Wood Finishing 101 – Stains

Stains-   Most wood is stained prior to clear coating if it’s not going to be painted. Occasionally there are jobs which have a natural finish (no stain) but for the most part, some sort of stain is applied. The end use and appearance will determine the best type of stain to be used.

Non-Grain Raising (NGR) stain: They are usually dyes dissolved in an alcohol, usually ethyl alcohol. They are spray applied only and very fast drying. In most cases, they will be encountered in the furniture industry or cabinet industry. They are usually used to change the color of the wood prior to application of another, type of stain. For example, on maple, a relatively dense wood that where a very dark color is trying to be achieved, an NGR should be applied to get 60-70% of the desired color. After that application, usually a wipe stain is then applied. This accomplishes a couple of things. First, a dark color can be achieved without threat of inadequate adhesion and second, an often desirable appearance with “depth” is evident. They are not used as a stand-alone stain.

Sap stains and equalizing stains: These are dyes stains, again usually in an alcohol, used on only certain portions of a piece of work, typically only to change the color of isolated areas of the substrate. For example, if you had a greenish streak in a piece of maple or poplar, a reddish sap stain might be applied only to that streak. An equalizing stain on the other hand would be applied to everything but that greenish streak. As above, these are used as only a step in the staining process and another type of stain needs to be applied over these. These stains are usually only seen in the furniture industry. 

Dye stains: These are similar to both of the above but are used as the only stain. A typical application might be for window blind slats. They aren’t the best looking stains but depending upon the application and type of wood, could be acceptable. These types of applications are often dip applied and therefore the solvent blend is usually slower than the above stains.

Spray stains (solvent and water): These are blends of colorants in an appropriate base which is usually fairly quick drying. They allow for a quick staining process (higher volumes). Most millwork and door shops use these types of stains. As their description implies, they must be spray applied.

Wipe stains (solvent and water): These are blends of colorants in an appropriate stain base which provides a relatively long “open” time in order to allow for wiping of the stain. They are usually spray applied with a very wet coat. The time allowed before wiping (open time) can vary from just a few seconds to several minutes. They should be allowed to dry completely before applying a seal coat. Most cabinet and furniture manufacturers use these types of stains as they enhance grain definition and provide more “warmth and character” than spray-only stains.

Stain concentrates: These are typically solvent based only. They are mostly straight tint pastes along with a varying amount of stain base (not reducer). The end user will reduce with an appropriate stain reducer (spray type or wiping type) to achieve a desired color strength.

UV stains: These are stains which are used for applications beneath UV curable coatings. They are very unique in regard to stain base and colorants. They are usually highly specialized applications. They are often necessary to insure adequate adhesion and performance of the UV curable clear coats.

Up next “Where do we use these Conversion Varnishes?”

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