Construction Design-Caulking 101-Terminology

Before having a conversation with someone about a specific topic, you really should know the subject matter, the definitions and terminology related to the topics being discussed.  Talking about sealants and caulking is no different.  In the coming blogs, we will be chatting about many different topics with regards to sealants, this thing we are calling caulking 101.  This blog post is the prerequisite for those conversations.

Caulks, sealants, adhesives-what are the differences?

Caulk is a type of sealant that has less movement or flexibility to other sealants.  It’s often used as a cosmetic solution instead of a true “keep things out of a joint” product.  To caulk or caulking can also be used as a verb, the application of a sealant.

Sealant is a substance used to bridge a gap between two or more surfaces.  A sealant needs to both look good and perform, keeping unwanted “things” from entering the joint.  Sealant are designed to move but remain stuck with the surfaces.  Caulking and sealant are often interchangable terms, my favorite word used to discribe sealants is “Pookie”.

Adhesives tend to have high bond strengths, usually with less flexibility.  Adhesives are used to hold two or more surfaces together, a chemical bond if you will.

Hybrid Sealant or hybrid adhesive is a product that acts as both a sealant and adhesive, combining the two worlds, but usually not the best of either.  Hybrids have good flexibility, but not as good as a true sealant and good adhesion, but not as good as a true adhesive. 

Common application terms.

Bead is the sealant as it is applied from the tube to the substrate.  Different beads can be created by the way the nozzle is cut or by changing the angle of the caulking gun to the substrate.  A ribbon bead is a thinner, flat bead and a round bead is a larger amount of sealant.

Substrate is the surface or surfaces to which the sealant is bonded.  These can be wood, metal, glass, or many other surfaces common in the construction industry.  There aren’t many surfaces where a sealant cannot be used.

Joint is the space between two substrates that require a sealant.

Cure-The hardening of a sealant into its finished condition.  Different sealants cure differently than others.  Acrylic/water based and solvent based sealants both cure by evaporation whereas polyurethane and silyl-terminated polyesther (STPE) sealants require moisture to cure.  Some sealants can take days to fully cure while others are dry to the touch in less than an hour.

Tooling is to manipulate a sealant into a specific shape.  If you’ve ever tried to run a bead of any type of sealant, you know it’s hard to make a joint look good right out of the tube, using a wet finger or some other tool to smooth the joint is often necessary.

Bond Breaker is a product used to prevent a sealant from bonding to a surface.  Backer rod and a bond breaking tape are specific products used as a bond breaker.

Performance terms.

Adhesion is the “stick to others” part of a sealant.  Adhesion is an attraction between two different materials.  A related term is Adhesion Failure which is the loss of connection between the sealant and substrate.

Cohesion is the “stick to itself”, it’s the force of attraction between the same molecules.  Cohesion Failure is when the sealant loses bond with itself but the bond to the substrate remains.

Elasticity/Elongation is the stretch and return to normal of a material.  My favorite analogy is yoga paints, they stretch to fit but return to their original size when taken off.

Tensile Strength with regards to sealants is the stress a sealant can withstand while being stretched without failing.  An important consideration for joint movement.

This is not an all-inclusive list of sealant terminology, but it’s a good start for caulking 101.  The next topic is sealant chemistry.  Water based, solvent based, polyurethane, silicone and others will all be discussed.  We will also have a quick interview with Nathan Ferraro, also known as Sashco Nate on why Sashco only produces water and solvent based products.  Stay tuned.

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