Elena Rossi
Painting over pre-painted surfaces can be a tricky business. While it is possible to paint over old paint without priming, this is not always recommended, especially if you are covering a light colour with a darker shade, or if the wall has stains or imperfections. In such cases, using a primer can save you time and money by providing a smooth base for your new paint and preventing the old colour from bleeding through. However, if the new coat is the same type as the old paint (both oil-based, for example), and the wall is smooth and clean, you can simply pick your new colour and get painting!
Characteristics and Values Table
| Characteristics | Values |
|---|---|
| Primer required | If the wall is smooth, clean, and the paint type is the same (e.g. both oil-based), a primer may not be needed. However, if covering a latex paint with oil-based paint, filling holes, or covering a bright colour, a primer is recommended. |
| Number of coats | Two coats of primer are generally recommended for adequate coverage and adhesion. The number of coats of paint depends on the colour change and coverage required. |
| Surface preparation | Sanding, filling holes, and ensuring a smooth surface are important steps before applying primer or paint. A drywall pole sander can be used for larger areas. |
| Paint type | Premium acrylic paints can be applied directly over oil-based coatings with proper preparation. Tinted primers can help with coverage when changing colours. |
| Adhesion | Primers help improve adhesion and prevent the old colour from bleeding through. |
| Cost | Primer is generally less expensive than paint. Using a primer can reduce the number of coats of paint needed, saving costs. |
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What You'll Learn
Using primer paint to cover old paint
When it comes to using primer paint to cover old paint, there are a few things to consider. Firstly, it is important to determine the condition of the wall or surface you are painting. If the wall is in good condition and the paints are chemically the same (for example, both latex-based), then you may not need to use a primer at all. In this case, you can simply apply one or two coats of the new paint, depending on the colour change and coverage desired.
However, if the wall is in poor condition or if you are dealing with a significant colour change, using a primer can be beneficial. A primer can help to cover the old colour and create a uniform base for the new paint to adhere to. This is especially useful if you are painting over a dark colour with a light colour, as it can reduce the number of coats of paint needed. For example, if you are painting over an old, oil-based paint, a primer can help to seal and cover the old paint, providing a better surface for the new paint to adhere to.
It is worth noting that some modern paints are marketed as "paint and primer in one". These paints claim to provide the benefits of both paint and primer in a single product. However, it is generally recommended to still apply two coats of these paints for optimal coverage and to meet warranty requirements. Therefore, it is important to read the instructions and understand the limitations of these products before use.
When using a primer, it is important to prepare the surface properly. This may involve sanding or rubbing down the old paint to create a smooth base for the primer to adhere to. Any residue should be removed, and if there is any bare wood or metal, it should be primed before applying the undercoat and topcoat.
Overall, using a primer can be a helpful step when covering old paint, especially when dealing with significant colour changes or poor wall conditions. It can save time and money by reducing the number of coats of paint needed and providing a better base for the new paint to adhere to. However, it is not always necessary, and the decision to use a primer will depend on the specific circumstances of your painting project.
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Sanding down old paint
When sanding down old paint, it is important to use the right tools and techniques to ensure a smooth and even finish. Here are some steps to follow:
- Start by assessing the condition of the old paint. If it is heavily damaged or peeling, it may be necessary to use a paint stripper or heat gun to remove the majority of the paint before sanding.
- Choose the right type of sandpaper for the job. For most projects, coarse grit sandpaper will be the best option for initial sanding. Finer grit sandpaper can be used for final surface preparation after the majority of the paint has been removed.
- Attach the sandpaper to a sanding block or power sander. Power sanders, such as the ROTEX eccentric sander, can make the process faster and more efficient, especially when working on large surfaces like walls or old windows and doors.
- Begin sanding in a consistent pattern, following the direction of the wood grain if applicable. Apply even pressure to ensure that the paint is removed evenly.
- Continue sanding until the majority of the paint has been removed and the surface is smooth to the touch. Pay extra attention to corners and edges to avoid rounding over these areas.
- Finish up with a final light sanding using finer grit sandpaper to create a smooth base for the new paint. Remove any dust from the surface with a tack cloth or vacuum before proceeding with priming and painting.
It is important to note that sanding can be a time-consuming and labour-intensive process, especially when working with thick or multiple layers of paint. Additionally, it is crucial to prioritize safety when sanding, as paint dust can be hazardous. Always wear a respirator and eye protection, and ensure the work area is well-ventilated.
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Using paint and primer in one
Paint and primer in one, or self-priming paint, is a paint with primer mixed into it. It is a great option for many DIYers looking to save time when painting the interior or exterior of a home. This type of paint works well for many projects, but it isn't suitable for every job, depending on the type of surface you need to paint.
Self-priming paint is ideal for re-painting a wall in the same colour, as you do not have to worry about colour bleed-through. It is also suitable for new, unfinished drywall, as it eliminates the need to prime separately.
However, self-priming paint is not suitable for raw surfaces such as raw wood, bare drywall, metal, or cement, or with glossy surfaces such as new cabinets or oil-based woodwork. These surfaces require a separate primer to seal them and ensure proper adhesion.
