The paint and coatings industry makes frequent use of these measurements. Then, the spectro-guide automatically displays the Opacity (%). Push the STD button while the spectro-guide in on the black and then the Operate button while on the white. Simply select “Opacity” in the Option-Index pull down menu while in Difference Mode. With a BYK-Gardner spectro-guide, you can skip this calculation completely and let the spectro-guide do the work for you. Therefore, no differences can be seen on the drawdown between black or white for a 100% opacity measurement. Opacity (%) is simply the Contrast Ratio multiplied by 100 to get a percentage, where 100% is complete hiding.
Then calculate the contrast ratio and/or opacity as shown below.Ĭontrast Ratio is defined in ASTM D 2805 as the ratio of the reflectance (Y-tristimulus value) of a film on a black surface to that of an identical film on a white substrate. On the second or third day (or your own specified time limit), use a spectrophotometer like the spectro-guide to measure the Y-tristimulus value for the coating over black and for over white on all your drawdowns.
Each drawdown should be placed horizontally in a well-ventilated area to dry. Hold the charts flat with a vacuum pate or another suitable device. Using a byko-chart Opacity Drawdown Chart, make a drawdown manually at the rate of 6cm/s according to ASTM D 2805. BYK-Gardner byko-chart’s white and black areas have the tightest tolerances in the industry ensuring repeatable measurement batch after batch. Opacity charts are used to make measurements for calculating Percent Opacity and the Contrast Ratio. Opacity drawdown charts are made up of white and black areas that are large enough to make a reflectivity measurement with a spectrophotometer such as the BYK-Gardner spectro-guide. (More information on hiding power can be found in ASTM D 2805.) However, hiding power also takes into account the spreading rate of paint and will not be discussed here. Hiding is a general term used to describe all of these concepts, including hiding power. Throughout the paint industry, the terms hiding, opacity and contrast ratio have frequently been used interchangeably.
For example, we mark 1.0mm wire diameter as 100 um wire-wound rod, 100 um is only theoretical wet film thickness, and the achieved fact wet film thickness is only 75%～80% of theoretical value.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. Note: All rods produced by Biuged are distinguished by its wire diameter or groove depeth. ◆ Simultaneous drawdown of several samples side by side is possible ◆ Maximum attainable wet film thickness engraved on bar end ◆ Ideal for flexible materials such as paper, cardboard, test charts, foils, leather, textiles, etc. ◆ Bar and wire manufactured of stainless steel These applicators provide an economical way to assure the uniformity of thickness of very thin films. The motion of the drawdown is done by gripping the 2 edges of the applicator or by using the Holder Black/White Test Chart, Glass or Wood Panel, etc.）onto our Drawdown Board. A coating（Paint or Ink）is being drawdown by a known thickness wire-rod applicator over a substrate（eg. The wire and its rod from the wire-wound rods are made of stainless steel，which are corrosion-resistance.
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