creates tiny crevices where bacteria can harbor. Pinholes and crawling expose bare clay. Shivering means the glaze is under stress and may flake.
Because we can't control how you apply our glazes, what kiln you fire in, or what clay body you're using, we can't make a blanket food safety guarantee for every pot you make with Five Glaze. What we can do is give you the tools and knowledge to test it yourself.
How to know if your glaze is performing well
Before you put a piece into regular food use, look it over carefully:
Crazing — Fine lines or a crackle pattern in the glaze surface. This is a glaze-fit issue, meaning the glaze and clay body are expanding and contracting at different rates. Crazed glaze is not ideal for functional ware.
Pinholes — Tiny holes in the glaze surface. These can result from applying glaze too thinly, from glaze applied over contaminated bisqueware, or from underfiring. Pinholed glaze should not go into food use.
Shivering — Small flakes of glaze popping off the surface, often at edges. Like crazing, this is a fit problem — but in the opposite direction. The glaze is too tight for the clay body.
Crawling — Glaze that has pulled away from the clay surface, leaving bare patches. Often caused by applying glaze too thickly or over dusty bisqueware.
If you see any of these on a piece, set it aside for decorative use only. If you're consistently seeing them with Five Glaze on your clay body, reach out to us — it's worth troubleshooting together.
A note on the broader conversation
The ceramics community sometimes treats "food safe" as a simple yes/no label, and it really isn't. Glaze researchers have pointed out that most of the materials that make up a well-formulated studio glaze — silica, alumina, calcium, magnesium — are of no concern whatsoever in terms of solubility. The real risks historically came from lead and cadmium, which we simply don't use.
The honest answer to "is this food safe?" is: it can be, when properly formulated, properly applied, and properly fired. We've done our part. We'll keep doing it. And we trust you to do yours.
Five Glaze is a cone 5/6 dry batch ceramic glaze company. Our glazes are formulated and tested on Ice Man Clay from KY Mudworks. Questions? Reach out — we love talking glaze