First you must identify the customer's expectations and determine the characteristics of the container and its contents.

The major customer criteria usually include printing in the desired colors, and achieving the "no label" look. The "no label" look creates an image that blends into the container. There appears to be no depth to the label. Direct screen printing, heat-transfer decoration, and in-mold labels by their nature create this look. Nine out of ten applications will seek this visual effect.

In many instances, customers will use PMS numbers to specify their colors. What buyers mean by this is that they want the label to match the PMS color of the container, and will approve the label colors when the label is viewed on the glass or plastic package.

Gloss levels, which can range from high gloss to flat, influence the perceived colors of the label. Contents of the container can also affect color, especially on clear, translucent and frosty-clear containers.

To have a high probability of gaining customer approval of your label on the first press effort, the label converter should have product-filled production or prototype containers as the quality standard.

There are eight combinations of containers/label face stocks that impact the label image. These combinations are:

1. Clear Clear

2. Clear Opaque

3. Opaque Clear

4. Opaque Opaque

5. Translucent Clear

6. Translucent Opaque

7. Matte Clear

8. Matte Opaque

Clear label on clear container: In this scenario, clarity of the face stock, adhesive wet-out characteristics, product color, glass of the container, inks and coating are all factors that influence the aesthetics. Most commonly used containers are glass, PET, PP and polycarbonate.

Opaque label on opaque container: Gloss level of the container, container color, face stock opacity, and gloss levels of inks and varnish need to be taken into account. Gloss levels of opaque containers vary widely. The most widely used opaque container are made of HDPE. The have a flat gloss. In contrast, PP has a high gloss.

Opaque label on translucent container: The majority of translucent containers are made of unpigmented HDPE. Milk jugs and drug bottles are representative of this label/container combination. Matching the gloss of the inks and varnish to the container is very important. When the contents of the package are dark in color, they can affect the color match on the container.

Clear label on matte container: These can be tricky applications because the matte finish may have been created by a light acid etch or application of a thin chemical coating. I have seen situations where an adhesive with excellent wet-out properties caused the area behind the label to become a clear window. In this situation the adhesive should have low wet-out properties.

These four scenarios give an idea of the factors that influence the production of acceptable labels. You will find a chart showing the factors that come into play on all eight of the container/label combinations.

The road map for successfully printing labels for glass and plastic containers calls for two things: a good understanding of the customer's approval criteria, and the availability of the correct container filled with the appropriate product. Without these tools, you are driving blindfolded toward your destination.

Skip Heintzelman

Consulting Technical Editor

704/366-5204