First and foremost, the best way to make your interior paint cover all surfaces is to buy a sufficient amount of paint. You should buy about 20% more paint than you estimate you will need. That will account for spills, drops, or simple miscalculations. Furthermore, you should buy it all at the same place and at the same time. That means that even if the hue is slightly off, it will all be the same hue. If you buy some more later that is supposed to be the same hue, it could be slightly different due to heat, humidity, or human error. With all of that being said, you’re not perfect and might find that you didn’t buy enough paint. Alternately, you might have some paint left over from a previous job and not want to buy more. Here’s how you can stretch it.
1 – Water It Down
Some interior latex paint is marked as safe to mix with water. Sometimes, the paint is intentionally mixed slightly thicker than it needs to be. That will make each coat cover blemishes and primer more completely. So, if you do water down the paint, you should be aware that it will have less coverage. You’ll have a more difficult time covering up primer, old paint, old wallpaper, or blemishes.
If you choose to do this, it’s important to sand down any surface until it’s as smooth as possible. Also, remove wallpaper and choose a primer that better matches your final paint color.
2 – Thin It With Paint Thinner
Paint thinner is also an option; you might see it listed as mineral spirits. When the product is labeled “mineral spirits” it is in a highly refined state. When it is listed as “paint thinner” it is not quite as refined. Paint thinner typically suffices for most applications. You should look on the can of paint you have to see if there are instructions for how to mix the paint with paint thinner. Some will have instructions. If not, you should do a quick internet search to find the specific proportions.
Be sure to use measuring cups to measure out specific amounts of paint thinner. Also, be sure to not use those measuring cups for food again; mineral spirits can be very caustic.
3 – Mix With Other Paint
Finally, if you have other paint, you can mix the different shades of paint together as long as they’re all the same kind of paint. The color might not be a desirable color, but if all you need is coverage, it will work.