Selection of pigments for paints.

Choosing the proper pigment depends on the purpose of the paint to be formulated. In some cases it will control the coloring and the opacity of the paint film, characteristics required for house paints, for example. In other cases it will manage other properties of the formulation in question, such as, the anti-corrosion capacity, for example. 

Once the possibilities of the media to be used are defined, the step is the choice of the pigment, which will depend first on the color the customer wants to obtain.

For a proper choice of primary pigments, it is necessary to consider some rules regarding the main properties: resistance to bad weather, dyeing power, resistance to light, coverage power and dispersion.    

1. Resistance to bad weather conditions
When choosing a pigment with high resistance to bad weather conditions, you must consider a vehicle with compatible resistance.

2. Dyeing power
The vehicle interferes in the pigments’ dyeing power, therefore it is necessary to perform tests to assess the pigment’s dyeing power in the different vehicle. When there are several pigments for the same color, for cost reasons, it is better to choose the ones with higher dyeing power. 

3. Resistance to light
It is important to assess the pigments’ resistance to light, for mixing elements with a big difference in this regard jeopardizes the final color or potential repainting. 

4. Coating power
The pigments should be worked with in an optimal way or below the ideal PVCs to prevent loss of coating.  

5. Dispersion
It is important to produce experimental lots to obtain the formulation’s balance, trying to define the most suitable vehicle for the dispersion and the use of proper equipment for production; you must remember that optimizing dispersion generates productivity and savings.   

(Text based on the book "Tintas e vernizes - Ciência e tecnologia" by ABRAFATI – 2nd edition - p. 532 e 536).