Frit is a pre-melted glass powder that glaze makers and home potters add to recipes as a reliable melter. If a glaze recipe lists "Frit 3134" or "Ferro Frit 3195", it is calling for one of these factory glasses. This guide explains what frit means in pottery, how it is made, why glazes rely on it, how the common frits differ, and what the maker safety data sheets (SDS) say about handling it.
Home Pottery HQ is a research site. We have not mixed or fired these frits ourselves. The figures below come from supplier listings, frit data published by Digitalfire, and Ferro safety data sheets, all listed under Sources.
What frit means in pottery
In everyday English a frit is any fused, granulated glass mix. In ceramics it has a narrower meaning: a manufactured glass that carries the fluxes (melters) and part of the silica a glaze needs. The Ceramic Shop describes frits as a type of manufactured glass that contains the main parts of a complete glaze.
A frit is not a finished glaze on its own in most cases. It melts well but usually lacks enough alumina and clay to stay put on a vertical pot and to keep the glaze slurry suspended in the bucket. That is why recipes pair frit with kaolin, silica and other glaze materials.
How frit is made
- The maker weighs out raw materials, often including soluble ones such as borax or soda ash, plus silica and other oxides.
- The batch is melted in a furnace until the ingredients fuse into a single glass.
- The hot glass is quenched, usually by pouring it into water, which shatters it into small pieces.
- The pieces are dried and ground into the fine powder potters buy by the pound.
Because the ingredients are already melted together once, the frit behaves like glass in the kiln. It softens gradually instead of going through the sudden reactions raw minerals can show.
Why potters use frit instead of raw materials
It makes soluble fluxes usable
Some of the best melters, especially boron and sodium compounds, dissolve in water. In a glaze bucket that causes problems: the dissolved part soaks into the bisque, migrates as the pot dries and can change the glaze over time. Fritting combines these materials with silica so they become far less soluble.
It melts smoothly at low temperatures
Digitalfire reports that glazes made with frits melt better than glazes of the same chemistry built from raw materials, with fewer defects and a smoother surface. Frit 3134, for example, is listed as melting across roughly 1,450°F to 1,600°F (788°C to 871°C). That makes frit the backbone of most low-fire glazes, and a helper in many cone 6 recipes.
It is more consistent
Natural minerals vary from mine to mine and from year to year. A frit is made to a target chemistry, so a recipe that worked last year has a better chance of working this year. This was one reason studio potters moved toward boron frits when supplies of Gerstley Borate became uncertain.
It reduces the risk from toxic ingredients
Wikipedia and Digitalfire both describe fritting as a way to turn soluble or toxic ingredients, historically lead, into a more stable glass. The four common frits in this guide contain no lead in their published analyses, but lead-bearing frits such as Ferro 3304 still exist, so check the label and SDS. Fritting reduces handling risk; it does not make a finished glaze food safe on its own.
Common frits for home potters compared
Ferro Corporation's frit business now trades as Vibrantz Technologies, so bags and dealer listings may show either name. Some numbers also carry a suffix, such as 3124-2 and 3110-2. The chemistry below is the oxide analysis Digitalfire publishes for each frit.
| Frit | Main oxides (approx.) | Expansion | Typical use | Listed equivalents |
|---|---|---|---|---|
| Ferro 3134 | B2O3 22.8%, CaO 19.5%, Na2O 10.1%, Al2O3 2.0% | High (9.47) | General melter, boron source from cone 06 to 10 | Fusion F-12, Hommel 14, Pemco P-54 |
| Ferro 3124 | B2O3 13.7%, CaO 14.3%, Al2O3 10.0%, Na2O 6.4% | Medium (7.94) | Low-fire clear base with 10% to 20% kaolin; boron and calcium in cone 3 to 6 glazes | Fusion F-19, GF-113, Pemco P-311 |
| Ferro 3195 | B2O3 22.6%, Al2O3 12.0%, CaO 11.4%, Na2O 5.7% | Medium (7.16) | Low-fire base (85 frit to 15 kaolin at cone 04); boron in stoneware glazes | Fusion F-2, GF-115, Pemco P-67 |
| Ferro 3110 | Na2O 15.2%, SiO2 69.8%, CaO 6.3%, B2O3 2.6% | Very high (10.08) | Sodium source instead of feldspar; crackle and crystalline glazes | Fusion F-75, GF-134, Pemco P-1V04 |
Research note: expansion figures are Digitalfire's calculated coefficients and are only useful for comparing frits with each other. Frits listed as "equivalent" have similar, not identical, chemistry, so a swap still needs a test tile.
