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It is frustrating when you put a lot of time and effort into painting your home, only to see it peeling a couple of hours later. So what causes paint not to stick?
The five reasons that paint won’t adhere are because the surface is dirty, the paint or primer wasn’t mixed properly, there are high humidity levels, too much paint or primer has been applied, or the air temperature is too hot or cold.
This article will help you identify the cause of the problem and show you what to do to make the paint adhere.
5 Reasons for Poor Paint Adhesion
Here is a breakdown of the 5 main reasons for poor paint adhesion, starting with:
1. Dirty Walls
An obvious but often overlooked cause of paint not sticking to a wall or a door is grime. Oil from handprints, dirt, and food splatters will all form a greasy film on the surface and prevent the paint from sticking.
So, how do you make the paint adhere to a dirty wall? Even if you manage to get the paint to stick, the dirt is a haven for bacteria and mold, and it will show through your paint.
So, clean the wall before you begin painting. Dampen a cloth with warm mild soapy water and wipe down the whole wall.
In addition to removing the discoloration and superficial dirt, you should also remove any grease and oil that may have clung to the wall. The oil will stick to the cloth, so keep cleaning that area until the cloth glides smoothly over it.
If you want to use a stain remover, make sure it does not contain oil-based products. Other cleaning chemicals, such as silicon, will also interfere with the paint’s adhesion.
2. Poorly Mixed Paint or Primer
You will have read on the tin of your paint or primer that it needs mixing in with a thinner. The paint will specify that you should use around 15-25% water (or 5-10% mineral spirit for oil-based paint) for the first coat and to mix it in thoroughly.
If you do a bad job of mixing, you will find that the paint or primer will come off the brush in patches of varying thickness. You may even find that the roller has not landed any paint at all.
What is the best way of mixing paint or primer? Many people will try to mix the paint with an old stick, but this is labor-intensive and not fast enough to blend two fluids.
Buy a paint mixing attachment for an electric drill. This will mix the paint in under a minute and save your arms from aching.
Leftover unmixed paint will stick to the inside of the paint can. So, it is worth pouring your mix into another container for better mixing. Then use the mixer again to finish with a smooth mix.
3. High Moisture
High humidity is the enemy of paint adhesion. When warm, moist air clings to the cold surface of a door or wall, it causes the surface to reject the paint, and once the paint is dry, it begins to flake off.
This can happen on every surface in the summer, whether emulsion or gloss, and regardless of painting on ceiling doors, windows, or trims. But high humidity is more common in rooms with heated water, such as bathrooms and kitchens.
How do you make the paint adhere better in humid conditions? Before you start painting, you want to check if your paint will be battling humidity.
You can test for excessive humidity with a gauge or with the following process:
- Fill half a drinking glass with ice cubes.
- Wait 5 minutes.
- If the glass is clear, the humidity is low.
- If condensation starts running down the outside of the glass, the humidity is high.
If waiting for the weather to improve is not an option and you are painting an interior room, you can try using a dehumidifier. The best humidity for painting is between 40-50%. It is easier to judge the moisture content in the air with an inexpensive digital humidity gauge.
4. Over-Applied Paint and Primer
You may feel like the first coat did not cover well, and you are in a hurry to get the next coat on. But overpainting can cause similar problems to a dirty or humid surface.
With over-applied paint, you may see peeling or that the paint is not adhering to the surface and not leaving the roller or brush. This is a more frequent problem when using oil-based gloss paints on doors and trims, where the first coat leaves a smooth and shiny surface.
So, what can you add to the paint to make it stick better to the first coat? Wait longer before trying to apply the second coat.
The paint manufacturer will tell you to use a thicker mix on a second coat. For water-based paint, this can mean 15-20% water rather than 25%.
If the manufacturer tells you to wait 26 hours between coats, then wait. The drying time is specific for a reason, and if you go back too soon, you will just be pulling your first coat off the wall with your roller or brush.
The over-painted surface tends to cause paint to ball up on the brush or roller as you try to apply it. If your paint is peeling, you may have no choice but to scrape off everything and start again with a clean surface.
5. Cold Weather
If you struggle to work in the cold, you know how the paint feels. Paint prefers a drying temperature of between 40-90°F (21-32°C).
If it’s too cold, the paint won’t be able to dry fast enough, resulting in dripping. Also, bear in mind that if it’s too hot, the paint will peel. However, this is more of a problem with oil-based paints.
How do you fix the problem of paint not sticking in the cold? With the cold often comes humidity, and a cold surface is perfect for condensation, so you need to fix both issues.
If you are using a heater indoors, you need to ensure that you have good ventilation. Heating the room will speed up the release of fumes in the paint, which can be dangerous in an enclosed space.
If you are painting outside, avoid painting on overcast days or when it is freezing out. It is better to plan the day you are going to paint an exterior wall and give the paint a weather window of a full day to dry.
In general, it is better to wait till the summer to paint an exterior wall when you know that it is going to be warmer. You can use a heater indoors, but you need to stay aware of humidity levels and makes sure that they do not drop below 50% or go above 85%.