The Glazes That Defined Architectural Pottery

The David Cressey Phoenix planter retailed for $100 in 1966. Today it sells for up to $10,000. That's a 10,000% appreciation over 59 years, or roughly 8.4% annually - better than most investment vehicles. The specific piece that commands this price features Cressey's volcanic glaze - a textured surface full of crater holes and bubbled eruptions that looked like cooled lava. This wasn't just about rarity. It was about a specific aesthetic that architects specified for Case Study Houses and MoMA featured in its first "Good Design" exhibition alongside Eames furniture.

Here's what made it technically distinct: The glaze contained silicon carbide, an industrial abrasive also used in grinding wheels. During firing, the silicon carbide decomposes at high temperatures (around cone 6-10, or 2232-2381°F), releasing carbon monoxide gas. The gas erupts through the molten glaze surface, creating crater holes and textured surfaces. The timing of this eruption relative to the cooling cycle determines whether you get small pinholes or dramatic volcanic craters.

Manufacturing Context: From Bisque to Volcanic

Architectural Pottery, founded by Max and Rita Lawrence in 1950, operated from Los Angeles initially, later moving to Manhattan Beach. The company existed during a unique window - post-war housing boom, Case Study House program (1945-1966), modernist architecture becoming mainstream residential rather than exclusively commercial. Their pieces appeared in Richard Neutra, John Lautner, Craig Ellwood, and Pierre Koenig houses. MoMA included Architectural Pottery in its 1950 Good Design exhibition alongside Charles and Ray Eames, Alexander Girard, George Nelson.

The production focused on planters - indoor/outdoor vessels that worked with California's indoor-outdoor living philosophy. Materials: bisque clay (unglazed fired clay with matte porous surface), stoneware with various glazes (matte, glossy, volcanic, foam), and later fiberglass. The bisque pieces came in natural terra cotta tones or got coated with matte white glaze that maintained the unglossed aesthetic.

Designers included Lagardo Tackett (whose pieces now sell for significant premiums), David Cressey (sculptor who created the most collectible volcanic-glazed pieces), Malcolm Leland, John Follis, and Paul McCobb (better known for furniture but designed ceramics for AP). Each brought specific glaze preferences. Cressey leaned heavily into volcanic surfaces. Tackett preferred clean bisque or minimal matte glazes.

The company operated until 1984 when a fire destroyed the Manhattan Beach facility. Total production span: 34 years. During that period, they developed what became defining characteristics of mid-century architectural ceramics - emphasizing form and surface texture over decorative painting or traditional glossy glazes.

Glaze Chemistry: The Science Behind Volcanic Surfaces

Volcanic glazes (also called crater, foam, or fat lava glazes) rely on controlled defects. In traditional pottery, these textures indicate firing problems - insufficient glaze maturity, contamination, improper temperature control. Mid-century potters like Lucie Rie and Otto Natzler pioneered treating these "defects" as intentional decorative surfaces.

The basic mechanism: Silicon carbide (SiC) added to the glaze at 2-20% by weight. At high temperatures during firing, oxygen in the kiln atmosphere reacts with silicon carbide:

SiC + O₂ → SiO₂ + CO

The carbon monoxide gas has to escape. If the glaze is still fluid enough, the gas bubbles burst through, leaving craters. If the glaze has started setting, the bubbles get trapped, creating foam texture. If firing continues after crater formation, the glaze can flow back over the craters, creating partially healed surfaces with complex layering.

Other ingredients affecting volcanic texture:

Cryolite (Na₃AlF₆): Aluminum fluoride compound that decomposes during firing, releasing fluorine gas. Creates similar bubbling effects to silicon carbide but at different temperature ranges.

Gerstley borate: Boron-containing flux that can cause bubbling and crawling effects when used in high concentrations. Less predictable than silicon carbide but creates organic, flowing textures.

Firing atmosphere: Reduction firing (limited oxygen) versus oxidation firing (normal oxygen levels) affects how silicon carbide behaves. Reduction amplifies the carbon monoxide production.

The foam glazes that Haeger Pottery popularized in the 1950s-70s used similar chemistry but aimed for consistent foam texture rather than discrete craters. These glazes stayed thick and viscous during firing, trapping gas bubbles throughout the glaze layer. The result looked like frozen soap suds - appropriate given that Haeger marketed some pieces as "foam finish."

