Quarterly Articles

Minimizing Color Processing Costs

By Paul Uphaus, Commercial Development Manager, Primex Plastics

“As I hurtled through space, one thought kept crossing my mind – every part of this rocket was supplied by the lowest bidder.”

~John Glenn

If this was the case, why were the results sufficient to guarantee a successful mission?  There are two main reasons: 1) though the customer was buying based on the “low bidder price”, they received the right final product and acceptable reliability through knowledgeable design and 2) more importantly, the specifications were communicated accurately. It is true that the price dictated the performance of the end product, but both the supplier and the customer understood the specifications and the limitations of the design.

The same principle holds true when it comes to obtaining sufficient information for a color match for Extrusion – thermoforming, or other thermoplastic processes.   Specifically, there can NEVER be too much information.  The more information that can be obtained during origination, regarding the end use including any regulatory requirements, the more accurate you will be in presenting a cost-effective and correctly-performing product.  This is a critical discussion point when asking customers for detailed end use information, as they want fast and accurate results.   In general, it is perceived that, the industry average for approvals and orders obtained after a custom color match is approximately 20-30%, as color approval is driven in some cases by customer preference or other subjective criteria.  It is imperative that we improve this factor beyond this ratio, by providing enough starting information to formulate efficiently for the end product use.  This will help assure customer satisfaction and growth in our industry.

Let’s look at the most fundamental pieces of information required. Of course, adequate information must be requested at the beginning of a project. This includes, but is not limited to, the following primary questions:

  • What is the end product and use?
  • What is the exact resin to be used in the match? (Including all layers such as cap and substrate.)
  • Requirements such as FDA, CONEG, NSF, light fastness and / or weather fastness
  • Expected life-time or service-life in the end application
  • Sheet gauge before and after forming (depth of draw)
  • What is the light source used to view the final color match?
    • Daylight D65, C
    • Incandescent light A
    • Florescent light F2, F11
  • Is this a visual match or will an instrument such as a spectrophotometer be used?
  • What is the target to be matched?
Pantone color chart for thermoforming

Pantone color chart

The best color target medium is an actual piece of plastic of the color that you want in the resin type to be used in the application.  This is not always possible, however, as targets are most often in the form of:

  • Painted metal parts
  • Cloth or printed paper
  • Pantone numbers (most common)
    • These should be considered as “concept colors” as it is most likely not possible to match that exact color in plastic.

When Pantone numbers are supplied they must have a letter (C, M, or U) after the number. It is not an option to match Red 185 since the C stands for “Coated” and the U stands for “Uncoated”. They can look completely different. Pantones are ink on paper and not all pigments used in ink can be used for plastics. The age (color fade due to storage) and print differences between editions causes many Pantone matches to be rejected.

When applicable, you should also discuss the limitations of fluorescents and high Chroma colors when used outdoors. The brighter the color, the less stable it can be. Make sure to review processing limitations such as extruding a co-ex custom color over black or another field of color. Also consider the possible addition of regrind and the resin stability at the desired thickness. Determine at what light source the color will be viewed. Is it Daylight D65, C cool white fluorescent,Incandescent Light A or Fluorescent Light F2-F11? Is it critical to understand if the end user will be making a visual approval or if they will be using a spectrophotometer? This is Standard spectrophotometer imagealso where the light source comes in. Most color spectrophotometers are set for the Daylight D65 or C scale. Some colors such as yellow are very susceptible to the light source and may give different results. If one person views it in Daylight while another views it in Fluorescent Lighting, a failure can occur. The way color is viewed is a subject in itself and will be covered in future articles.

Another important consideration is that some colors such as metallic, fluorescents, or many transparent colors, cannot accurately be measured on a spectrophotometer. Texture can also distort the readings so an override is often used to visually assess the sample. A trained color technician can be as good as or better than the computer in determining the acceptability of the match.

Let’s take a look at a real-world example. The customer is designing a part for an outdoor playground and they are ready to request pricing.

Upfront Discussion

HMWPE playground equipment image

Brightly Colored HMWPE Playground Equipment

What is the actual color target?  Are there multiple matching parts? Is it a Pantone, a part they currently make, a color chip, a customer defined printed target or a market idea? Is durability testing of concern or required?  Most

importantly, what is the service life or point at which they would replace parts due to defect or wear? UV performance equals higher costs. Discuss the limitations of Fluorescent and High Chroma colors, if applicable. The brighter the color, the less stability is exhibited.

Next, consider the internal processing limitations, e.g. is co-ex over black or field of color required? What is the effect of the addition of regrind into the substrate and the resin stability at the desired thickness?) Not only can these factors affect the quality of the color but they can drastically influence the cost structure.

Control the Standards

This is perhaps one of the most critical subjects in color matching and one that can cause a customer to lose faith in a supplier’s ability, especially with computer-controlled standards. It is imperative to store and record the date for future reference.  If or when there is a color problem, this is the first place to start the investigation.  Always ask what standard chip was stored and then verify that both parties have the same standard. Be sure not to use a lot-chip or a re-created chip, unless all parties have agreed and both have stored that new standard. Storage of the visual standard chips should be in controlled envelopes in cool dark cabinets and dated.  Be careful when cleaning handling standards. Do not use cleaners which may have optical brightener or bleaching chemicals.

With good information as the key to developing the right product, we can all participate in minimizing cost and color processing issues while maximizing results.