How do places like Home Depot or Lowe’s color match paint colors from a paint chip sanple?

Question

I just got this done today and the paint is identical to the color I’m repainting from previous tenants. How does this witchcraft work???

In: Chemistry

Answer 1

What we perceive as the color of an object is just the frequency (or wavelength) of light reflecting off of that material when it is received by our eyes. So to color match a paint, you can use a device called a spectrophotometer, which shines white light on a given sample and then measures the light that is returned from the sample. The measuring can be done in a lot of different ways, from using a simple camera with a computer program that uses brute force to match the colors to using machine learning algorithms to speed up the process to using more sophisticated measuring devices such as interferometers. Once you get that wavelength or frequency, a computer can then tell you what colors need to be mixed to match that wavelength. Again, this can be done through brute force algorithms, more tailored algorithms, machine learning algorithms, and so on.

Some of the issues that arise with these processes relate to aspects like the sheen/reflectivity of the paint, the heterogeneity of the sample, and how the sample changes in age vs. the chemical composition of the replacement paint. [This link provides a very good description for more detail. ](https://www.housebeautiful.com/shopping/home-gadgets/a225/technophobia-color-matching/) [This link is also pretty good with regard to the typical device itself. ](https://laboratoryinfo.com/spectrophotometer/)

As for the current state of the art, I would imagine that the more sophisticated commercial devices are using a variety of measuring tools along with highly tailored machine learning algorithms to look at aspects of the substrate material, density and porosity of the coating, reactions to environmental materials, and so on to make more efficient calculations and to handle all of the variations that may later come into play. That said, I’m only peripherally aware of this field so there may be other key aspects I’m missing.