Temperature and Timing: The Manufacturing Variables

Cone 6 (2232°F) represents the low end of stoneware firing. Cone 10 (2381°F) goes higher. Most architectural pottery fired in the cone 6-8 range (2232-2305°F) because higher temperatures increased kiln costs and breakage rates. Silicon carbide volcanic effects work across this range but produce different textures:

Cone 6 firing: Silicon carbide begins decomposing but glaze may not be fluid enough for dramatic craters. Results tend toward smaller pinholes and subtle texture.

Cone 8 firing: Better balance - glaze flows more readily, allowing larger craters to form before the glaze sets during cooling.

Cone 10 firing: Maximum fluidity but also maximum risk. The glaze can flow too much, losing the volcanic texture as it self-heals during cooling. Or it can run off vertical surfaces entirely.

Firing schedule mattered as much as peak temperature. A slow ramp to peak temperature gave silicon carbide more time to decompose gradually, potentially creating more numerous but smaller craters. A fast ramp concentrated the gas release into a shorter window, potentially creating fewer but more dramatic eruptions.

The cooling cycle posed its own considerations. Crash cooling (opening the kiln to drop temperature quickly) froze the glaze while still fluid, capturing maximum texture. Slow cooling allowed partial healing as the glaze remained workable longer. Some potters used this strategically - creating craters at peak temperature, then slow-cooling to let the glaze partially flow back over them, creating complex layered surfaces.

Haeger Pottery, operating from Dundee, Illinois since 1871 (originally making bricks, switching to art pottery in the 1930s), produced enormous quantities of volcanic and foam-glazed pieces during the mid-century period. Their pieces show more standardization than Architectural Pottery - the volcanic effects appear more uniform piece to piece because they optimized firing schedules for consistent results. This made economic sense for a company producing hundreds of thousands of pieces annually versus Architectural Pottery's smaller batch production.

Color Development: Metallic Oxides in Volcanic Glazes

The iconic colors of mid-century architectural pottery came from metallic oxide additions to base glazes:

Copper oxide (CuO): Produces blues and greens in oxidation, reds in reduction. The volcanic texture amplifies color variation - copper concentrates in crater pools, creating darker spots against lighter crater walls.

Cobalt oxide (Co₃O₄): Strong blue colorant. Very stable across firing conditions. In volcanic glazes, creates the dramatic blue surfaces that defined pieces like Bitossi Rimini Blu series (Italian, but same technical approach).

Iron oxide (Fe₂O₃): Browns, yellows, oranges depending on concentration and firing atmosphere. In volcanic glazes, iron creates the amber/honey colors common in California pottery. Reduction firing can push iron toward greens and blacks.

Manganese dioxide (MnO₂): Purple-brown tones. Often combined with iron for complex brown-black surfaces. In crater glazes, manganese can create dramatic color breaks between raised and recessed areas.

Rutile (TiO₂ with iron impurities): Creates tan, brown, cream colors with crystalline texture. In volcanic glazes, rutile encourages crystal formation within crater walls, adding another texture layer.

The white and cream matte glazes that Architectural Pottery used extensively contained minimal colorants - just base glaze ingredients (feldspar, silica, clay, limestone) fired to lower temperatures (cone 04-06, 1915-2232°F). These matte surfaces required different technical considerations than volcanic glazes. The goal was smooth, non-glossy finish without any surface texture. Achieving this meant avoiding any ingredients that might cause bubbling, keeping the glaze thin enough to prevent running, and firing to just below full maturity so the glaze doesn't develop gloss.

Bennington Pottery in Vermont developed their signature spatterware glaze in the early 1970s using a spray technique - darker glaze blown over lighter base color. This wasn't chemically different from standard glazes, just applied differently. But it created the mottled, organic look that made Bennington pieces instantly recognizable. The Obama family selected Bennington spatterware for White House use in 2008, triggering renewed collector interest.

Production Economics: Why These Glazes Won

The volcanic and matte bisque finishes that defined architectural pottery had manufacturing advantages beyond aesthetics:

Defect tolerance: Traditional glossy glazes show every imperfection - dust specks, application irregularities, temperature variations across the kiln create visible defects. Volcanic glazes incorporate irregularity as the aesthetic. Small variations piece-to-piece became "handcrafted character" rather than quality control failures.

