Castle mortar was traditionally made from a mixture of slaked lime, sand, and a binding additive designed to improve its durability and workability.
Here's a more detailed breakdown:
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Slaked Lime: This is created by heating limestone and then hydrating it. The resulting lime putty provided the primary binding agent.
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Sand: Sand acted as a filler, reducing shrinkage and cracking as the mortar dried and cured. The type of sand could vary based on local availability.
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Additives (Binders): These were crucial for enhancing the mortar's performance. Common additives included:
- Animal Hair: Often ox hair, this improved tensile strength and helped prevent cracking.
- Clay: Added to increase plasticity and workability, making the mortar easier to apply.
- Ash (Volcanic Ash or similar): Provided pozzolanic properties, reacting with the lime to create a more durable and water-resistant mortar. This was particularly important in damp climates or for structures near water.
- Brick Dust: Similar to ash, brick dust could also contribute to the pozzolanic reaction and improve durability.
- Other organic materials: such as milk, urine, and vegetable matter.
- Water: Essential to hydrate the lime and create a workable paste.
The precise proportions of these ingredients varied depending on the specific requirements of the construction project and the local availability of materials. A skilled mason would adjust the mix to achieve the desired consistency, strength, and durability for the particular application within the castle's construction.
