Verdict
AMACO Cosmos glazes are the easiest way we found to get a crystal surface from a home electric kiln at cone 5 to 6. AMACO sells eight colors in pints, four of them new in 2026, and says they fire in a normal medium-speed glaze firing with no special cooling schedule. A controlled cool grows more crystals, but it is optional.
The trade-off is behavior. Every Cosmos color is described by AMACO as fluid or highly fluid, each needs about four coats, and AMACO recommends leaving the inside or back of the piece unglazed. AMACO also says the glazes are food safe "but due to durability" not recommended for food surfaces. That makes Cosmos a line for vases, sculpture, tiles and jewelry, not for mugs. This review is research-based: we compared AMACO's line page, product pages, product sheets and 2026 launch post, and did not fire the glazes ourselves.
For how Cosmos fits next to Potter's Choice, Celadon and the rest of the brand, see our AMACO glazes review.
AMACO Cosmos at a glance
| Spec | AMACO's figure | Where AMACO says it | What it means at home |
|---|---|---|---|
| Line code | CO (Cosmos) | Line page | Search dealers for "CO" plus the number |
| Current colors | 8 | Line page and product sheet | CO-3, 5, 6, 7, 8, 14, 21 and 24 |
| Glaze cone | Cone 5 to 6 | Line page | A standard mid-fire electric kiln works |
| Bisque | Apply to cone 04 bisque, 1,945°F (1,063°C) | Line page | Bisque as you would for most AMACO glazes |
| Coats | 4 (product pages); 3 to 4 generous coats (sheet) | Product pages and sheet | Plan on four full brushed coats |
| Cooling | No special cooling needed; controlled cool adds crystal growth | Line page and sheet | Your normal cone 6 program is the starting point |
| Size | Pint only | Product pages | No gallon or dry mix for dipping |
| Food surfaces | "Yes, but due to durability, these glazes are not recommended for food surfaces." | Line and product pages | Keep Cosmos off insides of mugs, bowls and plates |
Price band: typically $36 to $40 a pint at AMACO's shop and US dealers in October 2026, which is well above Potter's Choice. Check the live price before you buy, and note that CO-7 Solar Flare showed as out of stock on AMACO's shop when we checked.
AMACO prints two sets of cone temperatures. The Cosmos line page lists cone 5 at 2,167°F (1,186°C) and cone 6 at 2,232°F (1,222°C). The Cosmos product sheet lists cone 5 at 2,201°F (1,184°C) and cone 6 at 2,266°F (1,241°C), with the last 200°F (100°C) climbing at 270°F (150°C) per hour. Fire by cone, not by a number, and put a witness cone on the shelf. Our cone chart explains why heating rate changes the figure.
All eight Cosmos colors
These descriptions come from AMACO's own product pages and its 2026 launch post. All eight are applied to cone 04 bisque in four coats.
| Code | Name | AMACO's description | Cone note from AMACO | New in 2026 |
|---|---|---|---|---|
| CO-3 | Event Horizon | Dark, fluid glaze with large crystals and blue and violet highlights | Blue and violet at cone 5; bright gold surface at cone 6 | Yes |
| CO-5 | Dark Matter | Deep, fluid glaze with violet undertones and large rainbow crystals | Large crystals at cone 6; smaller, denser crystals at cone 5 | Yes |
| CO-6 | Supernova | Highly fluid creamy white translucent glaze with a surface "like frost on a window" | Designed for cone 5; can fire to cone 6 | No |
| CO-7 | Solar Flare | Highly fluid light brown, opaque and glossy with iridescent crystals | Best at cone 6; can fire to cone 5 | No |
| CO-8 | Dark Star | Fluid dark matte with iridescent crystals "like a beetle shell"; breaks translucent | Best at cone 6; can fire to cone 5 | No |
| CO-14 | Solar Rainbow | Highly fluid dark gloss with iridescent rainbow crystals; breaks translucent | Best at cone 6; can fire to cone 5 | No |
| CO-21 | Galactic Glacier | Highly fluid light blue; crystals flash pink, violet and silver | Tiles shown at cone 5 and 6; frosty blue to periwinkle as it flows | Yes |
| CO-24 | Blue Starlight | Highly fluid dark royal blue with delicate crystals | Tiles shown at cone 5 and 6 | Yes |
Two colors have their own pages on this site: AMACO Supernova and AMACO Dark Star. This page covers the line as a whole.
