Caulking: Encyclopedia - Caulking

Caulking

Caulking is a process used to seal the seams in wooden boats, in order to make them watertight, or to close up crevices in buildings against water, air, dust or insects.

Caulking - Marine Use

A traditional method of caulking used oakum, which consists of pieces of untwisted rope soaked in tar. The same effect may be achieved by using a caulking mallet and a chisel-like device called a caulking iron to put double-wound cotton strands into the gaps.

An old term for caulk in a maritime context is paye, and the longest joint on a ship was referred to as “the devil”. It was common for sailors to have to re-caulk this joint as a punishment. This practice gave rise to the terms “time to pay(e) the devil” and “stuck between the devil and the deep blue sea”.

Caulking - Building Construction

Caulk (calk) can refer either to the caulking substance or to the process of applying it. Caulking as a term has spread to the building trade, meaning the activity of closing up joints and gaps in buildings.

This is mostly done with ready-mixed construction chemicals sold as caulk such as silicone, polyurethane, polysulfide, sylil-terminated-polyether or polyurethane and acrylic sealant. Unlike construction caulk, which is applied where no building movement is expected, a sealant is made of elastomeric materials that typically allow movement of 25% to 50% of the width of the joint. Silicone sealants form a durable, water-tight seal, but are not paintable. Other sealants are paintable.

One-component sealants are commonly sold in cartridges which are loaded into a pistol-like caulking gun (opening at the side) or barrel gun (opening at the end) for application. During the tool-working time that varies by chemistry, the bead can be pressed into the joint so that it can bond with the materials on both sides and smoothed. The time it takes for a chemical sealant to harden is known as cure time and varies by temperature and humidity. Issues of technique that may not be obvious to first-time users:

• The nozzle must be chopped short to match the intended size of the bead. If the opening in the nozzle is too small, the bead is liable to bunch and is difficult to keep even.
• Common tools are a pointing tool, shaped wood, wet finger or a spoon. Detergent should not be added to the moisture for tooling since it may drip onto the bond surface causing a loss of adhesion.
• For neat work, the worker may apply painter's masking tape beforehand, taping off the areas on each side of the joint to catch any surplus and removing the tape again before the tooling time has expired.
• To prevent three-sided adhesion or to avoid sag in wide, deep joints, a backer rod made of plastic foam can be pressed into the gap before caulking.

Backer rod can also be used to fill cracks in sidewalks, and other masonry before caulking. It is comprised of a foam roll that is generally about 1/4 inch to 1 1/2 inch thick. The material is stuffed into the cracks to be sealed and then caulked over.

Adapted from the Wikipedia article "Caulking", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki