The key difference between primer sealer and undercoat is that a primer is applied on new surfaces and a sealer is used either as a substitute for primers or applied prior to a primer whereas an undercoat is used on surfaces that have been painted previously.
The terms primer, sealer and undercoat are used mainly during painting processes. A primer or an undercoat is chosen based on the nature of the surface that we are going to paint while the sealer is mainly used as a substitute.
CONTENTS
1. Overview and Key Difference
2. What is a Primer
3. What is a Sealer
4. What is an Undercoat
5. Side by Side Comparison – Primer Sealer vs Undercoat in Tabular Form
6. Summary
What is a Primer?
A primer is the first coat that is applied directly to a bare substrate. This name “primer” comes from the Latin word “prim”, meaning “first”. A primer that is applied prior to a paint can provide the surface with an excellent adhesion ability, and it can act as an anchor that aids a new paint system. Usually, good primers can seal, hide and bond, which can form a firm foundation for topcoats.
Typically, primers feature different binders as part of their ingredients, in order to provide the best adhesion. Moreover, the primer should contain binders that are compatible with the substrate. This substance can also inhibit moisture from reaching the substrate, which prevents subsequent coats of paint from sinking into the substrate surface. Further, a primer material can help to prevent stains from bleeding through topcoats and ruining the finished painting.
What is a Sealer?
A sealer is either a substitute for a primer or is applied prior to a primer. We can observe that some sealers function by sealing off surface porosity and providing the surface with good adhesion between the substrate and the new paint we are going to apply. These functions are similar to primers.
However, there is an important advantage of a sealer material over a primer – they can recondition old surfaces that are unfit for painting. Usually, the role of a sealer is to bind gypsum plaster. E.g. if we are interested in painting an over weathered concrete or crumbly surfaces, using a sealer as a base for the primer can protect the surface as well as bind the primer to the surface tightly. Also, we can apply a sealer as a barrier between incompatible finishing coats, e.g. when coating previous finishes.
What is an Undercoat?
An undercoat is applied over a sealer or primer for further strengthening functions of the primer and the sealer. These functions of primers and sealers include providing a barrier to prevent moisture penetration, improving the bond between topcoat and primer or sealer, etc. Moreover, the undercoat can improve the bond between topcoat and the primer or sealer, and provides a base for the topcoat.
As a general rule of painting, it is advised to use an undercoat if we are painting over an existing surface that has been painted previously and to use a primer if we are painting a new surface.
What is the Difference Between Primer Sealer and Undercoat?
The terms primer, sealer and undercoat are used in painting surfaces. The key difference between primer sealer and undercoat is that a primer is applied on new surfaces and a sealer is used either as a substitute for primers or applied prior to a primer whereas an undercoat is used on surfaces that have been painted previously.
Below info-graphic summarizes the differences between primer sealer and undercoat.
Summary – Primer Sealer vs Undercoat
When painting a surface, it is very important to choose the perfect primer, sealer and undercoat. The key difference between primer sealer and undercoat is that a primer is applied on new surfaces and a sealer is used either as a substitute for primers or applied prior to a primer whereas an undercoat is used on surfaces that have been painted previously.
Reference:
1. “Primer (Paint).” Wikipedia, Wikimedia Foundation, 23 Oct. 2020, Available here.
Image Courtesy:
1. “White primer bucket” By Daniel Case (CC BY-SA 3.0) via Commons Wikimedia
2. “3414649” (CC0) via Pixabay