What happened to Mars Crystal?
CO-13 Mars Crystal, which AMACO describes as a highly fluid dark brick red glaze with silvery iridescent crystals, appears on an earlier AMACO Cosmos sheet but not on the current line page or the current eight-color sheet. Its single product page is still live, and dealers such as Clay-King still list it. We found no discontinued notice from AMACO, so the honest status is "dropped from the current line, still sold while stock lasts." Do not build a palette around it.
How Cosmos glazes grow crystals
AMACO calls Cosmos microcrystalline: the crystals form straight from the jar during an ordinary cone 5 to 6 firing. That is different from classic crystalline glazes, which need a hold during cooling to grow large crystal fans. If you want that kind of work, read our crystalline glaze guide first; Cosmos is the shortcut, not the same thing.
Temperature changes the look more than with most glazes. Event Horizon grows larger crystals at cone 5 and turns brighter gold at cone 6, while Dark Matter grows its biggest crystals at cone 6. AMACO's sheet says firing temperature affects crystal size and appearance and asks you to test. It also notes that crystals form on both horizontal and vertical surfaces, but vertical surfaces encourage running.
A controlled cooling schedule is the optional extra. AMACO links its cooling schedule from the product sheet and says it increases crystal growth. If your kiln has a programmable controller, you can add it later, once you have seen the plain result.
How to apply Cosmos glazes
AMACO sells Cosmos only in pints and gives coat counts rather than dipping instructions, so plan to brush. These steps follow AMACO's product pages and sheet.
- Bisque fire the piece to cone 04, as AMACO specifies, and wipe off dust with a damp sponge.
- Stir the pint well, then brush four full coats (the sheet allows three to four generous coats). Let each coat dry before the next.
- Stop the glaze about half an inch above the foot. More coats mean more crystals and more running, which AMACO shows on its two, three and four coat test tile.
- Leave the inside or back of the form unglazed. AMACO says this lets the glaze off-gas and avoids pinholing and blistering.
- To catch runs on a vertical form, add horizontal texture near the base, or put a stable glaze such as a Celadon on the lower part, as AMACO suggests.
- Set the piece on a drip tray or soft brick, then fire to cone 5 or 6 at a normal medium speed.
- Fire a test tile with each new batch number. AMACO says raw material variation can change results.
If you must glaze both inside and outside, AMACO publishes an "Up Down" firing program on its website for that case. We do not reprint it here; use AMACO's current version.
A drip tray costs far less than a kiln shelf. Coat shelves with kiln wash as well, and keep Cosmos pieces away from other work on the same shelf.
Firing Cosmos in a home kiln
A standard medium-speed cone 6 program is AMACO's baseline. Load Cosmos pieces on their trays, leave space around them, and place a witness cone where you can see it. Fluid glazes punish over-firing first, so a kiln that runs hot needs checking before you trust it with a pint of crystal glaze.
Follow your kiln maker's clearance and ventilation rules every time. A glaze firing heats the kiln case and the room, and the lid and peepholes get hot enough to burn.
Cosmos on light and dark clay
AMACO fired the tiles on its Cosmos sheet on its No. 11 A-Mix White Stoneware, and shows Event Horizon at cone 5 on No. 16 White Chocolate. For other clays it publishes little. The one direct statement is for Dark Matter, which AMACO says stays "dark, even on light colored clays, and nearly black on dark clays."
Three colors, Dark Star, Solar Rainbow and Supernova, are described as translucent or breaking translucent, so the clay body will show where the glaze thins. AMACO does not publish dark clay tiles for them. If you work on a brown or red body, fire a tile first.
Layering Cosmos glazes
AMACO's published layering for Cosmos is short. Its product sheet shows Supernova over six Velvet underglazes: V-317 Coral, V-343 Chartreuse, V-389 Flame Orange, V-386 Electric Blue, V-308 Yellow and V-379 Ultra Violet. That works because Supernova is a creamy translucent white, so the color below shows through the frost. Our AMACO Velvet underglaze review covers those colors.
The other published pairing is defensive: a stable glaze such as a Celadon on the lower part of the piece to slow the run. We found no AMACO pages layering two Cosmos glazes together or putting Cosmos over Potter's Choice. Any glaze stacked under a fluid crystal glaze adds thickness and run risk, so test on a tile with a tray under it.
