According to given conditions, including type of plastic, use of plastic products, and plastic molding process. Among them, uses of plastic products include light resistance and weather resistance, migration, hiding power, transparency, aging resistance, toxicity (heavy metals), food hygiene (FDA), acid and alkali resistance, solvent resistance, mechanical strength, and thermal properties , electrical performance, etc.
Setting items include colorant shape, color matching, colorant, selection (including addition amount, colorant variety selection), design formula, repeated color matching test, color matching completed, colorant variety selection including weather resistance, dispersibility, deformation, and filterability, migration, heat sealability, safety, coloring cost.

 

Type of plastic of sample;
Plastic use of sample;
Sample molding process.
According to above three conditions, we can understand requirements (heat resistance, light resistance, weather resistance, migration resistance, safety) that colorant selected for product needs to meet. In addition, color matching personnel also need to confirm dosage form of colorant required by customer (pigment dry powder, masterbatch, sand, modified material), and confirm coloring ratio (addition amount) required by customer.

Choice of pigments. Colorant is selected according to whether sample is transparent, opaque or translucent.　
Comprehensive consideration of coloring costs. Cost is also a very important consideration. Price of a pigment is as important as performance of pigment.
A preliminary formula is drawn up. After repeated research, difference between standard color sample and reference is repeatedly compared in terms of hue, brightness, intensity, etc., on this basis, colorant formula of reference material is revised, and a preliminary formula is drawn up. In the absence of a reference, color shade, hue and brightness of plastic product (sample) should be carefully analyzed to determine color attributes, then match colors according to Munsell color system, and draw up formula.

At present, plastic matching method adopted by various enterprises is actually a trial and error method, which is not very scientific, but it is still very recognized in color matching of plastics industry and is widely used by most enterprises.
Color matching personnel conduct actual coloring test according to preliminary formula, compare actual coloring sample with standard color sample and reference object, and further adjust coloring formula. Then prepare samples for comparison according to adjusted formula.

Color comparison between sample and sample provided by customer is a very important part of color matching. Sample comparisons are made according to customer's sample production process. Film products are often compared by blown film method, injection molded products are compared by injection molding method, and fiber products are compared by spinning method.

It is best to use natural light as the light source during visual inspection. If possible, you can use a standard light source box. Otherwise, comparing colors of two samples under certain lights may make colors look same due to phenomenon of "metamerism", but there is a larger color difference under natural light.

Products of different thicknesses have different feelings to human eye; smaller thicknesses are more transparent and lighter in color. Therefore, when matching colors, try to make thickness of sample and customer's sample as consistent as possible.

Different surfaces have different light reflections. For example, on same sample, color of a high-gloss surface into a matte surface obviously gives people different feelings. On same sample, rough surface is darker and darker than smooth surface, so color is compared. When observing, compare parts with similar surface conditions as much as possible.

Color of same pigment used in different resins is different. This is caused by difference in color and transparency of resin. Therefore, color should be matched with resin provided by customer as much as possible to ensure accuracy of color, especially modified material. More attention should be paid to color matching.

The most common problem in process of checking is colorimetric judgment error. Judgment error is mainly caused by insufficient experience. Usually it can only be solved by continuous practice and continuous enrichment of experience. Appropriate use of some instruments such as colorimeters can also help correct judgments.

A pair of samples are made of different colorants. When they are illuminated by a specific light source and viewed by a specific observer, colors match.
If once lighting changes, object will no longer match. Metamerism is very common and sometimes unpleasant, but metamerism can make many different pigment color combinations possible. Toxic colorants can be replaced with non-toxic colorants.
Expensive colorants can be replaced with cheap colorants to reduce costs. Due to existence of metamerism, it is possible to use different colorants to give a new formula. Color matchers can assign coordinates to a product in a color space to match their colors, even though they are made of different colorants. The only way to eliminate conditional color matching of objects is to use same colorant.