Some disadvantages of using paint and primer in one include the higher cost and the possibility of issues with adhesion or bleed-through, requiring the purchase of additional primer and paint to fix any mistakes.
It is important to analyse the project and consult a paint expert before deciding whether to use a paint and primer in one product.
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Painting over oil-based paint
Oil-based paints were popular decades ago for use on high-impact areas like trim, cabinets, and doors due to their toughness, self-levelling, and flawless finish. However, they contain harmful VOC chemicals, so most people now use water-based and latex paints.
If you are painting over oil-based paint, you must first identify what type of paint it is. To do this, rub a cotton ball soaked in denatured alcohol on the surface. If the paint comes off, it is water or latex-based paint. If not, it is oil-based.
If you are painting over oil-based paint with another oil-based paint, ensure that the existing coat is fully cured. If the coating is over seven to 30 days old and can be scrubbed without affecting the finish, consider it cured. If the existing natural oil-based coating hasn't cured, only use a natural oil-based paint to cover it. To cover an alkyd paint that hasn't cured, use an alkyd or a natural oil-based paint.
If you are painting over oil-based paint with water-based paint, you must properly prepare the surface. First, sand the surface with fine-grit sandpaper (180-220 grit) to remove the gloss from the surface. Scrape off any chipped or peeling paint and fill cracks or dents with wood putty. Once the filler is dry, sand it smooth with the fine-grit paper. Then, clean the surface with trisodium phosphate (TSP) to pick up any dirt or dust left behind from the sanding. Mix a quarter cup of TSP with a gallon of warm water, saturate a sponge in the solution, and wipe down the surface. Make a second pass over the cleaned surface with a sponge dampened in fresh water, then let the surface air-dry.
Once the surface is clean and free of dust and debris, apply a coat of bonding primer. A coat of oil or water-based primer will help the paint adhere better to the surface and prevent it from peeling or chipping. Allow the primer to fully dry. When using water-based paint over oil-based paint, always prime. To prevent peeling and chipping in the drying and curing phase, use a bonding primer—formulated to stick to glossy and other hard-to-paint surfaces. Apply one to two coats of an oil-or water-based bonding primer and dry according to product directions. You’ll know the surface is adequately primed when the former paint colour, stains, and other surface imperfections are no longer visible.
After priming, apply at least two coats of a high-quality water-based latex or acrylic paint over the primed surface, allowing ample drying time according to the product directions between coats. If painting interior features (e.g. kitchen cabinets), choose a paint labelled for "interior" use. Paints labelled "interior/exterior" hold up better to rot and extreme weather, so are desirable for painting exterior features (e.g. the front door). If you’re painting molding or other trim, choose a complementary colour and a semi-gloss sheen to accentuate the details on the trim.
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Painting over glossy paint
Step 1: Prepare the Surface
Start by clearing the area of any furniture or obstructions. Use dust sheets to protect the floor and adjacent surfaces from paint splatters. Apply decorator's tape to areas such as light switches, skirting boards, and walls below cornices to ensure clean paint lines and protect these surfaces. Ensure the room is well-ventilated to manage paint fumes.
Step 2: Clean the Glossy Surface
Use a mild detergent solution, such as sugar soap, and a clean sponge to wash the glossy surface. This step is crucial to removing grease, dust, and dirt that can interfere with paint adhesion. Work in small sections to ensure a thorough cleaning. Rinse the surface with clean water and a rag to remove any detergent residue, as this can cause patchiness in the final paint job.
Step 3: Sand the Surface
Lightly sand the glossy surface using sandpaper or a pole sander for larger areas. Sanding creates micro-scratches in the glossy finish, providing a rough texture for the new paint to adhere to. Aim for a consistent scratch pattern across the surface, ensuring more of the wall is scratched than glossy. Use a grit level of 120-180 if you plan to prime the wall, and 220 if you intend to paint directly.
Step 4: Apply Primer
Priming is essential when painting over glossy surfaces. Choose a primer suitable for the surface, such as a specialist wood primer for skirting boards or cornices. If the previous paint job is oil-based, use an oil-based primer; otherwise, a standard primer will suffice. Apply one or two coats of primer, following the manufacturer's instructions, and allow it to dry thoroughly.
Step 5: Paint
Finally, apply your chosen paint over the primed surface. Depending on the colour change and the type of paint, you may need one or more coats. Follow the paint manufacturer's instructions for the best results.
Remember, proper surface preparation is critical to ensuring the new paint adheres well and results in a durable and aesthetically pleasing finish. Take your time with each step, and don't be afraid to seek advice from paint professionals if needed.
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Frequently asked questions
If the wall is smooth, clean, and covered with the same type of paint (e.g. both oil-based), you can directly apply the new paint. However, if you are covering a latex paint with a new oil-based paint, you will need to use a primer.
Applying two coats of primer is ideal as it will allow your new paint to bond to the wall properly.
Using a primer will ensure a smooth and consistent base layer for the coloured paint. It will also prevent the colour of the paint underneath from bleeding through the new coat.
