When you decide to use mineral stone paint, you are choosing a finish that behaves differently from standard synthetic coatings. It relies on a chemical bond with the substrate rather than just sitting on the surface like a plastic film. Because this paint is often thinner and more reactive, it demands a surface that is structurally sound and chemically compatible. If your wall preparation is poor, the mineral paint will highlight every single imperfection instead of hiding it. You must understand that the paint is only as good as the surface underneath it. If the substrate is crumbling, dusty, or covered in incompatible layers, the coating will eventually fail regardless of how expensive the product is.
Success in this trade comes down to the hours you spend before you ever open a paint tin. Most people focus on the final colour, but the real work happens in the cleaning, filling, and priming stages. You are essentially creating a canvas that must be uniform in both texture and absorption. If one part of the wall drinks paint faster than another, your final finish will look blotchy and uneven. By following a rigorous preparation process, you ensure that the mineral particles bond correctly to the surface. This creates a durable, long lasting finish that can withstand the elements for many years. Think of this work as the foundation of your project, because skipping a step now will only lead to expensive repairs later.
Before you pick up a sander, you need to identify exactly what you are working on. A wall made of fresh render behaves entirely differently than a wall painted a decade ago with synthetic gloss. If you are dealing with new plaster or render, you must allow it to cure fully. Mineral paints need a porous surface to grip, so any residual moisture or chemical salts will ruin the bond. You should wait at least twenty eight days for new render to dry and reach a neutral pH level. If you are unsure, use a moisture meter to ensure the reading is below ten percent before you even consider applying a primer.
If you are painting over old surfaces, you must determine what is already there. Old emulsion paint is usually fine if it is stable, but you must scrub it to remove loose chalky residue. If you find old gloss or oil based paint, you cannot apply mineral stone paint directly to it because it will not stick. You have to remove the sheen by sanding the surface until it is dull or use a strong adhesion primer. Concrete walls are often very smooth or contain release agents from the formwork, which act as a barrier to paint. You must clean these thoroughly, potentially using a light acid wash or a mechanical grinder, to open the pores of the concrete. Never assume a wall is ready just because it looks clean.
Filling cracks and holes is a task that requires patience and a good eye for light. When you apply a mineral stone paint, any hump or ridge will become magnified by the unique texture of the finish. You must fill every defect, but the key is to sand it back until it is perfectly flush with the surrounding area. If you leave a raised patch, the light will hit it and create a shadow, making your repair look like a scar on the wall. Use a fine grit sandpaper, starting around eighty grit for the initial cut and finishing with two hundred and twenty grit for a smooth transition. Always use a light at an angle to highlight irregularities you might otherwise miss.
After sanding, you must remove every trace of dust. Mineral paint is sensitive to surface contamination, and any loose dust will act as a barrier, preventing the paint from anchoring to the wall. Use a damp cloth or a vacuum cleaner to clear the area, then wait for it to dry completely. If you are dealing with deep cracks, do not simply smear filler over them. You must open the crack into a v shape with a scraper, clean out the debris, and then fill it in thin layers. This prevents the filler from shrinking and cracking again later. If your walls are riddled with deep divots or crumbling areas, you might need to apply a skim coat of thin plaster across the entire surface rather than trying to patch individual spots.
One of the most common causes of failure in exterior painting is the presence of failing old layers. If you have paint that is peeling, flaking, or bubbling, you must remove it entirely. Use a wire brush or a scraper to test the edges of any loose paint. If the paint comes away easily, it has lost its bond with the substrate and will continue to fail. You should strip these sections back until you reach solid material. If the entire wall is covered in layers of old, brittle paint, it is often more efficient to use a pressure washer or a mechanical sander to strip it back to the original surface.
Once you have removed the loose material, you must address the edges of the remaining paint. If you leave a sharp ridge where the old paint stops, it will show through your new mineral finish. Sand the edges of these patches until they are tapered and smooth. If you find that the old paint is chalky, you should wash the wall with a mild detergent and water. Let it dry, then perform an adhesion test. Apply a small square of tape to the wall, press it down firmly, and rip it off quickly. If the old paint comes off on the tape, you cannot paint over it. You have to remove it or seal it with a heavy duty binding primer.
Moisture is the silent enemy of mineral coatings. If you paint over a wall that contains high levels of moisture, the water will try to escape through the paint film as it evaporates. This can cause the paint to blister, peel, or push salts to the surface. Salt efflorescence is a white, powdery deposit that appears when moisture carries minerals out of the masonry and deposits them on the exterior. You must treat this before painting. Brush off the salts with a dry, stiff bristle brush, then wash the area with clean water. If the salts keep reappearing, you have a deeper moisture problem that needs to be solved at the source, such as a leaking gutter or a cracked flashing.