Food surfaces: what AMACO's label says
AMACO's wording on every Cosmos page is: "Yes, but due to durability, these glazes are not recommended for food surfaces." Keep Cosmos off the inside of mugs, bowls and plates, and off lips and rims. Whether any glaze is safe on your own pots depends on firing to the stated cone on a suitable clay and on testing; see our food safe glaze guide.
What Cosmos does well
- Crystals without a special program: AMACO says a normal medium-speed firing works.
- Two looks from one jar: Event Horizon and Dark Matter change clearly between cone 5 and 6.
- Clear instructions: AMACO prints coats, bisque cone, foot clearance and the unglazed-side advice on each page.
- A range of colors: cream, brown, blue, violet-black and rainbow, all in one compatible cone range.
Weak points
- Every color runs: drip trays are not optional.
- Not for food surfaces: by AMACO's own label.
- Four coats from a pint: one pint covers fewer pieces than a glaze needing two or three coats.
- Bare inside or back: limits the forms you can glaze fully without AMACO's special program.
- Pint only and higher priced: no dry mix and no gallon.
Who should buy Cosmos, and who should skip it
Buy Cosmos if you fire at cone 5 to 6, make decorative vessels, sculpture, wall tiles or jewelry, and want crystal effects without learning a crystalline firing schedule.
Skip Cosmos if you mostly make functional ware, dislike cleaning glaze off shelves, fire only at low fire, or need dipping glaze in bulk.
Starter color: CO-3 Event Horizon
Event Horizon is picked because it shows the line's biggest strength: one jar gives blue and violet crystals at cone 5 and a gold surface at cone 6, so a single pint teaches you how your kiln fires. AMACO shows it on both A-Mix White Stoneware and White Chocolate clay.
- Cone: 5 to 6, on cone 04 bisque
- Coats: 4
- Look: dark, fluid, large crystals; gold at cone 6
- Size: pint
- Label: food safe per AMACO, not recommended for food surfaces
Pros
- Two distinct results by cone
- New 2026 color with maker photos at both cones
- Dark base hides small application marks
Cons
- Fluid, needs a tray
- Dark result may hide carved detail
Who should skip it: anyone who wants a light or pastel crystal surface; choose Supernova or Galactic Glacier.
Starter color: CO-6 Supernova
Supernova is picked because it is the one Cosmos color AMACO says is designed for cone 5, and the one with published layering over underglaze. Its creamy translucent frost works over Velvet colors, which opens up painted designs under a crystal surface.
- Cone: designed for 5, can fire to 6; cone 04 bisque
- Coats: 4
- Look: creamy white, translucent, frosty crystals
- Size: pint
- Label: food safe per AMACO, not recommended for food surfaces
Pros
- Layers over six named Velvet underglazes
- Suits cone 5 kilns
- Light color shows texture
Cons
- Highly fluid
- Cream rather than bright white
Who should skip it: potters who want a pure white or an opaque cover over a dark clay.
Alternatives
For a crystal look on pieces that need a dinnerware label, Mayco's SW-156 Galaxy is a cone 6 charcoal gloss with white, orange and blue crystals that Mayco labels dinnerware safe; it still needs crystals kept off the lower third of tall pieces. See our Mayco Stoneware review.
For true large-crystal work, plan for a controller and a crystalline firing schedule instead of a ready-made line.
Safety notes
Read AMACO's SDS for each color before use. Brush, do not spray, unless you have a spray booth and the protection the SDS names. Wet-clean glaze spills and dust instead of sweeping, because glaze and clay dust contain silica. If you grind glaze drips off shelves or pot feet, wear eye protection and a NIOSH-approved respirator, and wet the area first.
Sources: AMACO Cosmos (CO) line page; AMACO product pages for CO-3 Event Horizon, CO-5 Dark Matter, CO-6 Supernova, CO-7 Solar Flare, CO-8 Dark Star, CO-13 Mars Crystal, CO-14 Solar Rainbow, CO-21 Galactic Glacier and CO-24 Blue Starlight; AMACO Cosmos product sheets (current eight-color sheet and earlier sheet); AMACO blog "New Cosmos Glazes for 2026!"; Clay-King Cosmos listing for stock and price band. Specs checked October 2026.