Lot-to-Lot Color Match
Color ControlEach PPS color match follows this process:
1. Request – The customer requests a match to a specific color, and provides PPS with one of the following:
• A color swatch
• A PMS color number
• A number from another color system such as American Standards, Munsell, etc.
This request also specifies to PPS the requirements of the match:
• Precise color match – within +/- one delta E, or
• Commercial match – within 4 delta E
2. Sample – The sample is read on our color photospectrometer, which formulates the analyzed color. The ink is then mixed according to the computer's instructions.
When color matching to a PMS number, we use our PMS data bank program for the formula and to make a color comparison after the batch of ink is mixed. (Using the data bank instead of a PMS book is essential because PMS books vary as high as three delta E.)
3. Swatches – Eight color swatches are made using the computer generated formula:
• PPS sends four swatches to you for color approval.
• Upon approval, these become the master color-control swatches for engineering and quality control.
• PPS retains four swatches as our master color-control swatches for your color.
4. New Lots – Each time another lot is printed, the color is compared to the computer data and checked visually to the master color-control swatch. The process includes:
• Swatches for jobs to be printed on a second surface will be color matched on the second surface of the substrate.
• For texturized parts, color swatches will be texturized.
At PPS we use the accurate computer photospectrometer to formulate, compare and store all color information. This gives us the ability to furnish consistent color from run to run – unaffected by differences in how humans see colors.
Note: Since not everyone has this technology, we have also included the usual method of visually checking colors in the "Criteria for Viewing Colors" section below.
In case of disagreement about the accuracy of a color match, computer results will be considered the determining factor.
5. Control Criteria
• Establish a control – Always establish control color swatches, printed on the appropriate surface of the substrate to be used to produce your part. (A color printed on a second surface using a different substrate requires another color match.)
• Check against original – Always compare current lots of parts to the original control color swatch for color verification. (Comparing lot to lot will ultimately result in color drift.)
• Control the light source – Always use a consistent light source to view colors while taking care to prevent ambient color influences. (Specify on your print how you want parts viewed: light source, candle power and viewing method.)
Criteria for Viewing Colors
PPS designed its system for viewing colors without spectral interference.
Following is the most accurate system that can be used for visually comparing a newly formulated color match to the original color sample:
• Eliminating all extraneous color, which can distort color perception.
• Using a Munsel N-8 neutral gray mask with two 3/8" holes, 1/2" apart, over the original and the PPS prepared swatches.
• Unless otherwise specified, comparing all colors per American National Standards Institute PH2.45 1979.
• Using a Macbeth color viewing booth with 5000 Kelvin illuminent.
• The person viewing the color will have 20/20 or corrected to 20/20 vision and have unimpaired color perception. Any glasses worn will not contain any tint and will not be optic gray.
Note: All measurements are in inches.
Transparent Color Control:
• Viewing transparent colors using the same N-8 gray viewing mask. If feasible, viewing will be performed over your actual light source.
• Using the same substrate the parts will be manufactured on when the transparent color is to be printed on a second surface.
• Viewing textured parts through the texture.
Ink Opacity Control:
• When opacity is required, checking non-backlit parts by underlaying them with 1/4" grid pattern of .050 black lines printed on white. No pattern (grid) will be discernible through ink in required opaque areas, with overlay and grid patttern stationary.
• When portions need to be opaque, underlaying backlit parts with a black grid pattern of .050 black lines printed on clear material and placing them between printed piece and illuminent. No pattern (grid) will be visible in specified opaque areas.
For questions or clarifications call PPS at 913-791-9595 or toll free at 800-466-0626.
