primer

Primer is a term with several related uses in painting, chemistry, biology, education, and cosmetics. In painting and coatings, a primer is a preparatory layer applied to a surface before paint or varnish to improve adhesion, even out porosity, block stains, and enhance durability. Common types include oil-based, acrylic, and shellac primers, used on wood, metal, plaster, and previously painted substrates.

In firearms and ammunition, a primer is the small explosive component that ignites the propellant when struck or sparked. Primers are cartridge-specific and can be centerfire or rimfire, forming the ignition source for the cartridge.

In molecular biology, a primer is a short strand of DNA or RNA that provides a starting point for DNA synthesis. Primers bind to complementary sequences flanking a target region, enabling amplification by techniques such as polymerase chain reaction (PCR) or sequencing. They determine the specific region copied and influence efficiency and specificity.

In education and publishing, a primer is a basic introductory text used to teach fundamental skills, most notably reading and literacy. Historically, primers presented simple letters, syllables, and words to young learners.

In cosmetics, a makeup primer is a preparatory product applied to the skin before foundation to create a smoother surface, reduce the appearance of pores, and extend makeup wear.

Across these senses, primers serve as foundational agents that prepare a substrate, signal a starting point, or introduce foundational knowledge.