One well-applied mist coat is generally sufficient.
A mist coat should be left to dry for around 24 hours, even if it feels dry before this. Only one mist coat should be needed, but if you have some paint leftover that's already been watered down, you might want to add a second mist coat. As long as the first coat was dry, two mist coats will do no harm.
Leave the mist coat for 24 hours to dry. A simple test to see that the mist coat has worked is to use masking tape. If it comes off the wall clean, you're ready to go. A mist coat needs to be absorbed by new plaster so it needs to be pretty thin, almost like a thin soup.
Usually anything between 20 and 50% water on the miss coat is perfectly fine. Unfortunately there is no way to find out if you did it properly and there is no way to redo this. 15% would be too little water as the newly plastered walls needs to ``breathe'' in order to properly apply the next coat(s) over the miss coat.
A mist coat will usually take around 24 hours to dry, but drying times will vary depending on temperature and humidity. The mist coat should be dry to touch before you paint over it.
What happens if the mist coat is too thick? If the mist coat is too thick, it won't absorb into the plaster properly, which can lead to issues with adhesion.
Applying the second coat too early will result in lost time, money, and effort. Not only that but it'll also create additional stress that's not necessary. Applying the second coat too early will result in streaks, peeling paint, and uneven color.
There are two different ways you can apply the mist coat. If you choose to use a roller, you'll cover the wall much quicker but it will be very messy as rollers can splatter paint very easily. Alternatively, a paintbrush will take much longer but you shouldn't have as many drips to deal with.
If the mist coat is stuck to the back of your top coat colour then this will give you a clue that there is an issue with the adhesion. The best thing to do is sand this area back to the plaster, then usually it's just a case of following the steps above again after ensuring the plaster is totally dry.
Without the mist coat you're likely to have very poor adhesion between your paint and your plaster and quite often it will crack, flake or even peel off in sheets in some instances!
Mist coat paint is simply watered-down emulsion paint, which acts as a primer. All you need to do is get some white emulsion paint and thin it out with water. Three parts paint to one part water should do the trick. As an alternative to watering down your paint, you can also use Dulux Sealer for Plaster.
You only need one layer of mist coat before applying your normal emulsion, which should be applied in 2-3 layers. In terms of the mist coat drying time, you should leave the mist coat for 24 hours to allow it to set perfectly.
A well-chosen coat must neither be too short nor too long. The coat length should be based on the size of the body. A good guide is the rule that the hem should preferably end a hand's breath above the knee.
While one coat can save you both time and money, it may not fully cover the surface or provide the same durability as multiple coats. Therefore, it's not recommended for high-traffic areas, such as living rooms or dining rooms, where the walls are prone to wear and tear.
Why is my mist coat not sticking to plaster? This might be down to a couple of things. There might be dust on the walls, creating a barrier. Your plaster might be too polished, in which case you might need to abrade it, or go with a different primer.
To speed up the hardening process for larger amounts of paint, add some sawdust, cat litter, soil or sand to the cans and leave them to solidify. Once the paint is hard, you can take it to your local household waste and recycling centre to be disposed of appropriately.
As mist coat is of a watery consistency, it's perfectly normal for it to look patchy once it's dried down. But as it's only purpose is to seal the plaster and prep the surface ready for paint, a patchy finish is nothing to worry about.
All you need to do is dilute some emulsion paint with water and apply it to the plaster using a roller, paintbrush or spraying. One mist coat should suffice, but you can apply a second (or even third) coat just for extra peace of mind.
Conclusion. Sanding between coats of paint is a valuable step in the painting process that can greatly enhance the quality and longevity of your paint job. It helps to create a smoother and more professional-looking finish by eliminating imperfections and ensuring better paint adhesion.
You don't want to be too thin, but a mist coat needs to be thin—almost like a soup. The water will not seep into the substrate if the mist coat is too watery. As a result, your finishing coat will eventually start to flake or peel and the mist coat won't function as a bonding agent.
In contrast to watering down paint, “thinning” paint is a regular practice for all painters and is recommended by the paint manufacturer. To “thin” paint, an exterior painter will add water to the paint bucket, increasing the paint's workability and slowing down the speed with which it dries.
When the plaster is a uniform, pale colour then it has dried out and is ready to paint – the drying time varies according to the thickness of the plaster and the temperature of the room, but typically takes 3-6 days for a well heated room but particularly deep areas can take longer to dry.
Recoat Time for Oil-Based Paint
Water-based paints dry considerably faster than oil-based paints because the water evaporates to let the paint dry. Oil-based paints contain no water. Though oil-based paint may feel dry after only a few hours, it's best to wait a full 24 hours or more before applying additional coats.
Applying the second coat of paint before letting it adequately dry will result in your paint peeling, clumping, and bubbling. It can also result in a different colour than what you intended.