The bottom line is that watery paint is unusable. So if your paint is too watery and you attempt to use it to paint your home, you will notice that the paint won't adhere to surface correctly. It will be 'thin' and therefore will perform poorer than expected.
Please don't add water. It is just thinning out your paint and making it less durable. You should not have to touch up everytime you touch your walls. This is just making your paint worse. Source, I work at a paint store.
You might notice the consistency of your paint has changed. There may be a “skin” on the surface or lumps that won't stir out. If either of these is present, your paint has most likely expired.
When you thin too far, the solvent side of the ratio goes way high and you lose both control of the paint (it runs everywhere when you put it down instead of laying where you place it) as well as pigment coverage (more solvent means less of the ratio is pigment.)
When a painting contractor waters down paint, they are typically adding a significant amount of water to it. Think two gallons of water for every five gallons of paint. In contrast, the process of thinning paint involves a relatively small amount of water: 2-4 cups for every five gallons of paint.
You want it thick enough to ensure adequate coverage but not so thick that it leaves smears and ridges. Likewise, you don't want it so thin that it doesn't cover your primer or leave drip marks. Using quality paint rollers and brushes helps to achieve a consistent layer for a flawless finish.
Aside from consistency or texture, another way to know if the paint's gone bad is just to smell it! If it smells unpleasant or you see mold, you will need to discard it (correctly). And, yes, mold can grow inside a paint can and be a serious health hazard if you put it up on your walls.
What happens if you use expired paint? If the paint has a bad smell, you'll be adding that odor to your walls. In addition, expired paint will not provide even color coverage, the finish may not be smooth, and the paint is more likely to crack or chip.
Blistering and bubbling paint failure
Blistering is the appearance of bubbles on the painted surface. They are usually caused by moisture which can come from several sources.
Behr's color Watery HDC-CT-26 perfectly captures that mellow, somehow warming shade of blue that's as soothing as a set of flannel sheets on a crisp night.
A too-watered-down mist coat, however, will evaporate before soaking into plaster and won't provide a bond.
Discolored – This type of damage is the most easily recognizable. Water has discolored the paint and is soaked into the surface. The paint will be discolored in a ring around the affected area. Do not simply paint over this area as the painted area and the surface beneath still have water that will damage future paint.
Why it happens: An excessive amount of paint on your roller or paintbrush can cause paint to drip and run. Streaks, where paint is unevenly distributed on a wall, typically result from having too little paint on your roller or brush. What you'll need to fix paint drips, runs and streaks: Paintbrush.
How much water? You should add max 10% of water of the total volume of the paint.
Impacts on Texture and Finish
If the paint is too thick straight out of the can, it may need to be thinned using the appropriate thinner (water for latex paint, mineral spirits for oil-based paint, etc.) to reach the right consistency.
For unopened paints that are oil-based or alkyd-based, the shelf life could be up to 15 years. Additionally, chalk paint has a shorter lifespan from 1-3 years, and milk paint only lasts 1-2 weeks after its mixed.
Understanding the Problem: What Causes Watery Paint? Paint, whether oil-based or water-based, tends to separate when left unused for an extended period. The separation of the paint can lead to a watery consistency, with solid components settling at the bottom and the liquid rising to the top.
While you may not love the smell of fresh paint, spoiled paint has a scent that's much worse. "Paint that is beyond its shelf life can develop a rancid, sometimes rotten-egg odor," says Edrosa. If you open a can and find either of these problems, dispose of the paint and buy new.
When paint is too thick, it leads to problems during application and drying. Thinning paint reduces viscosity by adding more solvents, allowing for a smoother application and finish.
Too much or too little coating can cause quality issues. If the coating is too thin because not enough paint has been applied, then profile peaks may remain exposed and instant corrosion can take place.