Two practical points stand out. Frits 3134 and 3110 have high expansion, which pushes a glaze toward crazing (a fine crack network) on many clay bodies; see our glaze crazing guide. Frits 3124 and 3195 contain more alumina, so they make stiffer, more stable melts and are closer to a complete glaze.
How frit is used in glaze recipes
Low-fire glazes are often mostly frit. Digitalfire describes a transparent cone 04 base of 85% Frit 3195 and 15% kaolin, and notes that Frit 3124 needs only about 10% to 20% kaolin to act almost as a complete low-fire glaze. Our low fire glaze guide covers the commercial side of that range.
At cone 6, frit usually plays a supporting role. A few percent to a few tens of percent of a boron frit lowers the melting point of a feldspar and whiting glaze and smooths the surface. Raku glazes lean hard on frit for the same reason: they must melt in minutes. Our raku glaze guide explains that firing.
Frits are not plastic, so a recipe heavy in frit settles fast in the bucket. Kaolin or a small addition of a gum such as CMC or VeeGum helps keep it suspended and helps the dry glaze stick to the bisque. Mixing steps are in our guide to mixing glaze from powder.
Do not swap frits one for one just because a supplier is out of stock. Frit 3134 has about one fifth the alumina and roughly 1.7 times the boron of Frit 3124, so the same weight gives a very different melt. Use glaze calculation software or a supplier substitution chart, then test.
Frit versus Gerstley Borate
For decades, the natural mineral Gerstley Borate was the cheap way to get boron into a glaze. It melts suddenly, gels in the bucket and loses close to 30% of its weight as gas in the kiln. Boron frits soften across a wide range instead, give smoother slurries and stay consistent, though some potters miss the visual variation Gerstley gave. Our glaze materials guide covers Gerstley Borate and its substitutes.
Are frits soluble?
Frits are sold as insoluble, and The Ceramic Shop's listing describes them that way. Digitalfire disagrees in part: it reports that some frits are slightly soluble, that this can cause glazes to thicken or grow crystals in long storage, and that frit quality has varied between batches. The practical takeaway is to mix frit glazes in batches you will use within a few months and to stir and check thickness before each session.
Common mistakes with frit
- Treating frit numbers as interchangeable. Each number is a different glass.
- Leaving out the clay. A glaze with no kaolin settles hard and powders off the pot before firing.
- Buying a frit without reading its SDS. Lead-bearing frits exist; read the label and choose lead-free frits from a pottery supplier.
- Assuming a frit glaze is food safe. Fritting helps stability, but leaching depends on the whole recipe, the clay and the firing.
- Sweeping up spilled frit. Glass and silica dust should be cleaned wet.
Safety when handling frit
Read the maker's SDS for each frit before you open the bag. Mix dry frit and other glaze powders only while wearing a NIOSH-approved respirator rated for fine dust, clean spills with a wet sponge or mop (never dry sweep), and keep food and drink out of the mixing area.
The Ferro SDS for Frit 3134 (issued 1998) says prolonged contact with frit dust can irritate the eyes and skin and that high dust levels irritate the respiratory tract; it calls for a NIOSH-approved dust respirator as needed. The Ferro SDS for Frit 3195 (revision 2, 2009) lists it as a skin, eye and respiratory irritant, notes borates among its components, and says chronic overexposure to borosilicate frit dust may cause coughing, wheezing and impaired lung function.
Frit is usually mixed with silica and clay, which add crystalline silica dust to the room. Our clay dust safety guide covers wet cleaning and ventilation in more detail.
Food safety is never guaranteed by a single ingredient. If you want to make mugs and bowls, read what the glaze maker labels, fire to the stated cone, and consider leach testing; our food safe glaze guide explains the steps.
Buying and storing frit
US pottery suppliers sell frit by the pound, and many offer lower per-pound rates on larger bags. At The Ceramic Shop, the four common frits above were listed at roughly $8 to $10 per pound for small quantities in October 2026; check the live price. Store frit sealed and dry, label the bag with its number, and keep the SDS with it.
What you need
To work with frit at home you need a scale that reads to a tenth of a gram, sealed containers, a sieve, and a properly fitted respirator. Our pottery respirator buying guide compares masks for mixing dry materials, and our pottery supplies guide lists where to buy frits and other raw materials.
Sources: The Ceramic Shop frit category and Frit 3110 listing (Vibrantz/Ferro); Digitalfire reference pages for Frit, Ferro Frit 3134, 3124, 3195 and 3110 and Gerstley Borate; Ferro Corporation SDS for Frit 3134 (1998) and Frit 3195 (rev. 2, 2009); Wikipedia, Frit; Holst Porzellan, Frits. Specs checked October 2026.