A grain filler (pore filler or paste wood filler) is a

woodworking Woodworking is the skill of making items from wood, and includes cabinetry, furniture making, wood carving, joinery, carpentry, and woodturning. History Along with stone, clay and animal parts, wood was one of the first materials worked b ...

product that is used to achieve a smooth-textured wood finish by filling pores in the wood grain. It is used particularly on open grained woods such as

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

mahogany Mahogany is a straight- grained, reddish-brown timber of three tropical hardwood species of the genus ''Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: Universit ...

and

walnut A walnut is the edible seed of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. They are accessory fruit because the outer covering of the fruit is technically an i ...

where building up multiple layers of standard wood finish is ineffective or impractical.

Composition

Grain fillers generally consist of three basic components; a binder, a bulking agent and a

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

. The binder is wood finish, and in the case of oil-based fillers is typically a blend of oil and

varnish Varnish is a clear Transparency (optics), transparent hard protective coating or film. It is not to be confused with wood stain. It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmente ...

. In the case of water-based fillers, it is acrylic or urethane. The type of binder influences the type of solvent used; oil-based fillers usually use mineral spirits, while water-based fillers use water. Both types of filler use

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

as a bulking agent as it resists shrinking and swelling in response to changes in

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

and

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

. Other bulking agents may include quartz powder,

wood flour Sawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sandpaper, sanding, Milling (machining), milling and Router (woodworking), routing. It is composed of very small chips of wood. These operations ...

, and talc.

Use

Woodworkers will use a grain filler before applying other finishes to open grained woods to achieve a "full finish", which is

mirror A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera ...

-like. Woods such as ash,

and

fall into this category, while tight grained woods such as

maple ''Acer'' is a genus of trees and shrubs commonly known as maples. The genus is placed in the soapberry family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated si ...

and

cherry A cherry is the fruit of many plants of the genus ''Prunus'', and is a fleshy drupe (stone fruit). Commercial cherries are obtained from cultivars of several species, such as the sweet '' Prunus avium'' and the sour '' Prunus cerasus''. The na ...

can achieve a full finish with just a few coats of finish. Before application, the surface is sanded and puttied to conceal surface imperfections, which would otherwise be made far more obvious by the grain filler. The filler is brushed on both with and against the wood grain and the excess is scraped off. After some drying, the woodworker typically uses a piece of burlap to remove more excess.

References

{{reflist Wood finishing materials