Display Drawdown Charts and Spreading Rate Drawdown Charts Explained 3

When customers go to the store, they need to know how many gallons of paint to buy to cover the area they wish to paint.  They also want to know how many coats it takes to completely hide what they are painting over.  The spreading rate of a paint is how to determine how “far” a paint will go by quantifying how much area is covered for a given quantity of paint. Sometimes to compare paints, a researcher will use the same spreading rate for two different paints and then compare the hiding power visually using the background of the drawdown chart as a guide or instrumentally using a spectrophotometer.

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Penopac Drawdown Charts Explained 5

Paint produced by the architectural paint industry must perform on a wide range of substrates. Some examples are previously coated wallboard, from glossy to flat, wood trim, plaster, uncoated wallboard, stucco, etc.  The porosity of these substrates varies greatly, yet the paint must maintain the same color and gloss appearance no matter the substrate.

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Opacity Drawdown Charts Explained 8

When we evaluate paint, we ask, “how much paint must be applied to hide the substrate below it?” or “does this paint hide better than that paint?”  Opacity is a paint’s ability to prevent the transmission of light in order to hide the substrate below it.  Throughout the paint industry, the terms hiding, opacity and contrast ratio have frequently been used interchangeably.  Hiding is a general term used to describe all of these concepts, including hiding power. However, hiding power also takes into account the spreading rate of paint and will not be discussed here. (More information on hiding power can be found in ASTM D 2805.) More…