Architectural paint and stain manufacturers typically distribute premixed paints and stains in a small number of popular colors. To accommodate consumer desires and to enable matching of existing painted or stained surfaces, architectural paint and stain manufacturers typically also distribute a set of tintable base paints or stains and several concentrated colorants. These are combined at point-of-sale outlets using colorant dispensing and shaker mixing equipment to make small batch lots of custom-tinted paints or stains in a much larger array of colors than the limited colors available in premixed products.
A typical custom color paint system may employ several tintable base paints ranging for example from a nearly filled container of bright white base intended to accept at most a small quantity of colorant, to a less-filled container of unpigmented transparent or clear base intended to accept a much larger quantity of colorant. Base paints or stains may employ various binders (e.g., natural or synthetic resins), binder forms (e.g., solution polymers or latex polymers) and vehicles (e.g., solvent-base or waterborne versions), and may provide various dried surface finishes (e.g., matte, semi-gloss or gloss finishes). Some manufacturers also sell colored base paints (e.g. red, blue and yellow colored bases) which are intended to be combined with additional colorants when one coat hiding power is desired for strongly-tinted custom paint shades.
Colorants may for example be volumetrically metered from a multiple-colorant dispensing stations, with 12 paint colorants typically being employed in paint tinting colorant dispensing stations for the U.S. market, and more (e.g., 16 or 24 colorants) sometimes being employed in other markets. The dispensing station may for example include an individual dispensing canister for each colorant, and each dispensing canister may for example include a manually- or automatically-movable piston which forces a metered amount of colorant through a nozzle or other dispensing orifice and into a container of base paint or stain.
Owing to environmental and other concerns, modern-day paints and stains desirably are formulated as low volatile organic compound (low VOC) products. The same is true for the colorants used to tint low VOC base paints and stains. Unfortunately, many low VOC colorants tend to dry out in the dispensing station. Such drying may partially or completely plug the associated dispensing station orifices, may cause colorant to leak from or rupture connections inside the dispensing station, or may cause colorant to spray from the dispensing station orifices at a sufficiently oblique angle so that the colorant misses the base paint or stain container. Other consequences of such plugging may include inaccurate colorant dispensing and tinting, or a periodic need to disassemble and clean the dispensing station. Some colorant manufacturers have attempted to address these problems by adding higher than normal humectants levels to colorant formulations. However, doing so may cause or aggravate blocking, especially in tints prepared by adding large amounts of colorant to clear bases. Some colorant or dispensing station manufacturers have attempted to address tip plugging by providing removable caps for the dispensing station orifices. Unfortunately, users must remember to install the caps when the dispensing station will be left idle for a sufficiently long time that plugging may occur (e.g., when a paint store closes for the day) and remove the caps when use of the dispensing station resumes (e.g., when the paint store reopens the following day). Some point-of-sale outlets have instead purchased or converted to dispensing stations equipped with a cap that automatically moves away from the dispensing orifices when the dispensing station is in use. Doing so may however be expensive, and many uncapped or manually capped dispensing stations are still being used.