Seaweed glaze combinations show up in almost every AMACO layering gallery, because PC-42 Seaweed is a deep green that flows and breaks brown over texture. This page lists the combinations AMACO has published with Seaweed, which glaze goes on top in each, the coats and cones AMACO states, and how to keep a runny glaze off your kiln shelf. We do not describe fired results: we have not fired these glazes, and AMACO's photos are the reference.
General layering technique is covered in our AMACO glaze layering guide, so this page sticks to Seaweed. Research is from AMACO's product page, layering database, blog posts and a tutorial, plus dealer listings, checked in October 2026.
What AMACO PC-42 Seaweed is
AMACO describes Seaweed as "a fluid, deep green glaze that layers beautifully with a variety of Potter's Choice glazes". It "breaks brownish over texture and becomes more fluid with thickness", and AMACO adds a direct warning: "Pay attention to application thickness so the glaze does not flow onto kiln shelves during firing."
- Code: PC-42 (Potter's Choice)
- Glaze fire: Cone 5, 2,167°F (1,186°C), to cone 6, 2,232°F (1,222°C), per AMACO
- Bisque: Cone 04, 1,945°F (1,063°C)
- Opacity: Opaque mark on AMACO's page
- Sizes: Pint and gallon, plus a dry dipping mix; a pint is typically about $20 to $30 at US sellers in October 2026
- Marks shown: CL (cautionary label) and opaque
The Ceramic Shop lists cone 5 as 2,201°F and cone 6 as 2,266°F, figures tied to a different heating rate. We use AMACO's figures above. Both describe the same cone 5 to 6 range.
Is AMACO Seaweed a runner?
Yes, by AMACO's own words. Its Magic Forest post says "Seaweed is a runner, so keep it near the top of the piece and let it flow a little", and its customer-favorites post says Seaweed "will get runny when fired hotter". The product page adds that it gets more fluid as it gets thicker. Three things push it to run: more coats, a hotter firing, and a fluxing glaze underneath.
AMACO's published Seaweed combinations
AMACO names combinations top glaze first, and in nearly every Seaweed entry we found, Seaweed is the top glaze. The database pages blocked our research tools, so names and order come from AMACO's entry titles, and coats and cones come from AMACO blog posts where it gave them. Open each entry on amaco.com for the photo and notes.
Seaweed on top
| Combination (top over base) | Coats | Cone | AMACO source |
|---|---|---|---|
| PC-42 Seaweed over C-1 Obsidian | Seaweed 2; Obsidian 2 to 3 | 5 or 6 | Customer-favorites blog |
| PC-42 Seaweed over C-57 Mulberry | Not stated | 5 to 6 | Customer-favorites blog (named as the classic) |
| PC-42 Seaweed over PC-21 Arctic Blue | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-33 Iron Lustre | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-31 Oatmeal | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-40 True Celadon | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over C-11 Mixing Clear | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over C-23 Ice | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over C-36 Iron | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-25 Textured Turquoise | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-56 Ancient Copper | See entry | 5 to 6 | Layering database |
| PC-42 Seaweed over PC-44 Sage | See entry | 5 to 6 | Layering database |
AMACO's notes on the Obsidian pairing are the most complete: two coats of Seaweed over two to three coats of Obsidian, cone 5 or 6, and Obsidian is opaque and "works on most clays". Arctic Blue appears with Seaweed often enough to have its own page: AMACO Arctic Blue.
Seaweed over flux and specialty bases
AMACO's database also lists Seaweed over several Potter's Choice Flux (PCF) glazes and other specialty bases: PCF-75 Moss Mist, PCF-54 Flux Blossom, PCF-3 Midnight Run, PCF-19 Cirrus Flow, PC-10 June Bug, PC-16 Purple Crystal and PC-38 Iron Yellow. A flux base makes the glaze above it move more, so these are the pairings most likely to reach the foot. Start them with one coat less of Seaweed than you would over Obsidian.
Seaweed as the base
We found one AMACO entry with Seaweed underneath: PC-44 Sage over PC-42 Seaweed. With a fluid glaze at the bottom of the stack, the whole layer tends to slide, so leave extra bare clay above the foot.
