how to paint a door or wood using acrylic or oil based paint and how to use the brush
What do most people do wrong?
Most people do not prepare the surface properly. First - please read my article on sanding. Although paint is basically glue with pigment - it will not stick to dusty or loose surfaces because the bonding of the paint with the painted surface will only be as strong as the dust. Similarly, water based paint will not stick to oily spots, and oil based paint will not fix to wet surfaces.
Preparation is, therefore key. Expect to spend up to 5 times as long preparing the surface compared to actually painting it. A new surface is easier, but there are still steps to follow.
Painting is quite hard work, and how you hold the brush will affect the result and how quickly you get tired. Hold the brush with the handle resting between the thumb and forefinger so you can grip the wide part. Use your whole arm from the shoulder down to make the strokes.
Now we will go into more detail:
Preparing a new surface.
Even a new surface will need a light sand. Use non-clogging fine paper, and give it the once-over - sanding with the grain to get all the high spots off.
For water-based paint, rub the surface with a rag and methylated spirits. Under no circumstances do this near a spark or flame of any kind as it is highly flamable, and the flame is invisible. Used rags should be hung open from a line to dry out - do not let them sit screwed up in a bundle. Methylated spirit is water soluble which is why it's ok to use it for water based paint.
For oil based paints, use white spirit and follow the same precautions as above.
Only paint within the specified temperature and humidity range. It is noted on the tin; and only paint in a dust-free atmosphere away from annoying bugs that will otherwise land and stick on.
No matter what the "tin" says, a three-part application will be best and last for decades. THe first coat is a primer. The purpose of the primer is to soak into the wood and provide the best possible bind between then wood and the undercoat. Slightly thin the primer with a little water or white spirit as appropriate. This will allow it to go on thin - and you need to put it on very thin. A thick coat of primer is not strong while a thin coat does the job of providing a good base for undercoat. Allow it to dry completely, but not in full sun in case is goes chalky.
The undercoat is formulated chemically to bind well with the primer, and to provide an excellent surface for the top coat. Do not miss out this step. Again - a very thin coat is all that is required - and only one coat should be used.
Now appy three very thin top coats. No matter how you approach the job, three thin coats will be much better than two thicker ones, and don't even think about trying to trowel-on a single coat and get away with it.
Each coat needs to dry properly, then use wet-and-dry very fine sanding paper with a little water to key the surface and remove bumps and blips. Clean the surface after each sanding as noted above.
Next - we will talk about painting technique to avoid drips, runs and get a smooth finish.
Preparing an old surface.
If the old paint is flaking, then remove it. Sand the remaining surface as flat as you can get it, and fill cracks and dents with something like water-putty or some other sandable and paintable filler. Run your hand over the surface to find imperfections. A good trick is to glance a strong light at an oblique angle onto the surface. Dents and bumps will show up as strong shadows.
All nails should be punched below the surface and filled with an oil-based filler to prevent oxidation. All filler needs priming, as does bare wood patches.
This preparation is essential, and can often take a lot more time than the actual painting, but the end result is worth the trouble.
Order for painting a panel door
How to apply paint with a brush
Pick a brush with long soft, fine bristles that do not fall out. Basically this means, "Spend a decent amount of money and buy a good one." Cheap brushes give a cheap finish.
Stir your paint very well with a broad and flat stirring stick. This is essential. Do not 'beat it', just stir and pull the stick up and down as you do it to distribute the binder and the color. Now strain it through a nylon stocking into a clean paint tin.
Tape a stick across the top of the paint tin.
Load the brush by dipping it about 1/3 of the way up and wipe both sides against the stick to get rid of excess paint. By using the stick and not the side of the tin, the paint will fall into the tin and not stick to the sides. This is cleaner and it prevents drying clumps of paint.
Dab the paint throughout the area that you are going to paint. For a typical 3" brush, you can probably cover about 2 square feet with one load.
Use ONLY the tips of the brush. Do not drag the bristles along the surface. This means that you hold the brush perpendicular to the surface - or nearly so. Now make alternate horizontal AND vertical strokes until the paint covers that area. Make it a thin coat, and if there is still too much paint, spread it further. Only by evenly distributing the paint will you get a consistent result.
The final phase is to make long slow strokes with the very tips of the bristles, but only very gently touching the surface. You are aiming to just tickle the surface of the paint. All brush marks should vanish. This is the key to getting a good finish. It is called laying off or laying out.
Keep a wet edge:
Keep as few edges as possible because you have to feather into the place where your paint application stopped. This means that you should try to paint a full width or a full height where possible. Don't let that edge dry before applying the next section. Therefore, start in the top left corner for a right handed person and top right for a left handed person. On a large flat area, work about a 2 foot area at a time. Each time an area is finished - lay it off as described above. This wet-edge technique is most important with epoxy or oil based enamel under windy conditions because it forms a skin very quickly. Once it goes tacky, do NOT try to brush it out, it will just get worse. A small amount of linseed-oil for enamel paint on the LAST coat only will improve the finish, but it retards the drying time significantly. Use about 1 teaspoon per litre.
Clean the brush very well and wrap it in cling-wrap ready for next time.
For a panel-door do the following:
- Inside panels.
- Horizontal boards.
- Vertical boards - and feather in the join with the horizontal boards.
Work top left to bottom right or top right to bottom left.
If you apply three very thin coats, then you won't have a problem with drips, brush marks or slow drying time.
After each coat is very dry, sand lightly as noted above. The technique you should use is to choose very fine non clogging paint-friendly paper, and just do one or two strokes. This is all that is required to key the surface and get rid of any small bumps.