Never paint during periods of high humidity or when the temperature is dropping toward freezing. Mineral stone paint needs consistent conditions to cure properly. If you are working in humid coastal areas, you need to be especially careful about drying times. A wall might feel dry to the touch but still hold significant moisture within the pores. If you are working on a building that has been damp for a long time, consider using a moisture meter to check the depth of the masonry. If the wall feels cold and damp, wait for a few days of dry, breezy weather before proceeding. Remember that the paint will not protect the wall if the wall is already saturated with water.
The primer acts as the bridge between your prepared wall and the mineral paint. If you are working on porous surfaces like fresh render or old, thirsty brickwork, you need a sealer primer. This product reduces the suction of the wall, ensuring that the paint sits on the surface rather than soaking in. Without a sealer, the first coat of paint will disappear into the wall, leading to a patchy finish and wasted product. Use a ratio of one part primer to two parts water if you are using a concentrated sealer, but always follow the manufacturer instructions for your specific product. The goal is to create a surface that is uniform in its absorption.
If you are painting over surfaces that have been repaired with filler, you must use a uniform primer. This hides the difference in texture and porosity between the filler and the original wall. Without this, your paint will dry at different rates over the patch, creating a visual ghosting effect. If you are working on non-porous surfaces like old gloss paint or dense concrete, you need an adhesion primer. These products contain resins that stick to smooth surfaces, providing a mechanical key for the mineral paint to grab onto. Never skip the primer. It accounts for a very small share of your total budget, but it is the most important component for the longevity of the finish.
Masking is the step that separates a messy amateur job from a professional result. You must protect every surface that you do not intend to paint, including window frames, glass, door hardware, and flooring. Use high quality masking tape that is designed for exterior use, as cheap tape will leave a sticky residue that is impossible to remove once the sun hits it. Apply the tape firmly, pressing the edges down with your thumb to ensure a crisp line. If you are working around intricate details, use a flexible masking product that can curve around shapes without lifting.
Lay down drop sheets or heavy duty plastic to protect your floor or walkways. Mineral paint can be difficult to remove once it dries, especially if it lands on porous stone or timber. If you are working at height, make sure your protection covers the entire area beneath your scaffolding or ladder. Remove the masking tape while the paint is still slightly damp, or use a sharp blade to score the edge of the tape before pulling it away. This prevents the paint from pulling off the wall along with the tape. A clean, protected site allows you to move faster and prevents the frustration of cleaning up drips and splashes at the end of the day.
There are times when the condition of the wall is simply beyond the scope of basic preparation. If you find large structural cracks, crumbling mortar joints, or deep areas of rot, you need a professional plasterer or mason. A good rule of thumb is that if a crack is wider than five millimetres, it could indicate a foundation issue or a structural failure that paint will not fix. A plasterer can patch these areas properly, using compatible materials that will stand up to the weather. If you try to cover up a structural defect with paint, it will only reappear within a few months, wasting all your time and material.
You should also consider calling in help if you have a massive area to prep or if the wall is in a very poor state of repair. A professional team has the equipment to clean, sand, and prime a large surface area in a fraction of the time it would take you. They can identify hidden issues, like trapped moisture or chemical reactions in the substrate, that might not be obvious to an untrained eye. If your wall is crumbling or has been patched fifty times by previous owners, a full skim coat by a professional is often the most cost effective way to achieve a high quality finish. Do not be afraid to admit when a project requires specialized skills.
Before you open the first tin of paint, run through a final mental checklist to ensure you have covered every detail. Is the wall completely dry? Have you removed all the dust? Is the surface uniform in its absorption? Have you checked the weather forecast for the next forty eight hours? Ensure you have enough brushes, rollers, and masking tape on hand. It is a common mistake to run out of supplies mid-project, which leads to messy breaks and visible lines in the finish. Make sure your scaffolding or ladder is secure and that you have a clear path to work around the structure.
Check your primer levels and ensure you have mixed enough to cover the entire area in one go. If you are mixing colours or batches, do it all at once to ensure a consistent shade. Take a final walk around the building and look at the walls from different angles. Do you see any remaining patches, ridges, or loose debris? If you see it now, you will definitely see it once the paint is on, so take the extra hour to fix it. Being disciplined during this final stage is the difference between a project you are proud of and one you want to hide from your neighbours.
Planning your material needs is a critical step that prevents waste and ensures you have enough paint to finish the job without stopping. You need an accurate measurement of your total wall area in square metres. Remember to subtract the area of doors and windows, but add a small percentage, usually around ten percent, to account for waste and absorption. Mineral stone paint has a specific coverage rate, usually expressed as square metres per litre, which you can find on the product label. When calculating your quantities, always factor in the number of coats required by the manufacturer. Most mineral paints require at least two coats for full opacity and protection.
If you are unsure how much paint or primer you need for your specific surface type, Frelux provides specialized calculators and estimators that allow you to input your wall dimensions and substrate conditions. These tools help you determine the exact quantities of primer and paint required for your project, reducing the risk of buying too much or running short halfway through. Using these resources ensures you have a clear understanding of the material ratios needed for a professional finish. By planning your quantities accurately, you keep your project on budget and ensure that your final result is consistent, durable, and perfectly prepared for years of service.