What Is an Acrylic Undercoat Paint?

Sealers

• Apply sealers to interior porous materials you plan to finish with acrylic products to seal the porosity and wood grain. This will keep your subsequent applications of paint or varnish materials from soaking into the surface and leaving a blotchy look to your finish coats. Sealers are also used to cover stains that might bleed into the paint from knot holes, pipe or nail rust or cigarette tars. Some sealers for wood are designed to raise wood grain so it can be sanded when dry. Preferred sealers for most applications tend to be alcohol or oil solvent based but can be covered with acrylic varnishes when dry. Oil-based sealers take longer to dry but absorb best into the material. They react badly with concrete and masonry and actually turn to soap so you need an alcohol-based product for concrete and brick.

Primers

• Primers form a bond to the surface to be painted or varnished in a way that paints cannot. You should always prime new surfaces of any kind before painting. You can buy them in water-based formulas most often used on new drywall. Oil-based alkyds are still preferred by most painters for wood surfaces but you may have trouble buying them in some states because of environmental regulations and water-based primers may be your only options. Alkyd films can be painted over with either oil-based or water-based finishes. Primers come in different densities. You should choose high-bond and high-density options for any imperfect situations like damaged sheetrock, for example.

Undercoats

• Undercoats are used on previously primed or painted surfaces because they are cheaper than paint and because they are specifically designed to adhere to the layer underneath them. You should use them when making dramatic color changes or covering previously gloss surfaces. Oil finishes will not to stick to latex acrylic surfaces and you will get better adhesion of latex over a prior oil painted surface if you apply an oil solvent-based alkyd undercoat over either before switching --- an alkyd surface is the great equalizer. If you apply them with care, enamel underlays (another common word for undercoat) form a suitable surface for applying semi- or even high-gloss acrylics to woodwork.

Hybrid Products

• Sealers, primers, and undercoats have been hybridized together into nice combination products. Most professional painters recommend and use a combination primer-undercoat and two coats of finish --- usually with high acrylic content if your budget allows. The first coat of finish serves as the undercoat. Beware of claims of primer and paint in one though. You will be disappointed. And remember your best choices of products and knowledge is a real paint store.