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The Spanish padres were not trained as engineers or architects or carpenters. They had no certain sources of a supply of building materials from beyond the California coast. They had to find materials around them to use in building. The building material most readily available to them was the soil under their feet.

The California soil used to make adobe bricks and tiles was a clay type of soil that hardened when heated or dried. This made it possible to construct permanent buildings with bricks that were made mostly of dirt. Making adobe bricks was one of the first crafts that the Native Californians learned at the mission.

Hundreds of adobe bricks were needed to construct each mission building. Many people worked at the task. The first step was to prepare the clay mixture. If the soil was dry, it had to be pounded to a smooth powder. The soil was combined with dry manure, straw, and water in a wide, shallow pit in the ground. The mission workers used their bare feet to mix the clay, tramping around in the pit until the mixture was the right consistency for pouring into the molds.

The molds for making adobe bricks were wooden frames (like boxes with no bottoms). One worker shoveled in the wet clay mixture, while another patted it into the corners of the mold and smoothed the top. Then the mold was lifted carefully from the newly-formed brick, and was filled with more adobe clay to make another brick. The molds were washed often to keep the adobe mixture from sticking.

Filling and removing the mold was a task that required special skill. The men who could do this task well were respected by the other workers. One report states that nine men could make 360 adobe bricks in a day.

After the adobe bricks were molded, they were left in the sun for several days to begin drying. When they were partially dry, they were turned up on one edge, so they would dry more completely. The workers placed the bricks in rows, in a zigzag pattern that kept the bricks from toppling over while they were drying. If the weather was dry, the bricks would be ready to use in about ten days. It took almost a full year, however, for the adobe bricks to become completely dry. This meant that they were used in building long before they were totally dry.

The use of sun-dried adobe bricks to construct the mission buildings made it necessary to make the walls of the buildings low. The bricks were too heavy to stack them up very high. Also, the walls had to be made very thick to hold the weight of the bricks. Since these adobe bricks would dissolve if they got wet, the roofs of the buildings had to extend out over the walls, to keep the rain from hitting the bricks.

The size and quality of the adobe bricks differed from mission to mission, depending on the type of soil available. The most common size was about 12 inches wide, 20 to 22 inches long, and 4 inches thick. The bricks each weighed about 60 pounds. Sometimes specially-shaped bricks were formed to be used at the edges of doors and windows.

When these adobe bricks were ready to be used to make a building, they were cemented together with more sticky adobe mud, or with lime mortar. The workers used handmade wooden trowels to spread the sticky mud or lime mortar between the bricks.

Lime mortar was made from limestone and seashells, heated in a very hot kiln (brick oven) until they became soft. When water was added to the softened seashells and limestone, the mixture could be used to hold the adobe bricks together. A similar mixture of limestone, water, and sand was sometimes used as a plaster to spread over the adobe walls. The limestone plaster helped to protect the adobe bricks from the rain.

The roofs of the earliest mission buildings were made of thatch (dried reeds). These roofs caught fire very easily. When the padres began to use tiles for the roofing material, the mission buildings were much safer. This use of tile roofs was an important development, not only to enable the missions to prosper, but also because it set a trend in California architecture. Similar tiles had been used for roofs in Spain.

Roofing tiles, called tejas, were made from the same materials as the adobe bricks. A flat rectangle of clay was formed. It was then carefully placed over the round piece of a log which had been sanded so the clay wouldn’t stick to the wood. Some stories tell that the roof tiles were molded over the legs of the Indian workers, but other sources say that is just a legend.

After the clay was molded into the curved shape, it was dried in the sun for several days. Then the tile was baked in a kiln for many days. The baking at a high temperature caused the adobe clay to turn red.

Mission San Luis Obispo has been credited with the development of roofing tiles. Father Serra’s diaries, however, say that the first roofing tiles were made at Mission San Antonio de Padua. Mission San Luis Obispo then perfected the process. They made the tiles in large quantities and supplied them to other nearby missions. At San Luis Obispo, horses were kept walking in circles to mix the adobe clay with their hooves.

Some mission buildings had tiles on the floor. These floor tiles, called ladrillos, were made from a thicker mixture of adobe clay, straw, and water. They were molded in much the same manner as the adobe bricks, partially dried in the sun, and then baked in kilns to make them hard.

Adobe tiles were also used as water pipes at many missions, to carry the water from a river or stream to the mission compound, or to the fields for irrigation.

Pottery bowls and pots were made at the missions, though not in great quantities. Clay pots were not commonly made by the California Indians, who instead made excellent baskets which served their needs for storing food. However, in later years some missions had pottery wheels for making bowls.

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