Brick Types, Manufacturing, and Mortar Guide
Brick Types, Manufacturing, and Mortar
Brick Classification by Texture
- Rough or Coarse Bricks: These bricks are made from unrefined earth, molded by hand, and fired in simple outdoor furnaces called anthills (piles of bricks covered with burning firewood).
Firing Degrees and Brick Quality
The firing degree determines the brick’s quality:
- Escafilado: Holy brick
- Recocho: Over-fired brick (best quality, deep red color, most used in construction)
- Good Looking: Well-fired brick
- Brown Porter: Under-fired brick
- Fine Bricks: Made from well-prepared clay, shaped by table or press, also called brick press table bricks.
In Madrid, bricks are made on land near the Henares, Jarama, and Manzanares rivers. These bricks have a perfect shape, uniform firing, and excellent quality, making them suitable for exposed structures, such as the Customs House (Ministry of Finance) on Calle de Alcala.
Brick Classification by Shape
- Rectangular: The most common shape, a rectangular prism.
- Molded: Similar to rectangular bricks but with varied shapes for specific placements, molded by hand or mechanically with precise dimensions (e.g., wedge-shaped, keystone-shaped).
- Gaps (Hollow Bricks): Rectangular parallelepipeds with holes, offering greater strength for equal mass, lighter weight, more homogeneous firing, and better insulation against cold, heat, and moisture.
- Rasilla: Smaller than ordinary bricks, often hollow, mechanically manufactured for perfect shape, with stripes for mortar attachment, used to build vaults.
Brick Manufacturing Process
The manufacturing process can be manual or mechanical and involves the following phases:
- Excavation: Clay is extracted in autumn and transported to the manufacturing site. The land is cleared of boulders and foreign materials using shale. The land is left exposed over winter to allow air, humidity, and frost to decompose organic matter, a process called “land rot.” This prepares the land for correction and kneading.
- Correction of Land and Kneading: Correction involves adding other clays to improve quality (not always performed). Kneading involves mixing the clay with water until softened, then kneading with shovels, hoes, or bare feet until a consistent dough is achieved, ready for molding.
- Molding: Done with a rack and arch wire. For hollow bricks, wood strips are used to create the holes.
- Drying: The molded bricks are placed on the ground (Rejala) or on horizontal and vertical columns to air dry.
- Firing: The dried bricks are baked in an oven.
Mortar (Attachment Material)
Mortar is a mixture of sand, water, and a binder (cement, gypsum, or lime). It is fluid during application, then solidifies and adheres to the primary materials.
Types of Mortar
- Lime Mortar: Made of lime, sand, and water.
- Cement: A mixture of clay and calcareous materials cooked and finely ground, which solidifies and hardens when mixed with water.
- Concrete: A mixture of small stones, sand, and cement mortar.