How interior paints are different from exterior paints?

How interior paints are different from exterior paints?

Interior and exterior paints are different in their composition because these serve different purposes. Although the color shades might be identical, the paint properties of interior paints are quite different from that of exterior paints.  Since exterior paints must withstand the elements of weather, prevent mildew growth, and the color must not fade for a long time, its composition is different from interior paints that should resist staining and facilitate quick cleaning.  How exterior paints are different from interior paints, you can see it here.

Paint chemistry – The basics

Resins, solvents, additives, and pigments are the common ingredients for all paints. The solvent is responsible for making paints ‘wet’, and the solvent dries after some time while allowing the paint to adhere to the surface. The paint that sticks to the surface contains the other ingredients.  The pigment imparts color to the paint. The resin acts like a binder and ensures the adhesion of the paint to the surface, while additives impart different properties to the paint, like mildew resistance. Acrylic or Epoxy and silicone resins are ideal for paints.

The solvents and pigments in both interior and exterior paints share similar properties. Oil-based or water-based paints are suitable for outdoor. Oil-based paints do not suit interior paints because they contain volatile organic compounds (VOC) that mix with the air, vitiate the indoor environment, and pose health hazards.  Moreover, oil-based paints have an obnoxious odor and are difficult to clean.

 Resin makes the difference

The most glaring difference between exterior and interior paints is the resin content.  Resin is the binding material in paints that ensures the proper adhesion of paints to any surface. The quality of resin impacts how well and how long the paint sticks to the surface. 

Exterior paints must withstand harsh weather elements, including sunlight, wind, rain, and snow, and should have suitable properties to resist moisture and temperature fluctuations. The paint should not peel off easily and even resist chipping and fading. To meet the requirements, the resin used in exterior paints must be softer. 

Moisture and huge temperature fluctuations are absent inside homes, and these are not an issue for interior paints. Therefore, paint manufacturers use more rigid resins in interior paints as it helps to cut down on scuffing and smearing. 

Characteristics of exterior paints

Exterior paint protects the building from moisture due to rain and snow, the harmful UV rays of sunlight, and fungal growth. The paints can prevent mildew and color fading even in the face of high temperatures. Exterior paints must maintain their gloss and shine for many years. Since the paint uses softer resin, it prevents cracks from developing quickly due to expansion and contraction when the temperature fluctuates. Exterior paint needs sunlight for curing and is not at all usable for painting interiors. 

Characteristics of interior paints

Interior paints are more for aesthetics and decoration, although it creates a protective layer on the walls to prevent dampness while ensuring easy washability for maintenance.   Interior paint can withstand abrasion, resist staining, and does not damage when scrubbed. However, it is delicate than exterior paint.  

Interior paints being washable are easy to clean. It has very low VOC hence safe for indoor use.  

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About the Author: Barry Lachey

Barry Lachey is a Professional Editor at Zobuz. Previously He has also worked for Moxly Sports and Network Resources "Joe Joe." he is a graduate of the Kings College at the University of Thames Valley London. You can reach Barry via email or by phone.