Terms and definitions
Pin: Reinforcing an adhesive repair by drilling the fragments and inserting rods or pins to help strengthen the connection and contain shear forces.
Repin: Reuse or replace loose rods that were originally used to stabilize a marker.
Reset: Excavate the area where the stone is to be reset about a foot down and fill with the sand/peastone mixture up to the level where the stone should be sitting. Remember to tamp often and use water to help only enough to keep the proper mixture for tamping the soil down.
Poultice: Substance applied to the stone and left for a time to help remove the built up growth such as moss or lichen on the stone.
Drilling Holes: The number needed will vary with the project. As a rule they are drilled in a staggered pattern, keeping them spaces so as to avoid splitting the stone. The diameter should be about 1/8" greater than the diameter of the pin. The depth of the hole you drill should be about half the length of the pin. Choose the pin size according to the job. A small pin, would be approximately 1/8" to 1/4" in diameter by 1" to 2" long.
Pins: Non-corrosive pins should be used. Thermoplastic rods, such as nylon, have coefficients of expansion similar to epoxy and are an excellent choice.
Threaded or grooved pins will provide a good surface for adhesion.
Adhesive: Two epoxies are used in this type of repair. The adhesive used to hold the pins should be a high-strength (high modulus) epoxy used for structural repairs and setting of bolts. A more flexible adhesive epoxy, a low modulus compound, should be used to bind two fragments together.
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