Reduced labor: Bisque pieces required minimal surface preparation. No glaze application meant no dipping, spraying, or brush application labor. Fire the bisque, maybe apply a single coat of matte white, done. This allowed faster production cycles.

Kiln efficiency: Single firing for bisque pieces versus two firings (bisque then glaze) for traditional ceramics. Every kiln firing costs fuel and time. Eliminating one firing per piece significantly improved production economics.

Material costs: Volcanic glazes used inexpensive industrial materials. Silicon carbide cost pennies per pound as an abrasive compound. Compare to cobalt oxide (expensive) or rare earth oxides used in some traditional ceramic glazes.

Architectural Pottery pieces retailed from $10-100 during the 1950s-60s (roughly $100-1,000 in 2026 dollars). This positioned them as affordable luxury - more expensive than mass-market planters from department stores, but accessible to middle-class homeowners furnishing new tract housing. The glaze choices directly enabled this price point by reducing production costs while maintaining visual distinctiveness.

Gainey Pottery, another major California producer of architectural ceramics, operated from 1950s-1960s primarily. Their glazes followed similar patterns - bisque finishes, matte colors, occasional volcanic surfaces. Pieces now sell for $50-500 depending on size and condition, significantly less than peak Architectural Pottery but still reflecting mid-century collector interest.

Case Study House Integration: Why Architects Specified These Surfaces

The Case Study House program ran 1945-1966, sponsored by Arts & Architecture magazine. Goal: demonstrate that modern residential architecture could be both beautiful and economically practical for post-war middle-class families. Architects included Richard Neutra, Charles and Ray Eames, Craig Ellwood, Pierre Koenig, John Lautner.

These houses incorporated Architectural Pottery pieces for specific reasons beyond just visual compatibility:

Indoor-outdoor flow: California climate and modernist philosophy emphasized dissolving barriers between interior and exterior. Planters needed to work in both contexts. Bisque and matte glazed stoneware handled UV exposure and temperature fluctuation better than glossy glazes that could craze (develop surface cracks) from thermal stress.

Material honesty: Mid-century modern philosophy valorized showing what materials actually were rather than making them pretend to be something else. Bisque clay looked like clay. Volcanic glazes looked like glazed clay with visible texture. No fake finishes, no applied decoration trying to be something it wasn't.

Sculptural form: The planters functioned as architectural elements, not just containers. Large-scale pieces (some 24-36 inches diameter) anchored interior spaces or marked transitions between zones. The minimal surface decoration (bisque or matte color) emphasized form over ornament.

Production alignment: Case Study Houses aimed to prove modern design could be economically viable. Specifying products from companies using efficient production methods aligned with program goals. Architectural Pottery represented accessible modern design, not just expensive custom work.

The MoMA Good Design exhibitions (1950-1955) curated by Edgar Kaufmann Jr. explicitly promoted modern design as democratically accessible rather than elitist. Including Architectural Pottery alongside Eames, Girard, Nelson sent a clear message: modern ceramics belonged in the same conversation as furniture and textiles, and good design was available at middle-class price points.

Contemporary Recognition: The Collector Market Today

The 2024 Monacelli Press book "Architectural Pottery: Ceramics for a Modern Landscape" and concurrent AMOCA exhibition mark formal art historical recognition of the company's significance. Prices reflect this:

David Cressey Phoenix planters: $2,000-10,000 depending on size and glaze Lagardo Tackett designs: $500-3,000 Malcolm Leland pieces: $300-1,500 Unmarked or attributed pieces: $100-500

Condition matters enormously. Chips, cracks, glaze loss significantly reduce value. Original pieces have distinct characteristics - casting seam lines in predictable locations, specific clay body colors, documented shapes from catalogs. Reproductions exist (some companies have attempted to recreate popular designs) but experienced collectors can distinguish them by weight, clay color, glaze application patterns.

Haeger Pottery pieces sell for substantially less - typically $20-200 - because the company produced vastly larger quantities and remained in operation until 2016. Royal Haeger pieces from the 1930s-40s designed by Royal Hickman command premiums ($100-500) but standard mid-century Haeger remains affordable.

