You may have two cans of paint in your house and one is labeled for outdoor use and the other is labeled for indoor use. It is possible that you think that if both have the same pigment and the same brightness ... and it is that both are also used to paint surfaces. But if you use an exterior interior or interior exterior paint, the results may not be what you expected.
The chemistry found in paint components today has changed from a few years back now. Manufacturers and professionals alike recommend using paint cans according to how they are labeled: interior paint for interior areas and exterior paint for exterior areas.
When you choose the paint
When you are going to choose the paint there are two basic aspects that you have to know: there is the water-based paint and the oil-based paint. Latex paints, acrylic paints are water-based, while alkyd paints are oil-based. Both paints are for interiors. There are different types of outdoor paints.
When it comes to exterior paint, oil-based paints are better because they resist dirt. Although water-based latex paint is commonly used for exterior areas because it has to last longer than oil. This type of paint when used in outdoor areas better withstands humidity, external factors, temperature changes, and also takes much less time to dry.
The paints that are used for the exterior contain additives that give them great longevity in the exterior areas, better resists cracking and also society. In addition, outdoor paints are designed in such a way that it can better withstand the damage that UVA rays can cause.
Water-based paints are suitable for interiors. Rather than having additives to withstand dirt better, the chemistry of interior paints are meant to be tough and sticky. They are also designed to withstand the typical dirtiness of any indoor area (splashes, rubbing, etc.).
Differences between exterior and interior paint components
The lack of some additives provides some disadvantage to interior paints when used on external surfaces. The difference between paints formulated indoors and outdoors doesn't end here. The differences also appear when looking at some components of the paint: pigments, binders and liquids.
Pigment
Pigment is what provides paint with color. Interior paints may contain organic color pigments but may fade if used outdoors. Exterior paint formulas avoid these pigments to increase the resistance of outdoor paint.
Binders
The paints are created with additives known as binders, which are used to bind the pigment and at the same time provide surface adhesion where it is to be painted. Exterior paints have to be more resistant to withstand the adverse effects of the environment. In this way the paint becomes resistant to cracks and better controls humidity.
Liquids
Interior and exterior paints also differ in the types of liquids that are used to create one type of paint and the other. Interior paints, specifically water-based interior paints, including latex, are designed to contain the lowest levels of volatile organic compounds (VOCs). VOCs are used as solvents in the liquid component of paint and vaporize at room temperature. VOCs are linked to both short-term and long-term health problems, from headaches and dizziness (short-term) to respiratory illnesses and liver damage (long-term).
They can also be associated with certain cancers. You need to find paints that have VOCs with very low or no levels.
So can I use the interior paint for exterior areas?
Once you have reached this point, you will have been able to verify that it is better that if you are going to paint an interior area you use a paint that is intended for it. The same happens if you are going to paint an outdoor area, which then it is better that you buy and use a paint that is intended exclusively for painting exterior areas. You can find the most recommended exterior paints this link.
If you have doubts about which paint may be best for a specific area of your home, then you will only have to ask a painting professional so they can guide you. If you are going to paint your house both outside and inside, you should have two different types of paint cans, one that is intended for interior painting and another that is intended for exterior painting. Once you know this, you will only have to choose the color that you like the most and buy the right tools!