Comparing an Open Cell and Closed Cell Backer Rod

In a quick overview, backing rods have three primary functions. First, it controls and dictates the size of the joint to be bonded. Second, it controls the depth of the bead. Third, it gives a solid surface to base the caulking material or tooling operations.

Among these functions, it’s very crucial that the sealant to be used is securely pushed between the backing and the tool in order for it to move sideways. It is for this reason that the tooling should be done securely on a firm backer rod. This backing material comes in two options: closed cell and open cell. In order to choose the correct one for your application, we are comparing these two types of backing rods for you to consider.

The closed cell backer rod

The biggest benefit of this type of backer rod is its rigid structure because it is close. However, it is also prone to several problems like out-gassing that may happen during its installation when the material gets punctured. You can picture it out like an inflated balloon where air is forced out of the rod, bubbling into a sealant. This phenomenon causes a blister look on the tooled sealant.

Another possible issue is the loss of compression to the joint walls of the rod, causing moisture to get inside the backing material. However, when installed properly and with enough preparation, the closed cell rod can last for a very long time.

The open cell backer rod

Unlike its closed-cell counterpart, an open-cell rod is perfect for applications where out-gassing becomes a great concern such as the case in regions where climate changes are huge problems. However, the biggest concern in using this type of backing rod is its inability to be used in exterior applications where water and moisture can cause damage to the supported structure or sealed joints.

The good news is that in decades of our experience, Alcot Plastics has never experienced serious problems using any of these rods. Thanks to the quality of the products we manufacture to ensure that each application becomes a success, not a headache.