Bennington Pottery still operates, producing pieces that follow David Gil's original design aesthetic. Vintage pieces from the 1950s-70s sell for $30-300. The trigger mug (two-finger hole handle) has remained in continuous production since 1953 - one of the longest-running modern design pieces still manufactured to original specifications.

Gainey pieces occupy middle ground - less expensive than Architectural Pottery, more expensive than Haeger. The yellow glaze that Gainey used extensively (a specific warm butter-yellow achieved with iron oxide and rutile) has become signature to collectors.

Technical Documentation: Recipe Information

Specific glaze recipes remain challenging to document because companies treated them as proprietary. However, the basic approaches are well-established:

Volcanic glaze base (cone 6-8):

• Feldspar 40-50%
• Silica 20-25%
• Kaolin (clay) 10-15%
• Whiting (calcium carbonate) 10-15%
• Silicon carbide 2-20% depending on desired effect
• Metallic oxide colorants 2-8%

Matte glaze base (cone 04-6):

• Feldspar 30-40%
• Silica 25-35%
• Kaolin 15-20%
• Barium carbonate or zinc oxide 5-10% (creates matte surface)
• Minimal colorants for white/cream

Foam glaze approach:

• Standard glaze base made very thick/viscous
• Silicon carbide 5-15%
• Fire slowly to encourage even bubble formation throughout glaze layer
• May require multiple coats for full foam effect

Contemporary potters recreating mid-century aesthetic use these base formulas with adjustments for specific clay bodies and kiln characteristics. The technical knowledge hasn't been lost - it's just that demand for volcanic-surface ceramics declined 1980s-2000s as postmodern and minimalist aesthetics dominated. The mid-century modern revival of the past 15 years has brought renewed interest in these glaze techniques.

The Manufacturing Legacy

Architectural Pottery's influence extended beyond its own pieces. The company demonstrated that ceramics could be integral to architectural design rather than just decorative afterthoughts. This spawned numerous California pottery companies following similar approaches - Heath Ceramics (still operating, now owned by Robin Petravic and Catherine Bailey, focused on tableware but maintaining mid-century aesthetic), Gladding McBean (architectural terra cotta since 1875, expanded into decorative ceramics mid-century), various smaller studios.

The glaze aesthetic - bisque, matte, volcanic, foam - became shorthand for "California modern" or "West Coast style." East Coast and Midwest ceramics maintained different traditions (Rookwood in Ohio continued glossy Art Pottery glazes, Lenox in New Jersey focused on translucent porcelain). The regional distinction matters because architectural pottery wasn't trying to compete with traditional ceramics categories. It created its own category.

The volcanic glaze technique that Cressey and others developed exists independently of Architectural Pottery - German manufacturers used similar approaches for what collectors call "fat lava" pottery (Scheurich, Bay Keramik, others producing 1960s-70s), Icelandic pottery (Glit) incorporated actual volcanic rock into glazes, Italian potters (Bitossi, Raymor) developed their own volcanic and textured surfaces. But the American architectural pottery companies positioned these glazes specifically within modernist interior design context rather than as standalone art objects.

Why These Surfaces Mattered

Walk into any well-preserved mid-century interior and you'll likely see: walnut furniture with minimal ornament, large windows, indoor plants in ceramic planters with matte or volcanic glazes, textiles in organic patterns. The aesthetic coherence comes from shared principles - material honesty, form following function, accessible luxury, connection between interior and landscape.

The glazes that defined architectural pottery embodied these principles through manufacturing decisions that were simultaneously aesthetic, economic, and philosophical. Volcanic surfaces celebrated clay as a material that could be both refined and raw. Matte bisque finishes let the form speak without glossy distraction. The production methods enabled middle-class access to design that integrated with modernist architecture.

The current collector market valuing these pieces at 100× their original prices reflects more than nostalgia. It's recognition that mid-century architectural pottery achieved what it set out to do - create classics that stood the test of time. The glazes remain visually distinctive 70+ years later because they solved real problems (production efficiency, indoor-outdoor use, aesthetic integration) rather than just following decorative trends.

For those researching ceramic techniques or considering their own pottery work, the mid-century approach offers useful lessons. Technical decisions (glaze chemistry, firing schedules, surface finishes) carry aesthetic and economic implications. What looks like purely artistic choice often reflects production realities. And sometimes the most lasting designs come from embracing what materials actually are rather than trying to make them pretend to be something else.