A raku glaze is built for one of the harshest firings in pottery: a fast climb to a low-fire temperature, a pull from the kiln with tongs while the pot is glowing, and a smoky trip into a reduction can. Regular glazes can crack, craze or go dull under that treatment. Raku glazes are designed to melt fast and to react with smoke and reduction to give crackle, copper flash and iridescent colors.
Home Pottery HQ is a research site. We have not fired these glazes ourselves; the details below come from glaze maker instructions, dealer listings and published references named under Sources. For the full firing process, see our raku firing guide.
What makes raku glazes different
Three things set raku glazes apart from the jars you use in an electric kiln.
- Fast, low melting. Raku glazes are formulated to mature at low-fire temperatures in a short firing. Mayco fires its raku line to cone 06, about 1,850°F (1,010°C), with a 5-minute hold; Spectrum recommends a peak of 1,700°F to 1,750°F (927°C to 954°C). Many raku recipes rely heavily on boron frits to melt that quickly.
- Effects that need reduction. Copper, crackle and luster effects develop when the hot pot meets the smoke and low oxygen inside the reduction can. Fired in a normal oxidizing kiln, the same glaze often looks plain.
- A porous result. Seattle Pottery Supply states that raku glazes do not form a full glass and are therefore not food safe or watertight. The clay body under them is also open and porous.
Types of raku glazes
Crackle glazes
Clear and white crackle glazes are the classic raku look. The glaze cracks from thermal shock as the pot cools, and smoke from the reduction can blackens the cracks, leaving a dark line pattern. Examples include Mayco RK-103 White Crackle and Seattle Pottery Supply RG155 Clear Crackle and RG132 White Crackle.
Copper and metallic lusters
Copper-bearing raku glazes can flash red, gold, purple and blue in heavy reduction. Mayco says thinner coats bring out more metallic effect on its metallic glazes. Examples include Mayco RK-101 Copper Metallic, RK-105 Copper Penny and RK-107 Oil Slick, and SPS RG147 Copper Luster.
Matte and patina glazes
Matte raku glazes, such as Mayco RK-106 Peacock Matte or SPS RG130 Pipe Patina, give dry, mottled surfaces with turquoise, green and copper tones instead of a bright luster.
Naked raku and resist
Naked raku uses a resist slip and a glaze layer that peel off after firing, leaving smoke lines and patterns on bare, burnished clay. Mayco notes that its Fundamentals underglazes can be used as a background color before burnishing for horsehair or feather raku.
Regular low-fire and other glazes
Ceramic Arts Network notes that many low-fire glazes, and even some high-fire glazes used in layers or as slips, can be raku fired. Results are less predictable, and underglaze colors can fade in reduction, so test first.
Raku glazes compared
| Line | Form | Maker's firing guidance | Coats | Labeling |
|---|---|---|---|---|
| Mayco Raku (RK-100 to RK-107, six colors) | Liquid, pint | Cone 06 (1,850°F / 1,010°C), hold 5 minutes; reduce about 20 minutes | 2 to 3 (2 for RK-106 and RK-107) | Not food safe; RK-103 is AP, others CL (not for children under 12) |
| Spectrum Raku series (for example 853, 873, 882) | Liquid, pint | 1,600°F to cone 06; recommended peak 1,700°F to 1,750°F; cool to about 1,600°F before pulling; at least 20 minutes in the can | Formulated for brushing; not stated per color on the listings we checked | Lead-free; see note below |
| Seattle Pottery Supply RG line (about 27 glazes plus RB100 Raku Base) | Dry powder, by the pound | Low fire, cone 08 to 06 on the RG155 listing | 2 to 3 brushed coats or a 3 to 5 second dip | "Not food safe or watertight"; Prop 65 warning for quartz and lithium carbonate |
Source conflict: one dealer listing for Spectrum Raku Red describes it as lead-free, non-toxic and safe for food contact, while another dealer's listing for Spectrum Cobalt Blue Raku says it exceeds copper limits and is non-toxic only once fired. Mayco and Seattle Pottery Supply label their raku glazes not food safe. Because raku ware is porous and the glazes are fired fast, we treat all raku pieces as decorative.
Prices in October 2026 ran from about $8 to $27 per pound for Seattle Pottery Supply's dry raku glazes and about $15 to $30 per pint for liquid raku glazes at US dealers; check the live price.
