Guédelon Castle 2023: Celebrating 13th-Century Medieval Crafts

In the third installment about building a castle complex, we present what has been learned about craftsmanship in the Middle Ages.

Guédelon Castle complex in 2023. Copyright Guédelon

While staying true to the building methods used in the 13th century, the construction of Guédelon has been ongoing for 26 years. CEO Maryline Martin, working with head stone mason Florian Renucci, has led the effort to complete the project. With an estimated 10 more years to completion, much has been accomplished to date regarding how much has been learned about medieval construction methods.

Guédelon is situated on property bought for the purpose of building a 13th-century castle from scratch. Everything necessary for the construction of a castle is there: a quarry for stone, a forest for wood, sand, water, and clay. Many crafts were also needed to build Guédelon, including those for the finishing touches that make a castle a home.

The Blacksmith and Stone Masons

The construction began with the skills of a blacksmith. Blacksmiths in the 13th century made steel by heating iron over a charcoal fire for a long period of time. The modern-day term would be smelting. The Guédelon team makes their own charcoal to fire the furnace to make the steel; the steel can be made into anything needed for all the craftworks, from nails, to knives, to tools.

Blacksmiths removing the iron bloom (oxides) and beginning to hammer out impurities. Copyright Guédelon

The ferruginous stone from the Guédelon quarry was critical for making the tools, as it had a high concentration of iron to make their “mild steel,” a metal made from iron and carbon that comes from the ferruginous stone. Stone masons helped make the furnace that could withstand a temperature up to 3,000 degrees Fahrenheit, enough to create the mild steel from the iron ore. 

Nothing is wasted at Guédelon, as worn tools and steel scraps are re-melted, too. Everything comes from the land and is reused. This is a major example of what can be learned from Guédelon about the use and reuse of our own products and resources.

Touring the grounds this spring, I watched as stone masons hewed large pieces of ferruginous stone to continue to build the towers of the castle. The stone masons were trained in the craft of stone hewing, using only tools made by the Guédelon blacksmith, just as they were made in the 13th century.

A stone mason hews stone with handmade tools. Goggles are required by the French government for safety. Copyright Guédelon

Limestone is used to set stones and for limewash for the walls. It takes 72 hours in a kiln to create the lime ash to produce the limestone mortar and limewash. Limestone has a number of valuable properties: It is flexible, durable, and uses little energy to produce, making it eco-friendly, something that is valued in modern-day construction. Stone block construction laid the groundwork for the building.

Carpenters and Woodworkers

In the 13th century, pigeons were raised for use as both messengers and for food. Carpenters first built a framework for the pigeon-loft, then placed split oak shakes on the roof. Beneath the pigeon loft is a wall constructed from small, broken pieces of ferruginous stone, carefully arranged. Along with stone hewing, the stone mason’s arrangement of the rubble is an art in itself, as if putting together a puzzle.

Carpenters raise the first trusses for the pigeon-loft, which are placed on a crenelated parapet. (Copyright Guédelon)

For the tower’s construction, oak  is used as it is durable and plentiful in the Guédelon forest. The woodworkers use the tools that the blacksmith has created to craft and produce 9,000 shakes (shingles) by hand, just as it was done 1,000 years ago. The carpenters will place the oak shakes on the pigeon-loft frame once its construction is completed. One can call this the earliest assembly line process.

Protruding from the sides of the tower are the ends of several putlogs, long pieces of wood. Putlogs, or any type of strong material, pierces the walls in order to support scaffolding or hold up layer after layer of the stone walls during construction. When the putlogs are removed, the remaining holes are patched with mortar.

Guédelon carpenters are so well trained in 13th-century construction that they have been called upon to train those working on the reconstruction of the Cathedral of Notre Dame in Paris. Besides helping to recreate the spire, they have provided instructions on the hewing of lumber for the beams and joining. This training is no longer offered in the high-level carpentry-joinery courses. All of what they have been able to teach came from their own training and discoveries at Guédelon. The carpenters’ training has also been valuable to the architect at Notre Dame to accurately estimate of the amount of lumber needed and the costs for construction.