Seaweed as an accent: dots and stripes
AMACO also uses Seaweed in small amounts, where its flow becomes the decoration.
- Magic Forest: two coats of PCF-74 River Birch, then one coat of PC-21 Arctic Blue, then Seaweed dots or stripes near the top, fired to cone 6. AMACO notes that on horizontal surfaces "the Seaweed won't get as much movement". See AMACO River Birch.
- Peacock Feather tutorial: three coats of PC-32 Albany Slip Brown, then Seaweed applied as dots with a slip trailer bottle, on A-Mix White Stoneware at cone 5.
Dots and stripes need a fine-tip squeeze bottle; our slip trailing guide covers the tools.
How many coats of Seaweed to use
In AMACO's layered examples, Seaweed goes on at two coats over a base of two to three coats. Dealer advice for Seaweed alone is heavier: The Ceramic Shop says "three thick coats", leaving "a little room at the foot", and warns that a thin coat looks "splotchy and incomplete". Use two coats in a stack and three only when Seaweed is the only glaze.
- Pick a combination and note which glaze is the base.
- Glaze a vertical test tile with texture, stopping Seaweed partway down.
- Wax the foot and leave at least the lower half inch of the pot bare.
- Brush the base coats over the whole glazed area and let them dry.
- Brush Seaweed on the upper part, heaviest at the rim.
- Set the piece on a cookie or in a catch tray, then fire to the cone listed.
Seaweed on light and dark clay
AMACO's Seaweed examples are on A-Mix White Stoneware, and AMACO does not publish how Seaweed looks on dark clay. Its breaking brown over texture may read differently on a red or brown body, so fire a tile on your own clay before glazing a set.
Keeping Seaweed off the kiln shelf
Seaweed's run is the most common reason a Seaweed pot fails. Keep it near the top, use fewer coats near the bottom, and never fire a Seaweed piece straight on a bare shelf. A bisque cookie slightly wider than the foot, a catch tray for test tiles, and shelves coated with kiln wash protect the kiln. If your kiln fires hot, AMACO's own advice is that Seaweed runs more.
Food safety
When we checked AMACO's PC-42 page in October 2026, it showed a CL mark and no Food Safe seal. The Ceramic Shop lists Seaweed as food safe, and other dealers repeat AMACO's line that tableware makers "must test all finished ware". AMACO also says its dry dipping version carries different health labels from the brushing glaze. We go by the maker's page.
Read the label on the jar you buy and AMACO's SDS. Treat every Seaweed combination as untested for food contact, keep test pairings on the outside of mugs, and see our food safe glaze guide. If you mix the dry dipping version, wear a NIOSH-approved respirator, mix wet, and clean up with a damp sponge, never a broom.
Common mistakes
- Brushing Seaweed all the way to the foot.
- Using three thick coats in a layered stack.
- Putting Seaweed over a flux glaze without testing it.
- Assuming a dipping bucket layers like a brushing pint; AMACO says dry dipping glazes "can be difficult to layer".
- Copying a photo fired on white stoneware onto dark clay without a test.
Honey Flux is the other popular AMACO layering glaze; see Honey Flux glaze combinations. For pairings across many brands, see our glaze combinations guide.
What you need
You need a pint of PC-42 Seaweed, a base from the tables, wax resist, a soft brush, a slip trailer if you want dots, bisque cookies and kiln-washed shelves. Our Potter's Choice review compares the base glazes and their sizes.
Sources: AMACO product page for PC-42 Seaweed (shop.amaco.com); AMACO layering database entry titles for PC-42 pairings (amaco.com, Resources, Layering); AMACO blog posts "Customer-Favorite AMACO Glaze Combinations to Try" and "Try Something New: Magic Forest Glaze Combination"; AMACO tutorial "Peacock Feather Effect"; The Ceramic Shop and Clay Art Center PC-42 listings (coats, cone figures and dealer food labels). Research-based, not hands-on; no test tiles fired. Specs checked October 2026.