How to apply raku glaze
- Start with bisqueware made from a clay that can handle thermal shock. Seattle Pottery Supply recommends raku clays for its glazes; our raku clay guide explains why open, groggy bodies survive better. Bisque first, as in our bisque firing guide.
- Wipe the bisque with a damp sponge to remove dust.
- Decide what stays bare. Mayco says not to glaze the inside or bottom of the piece. Bare clay turns black in reduction, which many potters use as a design element.
- Stir the glaze well. For dry powders, Seattle Pottery Supply suggests about 11 oz of water per pound of glaze for dipping consistency.
- Brush 2 to 3 coats, alternating brush direction and letting each coat dry, or dip for 3 to 5 seconds. Go thinner on metallic glazes when the maker says so.
- Let the glaze dry completely before the firing. Damp glaze can pop or crawl in a fast raku climb.
General brushing and dipping methods are in our guide on how to glaze pottery.
What the glaze needs from the firing
Each maker gives its own temperatures, so follow the label for the glaze you use. Mayco fires to cone 06 with a 5-minute hold, then puts the ware straight into a lidded metal can with combustibles for about 20 minutes. Spectrum recommends a 1,700°F to 1,750°F peak, letting the kiln cool to about 1,600°F before the transfer, and at least 20 minutes in the reduction bin. After cooling, Mayco suggests cleaning with water and a scouring pad to bring up the luster. The kiln, reduction chamber and timing are covered in our full firing guide linked above and in our raku kiln guide.
Making your own raku glaze
Homemade raku glazes are usually a fast-melting base, often mostly boron frit, with a little clay to keep the glaze suspended and a colorant such as copper carbonate or cobalt. If you want to mix your own, start from a published, tested recipe or a dry base such as Seattle Pottery Supply's RB100 Raku Base, and add colorants in small, measured test batches.
Mixing dry raku glaze means handling frit, silica and metal colorants. Read the SDS for every material, wear a NIOSH-approved respirator while weighing and mixing powders, and clean up with water. Our glaze materials guide covers the hazards of the common colorants.
Why raku copper colors change over time
Ceramic Arts Network notes that copper flash and luster finishes can fade within a few years as the copper re-oxidizes in air. Sealing the surface slows this but changes the look, and a coating on the outside alone does not stop moisture getting in from the inside. Expect bright copper pieces to soften in color over time.
Common raku glaze mistakes
- Glazing too thickly. Heavy coats can run, mute metallic effects or crawl in a fast firing.
- Pulling pots too early. Raku glaze should look melted and glossy before the transfer; Spectrum's peak guidance helps.
- Weak reduction. A can that is too large or opened too soon gives patchy color.
- Using a dense stoneware or porcelain body that cracks from the thermal shock.
- Expecting the same result every time. Raku varies from pot to pot by nature.
- Using raku pieces for food or drink.
Safety with raku glazes
Mayco's safety guidance for its raku line calls for fire-protective clothing, fireproof gloves and eye protection, turning off the power to an electric kiln before opening it or reaching in with tongs, and doing the reduction outdoors because of flames and smoke. Spectrum adds a respirator and a fire extinguisher. Follow your kiln maker's instructions, local fire code and propane safety rules for gas raku kilns.
Mayco also calls for a NIOSH-approved respirator when spraying glaze. Several raku glazes carry health caution labels: Mayco rates most of its raku colors CL (not for children under 12), and Seattle Pottery Supply's listings carry a Proposition 65 warning for quartz and lithium carbonate. Whether raku ware can be used for food is covered on our raku pottery page; our view is decorative use only.
What you need
Beyond the glaze, raku needs a raku kiln, a lidded metal reduction can, long tongs, heat-resistant gloves, a face shield or safety glasses and a respirator for smoke. Our kiln gloves buying guide compares heat-rated gloves, and our pottery respirator guide covers masks for glaze mixing and smoke.
Sources: Mayco raku glaze page (RK-100 to RK-107 instructions, sizes and safety); Seattle Pottery Supply raku glaze collection and RG155 Clear Crackle Raku listing; Spectrum raku glaze listings at Krueger Pottery Supply (853 Cobalt Blue Raku) and The Ceramic Shop (873 Raku Red); Ceramic Arts Network, "Successful Tips and Techniques for Raku Firing"; The Pottery Wheel, "How to Glaze Raku Pottery". Specs checked October 2026.