Color by the numbers: adding color management to a producer's quality control program

Concrete Producer, The, July, 2004 by Rick Yelton

Matching colors in concrete can be rough even for the best plant operators. Process improvements like powerful computer batching controls, accurate dispensing units, and high-quality coloring agents have aided producers in tightening coloring differences. But as each quality control manager knows, the architect and building owner still can find differences.

But getting the color right is becoming easier, as producers are employing measurement technology systems to help determine a unit's amount of color. New to the concrete industry, these devices have been effective in other industries as color management tools in quality control programs.

Several concrete block producers have already incorporated these optical measuring tools into their production processes, says Hal Good, an engineer at HunterLab Associates, a Reston, Va., manufacturer of color measurement systems.

The result has been not only better quality in the color of their final product, but reduced production costs and waste.

Meeting final specs

Installed in the process line, these color assessment devices help producers improve production quality. This approach is particularly effective when the instrumentation is used to measure the difference in color between a sample and a standard.

Producers should consider using color assessment in their production processes in four ways, says Good. First, they can monitor how an ingredient's hue can affect a unit's final color. They can determine color change resulting from curing or storage. They can use assessment devices to measure and ensure consistency of ingredient colors. Finally, they can even use these devices to determine conformity to final product specifications.

Good's company offers several devices producers can use in the plant to tighten pigment volumes in established recipes based on cement/pigment volumetric ratios, or even water/cement ratios. These meters, which cost about $3000, are mounted in locations to measure aggregate, sand, and cement color as they enter the batcher. Using a simple software program, operators can adjust the pigment levels to achieve a desired final hue.

Good has noticed another use of color assessment devices in the concrete production industry. "One or two operations use the devices to alert the plant of whether the sand is wet or dry," he says. The devices can detect whether limestone sand is a little darker than normal. The plant operator then can increase the pigment or cement to lighten the color.

The science of color

The science behind color assessment is simple. HunterLab engineers use a proprietary coloring scale to create a value for a color. Their system is based on the concept that the human eye doesn't see red and green, nor yellow and blue, at the same time. So the human eye actually stores a color as a mathematical relationship of red to green, and of yellow to blue.

Like the eye, color assessment instruments can determine whether the sample is lighter in color than the standard, is more red (or less green), or more yellow (or less blue). And since each color combination is a mathematical relationship, a technician can determine how much pigment of a known color should be added to bring the input back to a standard.

Another advantage of this by-the-numbers approach is it provides an unbiased scale to solve perception differences in eyeballing color. Some producers have used hand-held color assessment tools to prove to architects that the color meets the specs. "It's an easy way to settle a jobsite dispute when the reading indicates a block or paver is within the range of the standard," says Good.

For more information on HunterLab Associates' wide range of color measurement instruments, visit www.hunterlab.com, telephone 703-471-6870, or Circle 3 on the reader service card.

The table lists companies that provide integral colors to producers.
The pigments come in the form of metallic oxides, from either natural
or synthetic sources. Many of the providers yield colors from a
standard group of oxides. Iron is by far the most common, and is used
to yield black, red, and yellow. Blend them to get the browns,
siennas, and a variety of other earth tones. Chromium yields a green
color, while cobalt is for blue; titanium dioxide imparts a white
color.

The form in which these pigments are sold does change from company to
company. Use the table to match your need--whether granular, liquid,
or powdered integral colors or color hardeners--with the color
supplier who sells it.

                               Integral Colors

Company                   Granular   Liquid   Powder   Color Hardeners

Alabama Pigments Co          0         X        X             0
Bayer Chemicals Corp         X         0        X             0
Butterfield Color            0         0        X             X
Cathay Pigments (USA)        0         0        X             0
  Inc
ChemSystems Inc              0         0        X             0
Concrete Solutions Inc       X         0        X             0
Davis Colors                 X         X        X             X
Dynamic Color Solutions      0         X        X             X
  Inc
Elementis Pigments Inc       X         X        X             0
Hoover Color Corp            X         0        X             0
Increte Systems Inc          X         X        X             X
Interstar Pigments,          X         X        X             0
  Admixtures & Fibers
L. M. Scofield Co            X         X        X             X
Master Builders Inc          0         X        0             0
New Riverside Ochre Co       0         0        X             0
Prism Pigments               0         0        X             X
Solomon Colors               0         X        X             0
Shepherd Colors Co           0         0        X             0
Specialty Concrete           X         0        X             0
  Products
Super Stone Inc              0         X        X             X

Company                   Oxides                   Phone

Alabama Pigments Co       Fe                       800-531-1172
Bayer Chemicals Corp      Fe, Zn, Cr               800-662-2927
Butterfield Color         Fe, Cr, Co, Ti           800-282-3388
Cathay Pigments (USA)     Fe                       800-576-1500
  Inc
ChemSystems Inc           Fe, Cr, Co, Ti           800-545-9827
Concrete Solutions Inc    Fe                       800-232-8311
Davis Colors              Fe, Cr, Ti, Carbon Blk   800-356-4848
Dynamic Color Solutions   Fe, Cr, Co, Ti           800-657-0737
  Inc
Elementis Pigments Inc    Fe, Cr, Co, Ti           800-323-7796
Hoover Color Corp         Fe, Cr, Co, Zn, Ni,      540-980-7233
                            Carbon Blk
Increte Systems Inc       Fe                       800-752-4626
Interstar Pigments,       Fe, Cr, Co, Ti           819-563-9975
  Admixtures & Fibers
L. M. Scofield Co         Fe                       800-800-9900
Master Builders Inc       Fe                       800-628-9990
New Riverside Ochre Co    Fe                       800-248-0176
Prism Pigments            Fe, Cr                   651-488-4250
Solomon Colors            Fe                       800-624-0261
Shepherd Colors Co        Fe, Co                   513-874-0714
Specialty Concrete        Fe, Cr, Co, Ti           800-533-4702
  Products
Super Stone Inc           Fe                       800-456-3561

                                                          Circle
                                                          Reader
Company                   Web site                        Service

Alabama Pigments Co       www.alabamapigments.com            4
Bayer Chemicals Corp      www.bayerus.com                    5
Butterfield Color         www.butterfieldcolor.com           6
Cathay Pigments (USA)     www.cathaypigments.com             7
  Inc
ChemSystems Inc           (no web)                           8
Concrete Solutions Inc    www.concretesolutions.com          9
Davis Colors              www.daviscolors.com                10
Dynamic Color Solutions   www.dynamiccolorsolutions.com      11
  Inc
Elementis Pigments Inc    www.elementispigments.com          12
Hoover Color Corp         www.hoovercolor.com                13
Increte Systems Inc       www.increte.com                    14
Interstar Pigments,       www.interstar.ca                   15
  Admixtures & Fibers
L. M. Scofield Co         www.scofield.com                   16
Master Builders Inc       www.masterbuilders.com             17
New Riverside Ochre Co    www.nroonline.com                  18
Prism Pigments            www.prismpigments.com              19
Solomon Colors            www.solomoncolors.com              20
Shepherd Colors Co        www.shepherdcolor.com              21
Specialty Concrete        www.scpusa.com                     22
  Products
Super Stone Inc           www.superstone.com                 23