Fabric Dyers and Painters

The painter and her team make the dyes used to paint the designs on the chapel walls and linen window coverings. She first experimented with different minerals to get the colors needed: Yellow and red ochre pigments come from iron; other colors are made from charcoal, lime putty, hematite, burnt clay, and burnt charcoal dust. The project team has been able to create 15 colors using materials found on-site.

A model of a window for Guédelon’s chapel, made by a carpenter, is carried to its setting. Copyright Guédelon

Installing painted linen windows into the tracery stone framework. Tracery is a decorative method of providing the stone framework to place wooden frames in, and the support needed for the chapel windows in the Guédelon chapel. Copyright Guédelon

Although glass was available in the 13th century, it would have been too expensive for a modest castle. At Guédelon, after stone masons create the holes in the castle walls for windows, carpenters make window frames and frames for linen, which is stretched over a frame for window coverings. Parchment made from goat skin had been tested for the castle windows and was found to split during hot weather. Linen was then chosen for its lasting quality. Typical of the 13th century, tradesmen gathered at markets to exchange their goods, and these markets are where linen could have been acquired.

Once the linen is placed on a frame, the painter creates the patterns on the linen with mineral dyes. Beeswax from Guédelon’s hives is then used to coat the window coverings. The windows are translucent, not transparent, allowing in light, but not a clear view in or out.

Painters create the linen used for the castle windows.  The first windows to be completed were for the chapel inside the castle; they’re in a traditional pattern like the stained glass we see today. Some of the chapel windows will have a wood tracery, made by the carpenters to place over the painted linen, creating a stained-glass type of pattern.

Tile Makers, Potters, and Bowl Turners

Tile making was seasonal during the medieval period. Clay would be dug up in the winter to allow it to “weather” until spring or summer when conditions were drier, then the tiles would be fired. The temperature of the kiln creates the tile color as does different clay colors, which they are experimenting with today. Clay for the pottery and tiles comes from the property’s forests.

Floor tiles will be installed throughout the castle in places used by the castle’s lord and family, such as the chapel. Slate flooring will most likely be used for the guard’s quarters.

The potters built five different kilns to fire clay roof tiles and vessels, experimenting until they found one that worked. This is another discovery that contributes to the knowledge of 13th-century construction.

A counter-relief tile after a pattern has been pressed into clay, a technique that began in the 11th century. Copyright Guédelon

The tile maker creates the designs used to stamp the tiles. The clay is rolled into a mold and then stamped with the design in a raised pattern creating a counter-relief tile. After stamping the tiles, and firing them, a glaze is applied. Craftsmen will re-fire the tiles in the kiln after glazing. The artisans have come up with new lead-free mineral glazes, made from borax and fern ash, to be used on wooden bowls for eating and on pottery for food storage or serving. The potter is now working with the tile maker on a new curved roof tile for the communal bread oven.

The bowl maker turns bowls on a handmade pole lathe made by the blacksmith and carpenters. The ingenious hand-powered system allows the bowl maker to turn bowls for food as well as for dye pigment.

A bowl turner carves out wood for bowls on a handmade pole lathe. Copyright Guédelon

The multilingual crew at Guédelon allows all visitors a chance to ask questions of a craftworker who shares their language. And guided tours are available in English, German, and Dutch.

Guédelon is experimental archeology on a massive scale. The research done for Guédelon has provided information to archeologists, architects, and historians about how the construction was done and has allowed for training the craftworkers in the methods used. It is not a recreation of life in the 13th century, but a treasure trove of information on the techniques used to build a castle.

Ms. Martin explained the value of the manual trades: “Now Guédelon has become a training center for heritage skills, and we now recruit talented young people who have chosen manual trades as their career.”

You can visit Guédelon from Paris on the Guédelon bus. Visit Guédelon.com for more information.

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