The legendary durability and color of Salernes tommettes stem from the unique mineralogy of Var alluvial clay—rich in iron oxide (hematite)—processed in pug mills, hand-pressed into hexagonal pearwood molds, and fired in traditional wood-burning down-draft kilns where pinewood smoke creates natural variegated color flashing.
At a Glance: Key Takeaways
- High Hematite Mineralogy: Natural iron oxide (6% to 9% Fe2O3) generating intense crimson and terracotta hues.
- Pearwood Hexagonal Molds: Hand-planed wooden frames dusted with sand to facilitate tile release without deformation.
- Wood-Fired Down-Draft Kilns: Pine and oak timber fueling temperatures up to 1,000°C over 72 hours.
- Reduction Flame Flashing: Localized oxygen deprivation in the kiln producing smoky purple and dark amber variegations.
- Low Calcite Content: Absence of limestone pebbles prevents lime popping and structural pitting.
1. Mineralogical Composition of Salernes Alluvial Clay
The geological basin around Salernes in the Var region features unique deposits formed during the Cretaceous and Tertiary periods. The clay is predominantly an illite-kaolinite sedimentary earth with an exceptional concentration of hematite (iron oxide, \(\text{Fe}_2\text{O}_3\)), typically between 6.5% and 9.2% by weight.
Unlike clays from Northern France or England, Salernes clay contains virtually zero calcium carbonate nodules (limestone gravel). When limestone is fired, it converts to calcium oxide (quicklime); upon exposure to ambient air, quicklime expands dramatically as it hydrates into calcium hydroxide, causing catastrophic surface blowouts known as lime pops. The natural absence of calcite in Salernes earth allows tiles to maintain smooth, intact surfaces for centuries.
2. Pugging, Hand Molding & Pearwood Frames
Extracted raw clay is weathered outdoors through winter freeze-thaw cycles, then soaked in washing basins and passed through a mechanical pug mill to homogenize moisture and remove trapped air pockets. Tile-makers form each tommette using traditional wooden molds:
- Pearwood / Beech Molds: Dense, fine-grained hardwoods that resist warping when exposed to moist clay. The mold interior is beveled slightly outward (1° to 2° draft angle) to allow clean release.
- Sand Dusting (Sablage): The mold interior is dusted with fine quartz sand. A lump of clay (pâte) is thrown vigorously into the mold, compressed by hand, and trimmed flush using a taut brass wire (fil à couper).
- Air Drying (Le Séchage): The molded tiles are placed on slatted wooden drying racks in covered, ventilated barns (séchoirs) for 3 to 5 weeks to reduce moisture content from 22% down to less than 3% before kiln loading.
3. Thermal Dynamics of Wood-Fired Kiln Flashing
Traditional Salernes kilns are wood-fired brick structures utilizing Scots pine (Pinus sylvestris) and Holm oak (Quercus ilex). Pine wood burns with a long, luminous flame rich in volatile resins, creating superior thermal convection through the dense stacks of tiles.
The firing cycle lasts approximately 72 hours, reaching a peak temperature of 980°C to 1,020°C. During the final 12 hours, kiln masters deliberately alter the air dampers to induce alternating oxidation and reduction cycles:
Where reducing carbon monoxide gases strip oxygen from the hematite, the clay darkens into purple, brown, and charcoal flashings. Where oxygen is plentiful, brilliant iron reds and warm oranges predominate. This controlled pyrotechnic chaos gives each antique floor its unrepeatable, vibrant warmth.
Salernes Firing Cycle Parameters
Use this reference table to calculate exact physical dimensions, ratios, and specifications before purchasing:
| Firing Phase | Temperature Range | Duration | Atmospheric Condition & Physical Action |
|---|---|---|---|
| Smoking / Water Smoking (Petit Feu) | 20°C to 200°C | 24 hours | Slow expulsion of hygroscopic and chemically combined water; low heat |
| Vitrification / Full Fire (Grand Feu) | 600°C to 980°C | 36 hours | Breakdown of clay minerals, silica sintering, hematite oxidation |
| Reduction Flashing (Braisière) | 980°C to 1,020°C | 6 to 8 hours | Restricted oxygen dampers; wood smoke creates surface color variation |
| Natural Cooling (Refroidissement) | 1,000°C down to 50°C | 48 hours | Sealed kiln doors; slow annealing to prevent thermal shock shattering |
Material & Manufacturing Constraints
Every successful decoration project must account for physical and environmental constraints:
Dimensional Variance
Hand-molded tiles shrink 8% to 12% during drying and firing; expect ±2mm variance in width and thickness across batches.
Color Batch Matching
Never install tiles directly from a single crate; blend tiles from multiple crates across the floor to ensure even color dispersion.
Crafting Traditional Hexagonal Tommettes
Execute this professional sequence to achieve flawless results without backtracking:
Clay Digging & Winter Weathering
Excavate alluvial iron clay in autumn; leave in outdoor mounds over winter to break down lumps via natural freeze-thaw cycles.
Pugging & De-Airing
Mix raw clay with pure water in a pug mill to achieve uniform plasticity (18-20% moisture) without trapped air bubbles.
Sand Dusting & Mold Throwing
Dust the hexagonal pearwood mold with fine silica sand; forcefully throw clay into the mold to fill all six corners.
Wire Trimming & Board Ejection
Draw a brass wire across the mold frame to slice off excess clay; invert onto a drying bat to release the raw tile.
Slow Barn Drying
Stack tiles on slatted wooden drying racks in shaded sheds for 4 weeks until moisture drops below 3%.
Wood-Fired Kiln Stacking & Firing
Stack tiles vertically on edge in herringbone patterns inside the kiln; fire with pine logs to 1,000°C over 3 days.
Common Mistakes & Countermeasures
Avoid these costly errors that compromise aesthetics, ergonomics, and budget:
Rushing the drying phase before kiln loading
Using industrial gas firing without reduction cycles
Project Execution Checklist
Track your physical progress. Checkboxes persist automatically on this device:
Frequently Asked Questions
Why are Salernes tommettes traditionally hexagonal rather than square?
In addition to eliminating continuous weak grout lines, the hexagonal shape maximized the efficiency of wood-kiln space. Hexagonal tiles can be stacked tightly in interlocking honeycomb formations with uniform airflow gaps between tile edges, optimizing fuel consumption in wood-fired kilns.
How can you tell an authentic antique Salernes tommette from a reproduction?
Authentic antique tommettes feature subtle irregularities: slight variations in thickness (15mm to 22mm), delicate wire-cut marks on the underside, occasional wood-ash inclusions, and deep natural color flashings, whereas modern machine-made replicas are perfectly flat and uniform.
