All unfinished wood or bare wood surfaces should always be primed prior to painting. This goes for both interior and exterior paint projects. The reason you cannot skip bare wood priming is that wood is porous and has a grainy surface. Because primer contains high solids, it helps fill grains in the new wood.
Oil-based primers are ideal for interior and exterior unfinished or bare wood because they seal the porous surface of wood, enabling the coat of paint to better cover the surface. They stop tannins, released from woods, such as cedar or redwood, from bleeding through the surface of the paint.
Types of Paint to Use on Unfinished Wood Crafts
Latex paints are ideal if you are looking for general coverage with a fast-drying, durable finish. They work well on both interior and exterior surfaces. Acrylic paint for wood crafts have the same qualities as latex paints and can also be used on unfinished wood crafts.
You may or may not need more than one coat, depending on the paint type you choose. If so, it's vital to let the first coat dry properly first or you'll make an awful mess of it. As a general rule, two coats deliver a better sheen and a deeper, fuller finish than one.
Whether you are using lumber fresh off the market or refreshing an old piece of furniture, it is important to sand it first to remove any surface irregularities and the old paint. The goal is to prepare the wood to receive the new, fresh paint coat.
If sanding is your least-favorite step, then it's certainly possible to paint furniture without sanding. But to do so with favorite results, you should clean the wood's surface AND use a high-quality primer and/or paint.
If you are deciding to paint bare wood, you should seal all knots (spot prime) with a shellac based primer. Shellac based primers are great for sealing wood knots and sap streaks. They do carry a pungent odour, but dry very quickly and will not let the knot bleed through the top (finish) coat.
If you don't properly prepare the wood, moisture damage could destroy the wood, or natural tannins may bleed through the paint. Wood preparation is time consuming, but it's not overly difficult. With the right know-how, a novice painter can paint untreated wood surfaces for an even, clean, professional appearance.
The best rule to adhere to is to apply at least two coats of sealer directly onto the raw wood. This will protect the wood and create a barrier. Then apply primer to enhance adhesion, return tooth to the surface, and whiten the surface for optimising paint colours you plan to apply over it.
What happens if you don't prime bare wood is not pretty. Similar to new drywall, raw wood soaks up paint like a sponge. As a result, your surface will look blotchy since pores in the woodwork unevenly absorb the paint. More importantly, the painted wood will likely peel in two or three years without primer.
If you're painting wood without a stain or finish, use a latex or an oil-based primer for the best results. Don't over or under apply the primer: You should aim to apply two coats of primer to your wood's surface. Brush the primer on, and allow the first coat to dry completely before adding the second coat.
This interior and exterior primer is specially formulated to be a sound undercoat for paint and will help enhance the topcoat's performance. It has excellent adhesion to both interior and exterior surfaces including masonry, metal and excellent penetration for bare wood.
As a general rule, a primer is needed when the surface is either too rough, too uneven, not sealed yet, or when it is a surface that the chosen paint won´t adhere to properly. If no primer is used the paint might peel off, bubble up, or the final paint job might have slight discolorations.
However, if you are painting a brand new wood such as a door you will need a primer as the first coat to seal the wood ready for the undercoat. There are primer/undercoat paints that act as both, such as Dulux Trade Quick Drying Primer Undercoat that is ideal for a base layer or two on bare wood.
A paint and primer in one is not designed for every project. Some surfaces require specialty primers that block out color, have higher adhesion qualities or handle corroded surfaces. Exterior surfaces such as wood and metal require a primer for proper adhesion and blocking power.
Bare wood is not only porous, but because of its grain variations and the possible presence of knots or filler, absorbs at variable rates, and should always be primed.
Using a brush or roller and, moving with the grain, apply a thin layer of primer. Allow it to dry completely (sometimes up to 24 hours) before applying the paint. If any gaps remain, sand them and add a second cont of primer. Oil-based primers are good for sealing the porous surface of the wood.
To properly prep bare wood, first sand with 120-grit sandpaper to open the grain of the wood. Wipe the dust away, and then sand again with 120 grit. Next I wipe the dust away and then sometimes wipe the wood with a damp cloth to raise the fibers.
MINERAL PAINT (My Favorite Option)
It'll adhere to just about anything. As an added bonus, Fusion paints are so durable they are waterproof, stain resistant, and don't even require topcoat. I do recommend lightly scuffing the piece, but no heavy sanding is needed for best results!
New paint will not easily stick to a smooth surface. Thus, if you don't sand the paint job (at least a little bit), your paint will begin to flake and peel in no time at all. A little bit of surface roughness will provide the traction that is needed for the paint to stay in place.