Measuring Translucent and Opaque Bottles Using the LabScan XE

The final color of plastic and glass bottles is often measured to ensure lot-to-lot consistency. Bottles that are translucent or opaque may be measured in reflectance, specular included (RSIN) mode using a benchtop instrument such as the LabScan XE.

A HunterLab LabScan XE 0/45 spectrophotometer can be used to measure the reflectance of translucent and opaque bottles. The sample clamp option may be used to hold single-wall bottle cut-outs at the sample port. This is the method advocated by HunterLab for the measurement of translucent and opaque bottles of various sizes. It is also possible to measure the color of whole finished bottles, using the optional sample clamp to hold the bottle at the reflectance port, however the measurement is less precise than with the bottle cut-out method.

The LabScan XE

The Application

Bottles have several non-uniform characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.

The samples are rounded, and so consistent placement using a special handling device is required in order to make the samples appear as flat as possible to the instrument.
The samples may be translucent and will look different when backed with different backgrounds. Using a special handling device that provides a constant background will minimize this effect.

Recommended Color Scale	CIE Lab* as a full color descriptor
Recommended Single-Number Indices	YI D1925 (2/C), YI E313, WI E313 when samples are near white
Recommended Illuminant/Observer	D65/10°.

Measurement Methods

Method #1: Measuring Bottle Cut-outs. This method is preferred as the most repeatable and reproducible method of measuring translucent and opaque bottles.

1. Configure your software to read using the desired color scale, illuminant, and observer.
2. Place the instrument in the port-up orientation and install the sample clamp (HunterLab Part Number D02-1009-200) over the sample port. Ensure that the white disk (rather than the black, non-skid disk) is installed on the sample clamp. This will provide a constant white background for the cut-out.
3. Standardize the instrument for the 1.75 inch (largest) area of view. First standardize on the black glass, then on the white tile.
4. Cut out a segment of the bottle sample that is at least two inches square. This area should be as flat and smooth as possible with no labels, markings, or embossed areas.
5. Cover the sample port with the cut-out and hold it in place using the sample clamp.
6. Measure the cut-out.
7. Rotate the cut-out 90° and take a second reading.
8. Average the two color readings for a single measurement representing its color. Averaging multiple readings with rotation between readings minimizes measurement variation associated with directionality, texture, and non-uniform color.
9. Record the average color values.

Method #2: Measuring Whole Bottles. This method should be used only when time constraints or other factors prohibit measuring bottle cut-outs.

1. Configure your software to read using the desired color scale, illuminant, and observer.
2. Place the instrument in the port-up orientation and install the sample clamp (HunterLab Part Number D02-1009-200) over the sample port. Ensure that the white disk (rather than the black, non-skid disk) is installed on the sample clamp. This will provide a constant white background for the bottle.
3. Standardize the instrument for the 1.75 inch (largest) area of view. First standardize on the black glass, then on the white tile.
4. Locate a flat area on the bottle free of any labels, markings, or embossed areas and cover the sample port with this area of bottle. Hold the bottle in place using the sample clamp.
5. Measure the bottle.
6. Turn the bottle over and measure it again (in a flat area free of labels, markings, or embossed areas).
7. Average the two or more color readings for a single measurement representing its color. Averaging multiple readings with rotation between readings minimizes measurement variation associated with directionality, texture, and non-uniform color.
8. Record the average color values.