Paint is defined as a mixture of various materials. The question is how much of which material, and how these things are related. These materials fall into four broad categories: resins, pigments, solvents, and additives.
resin
These are usually solid, sticky materials that hold the system together. They are also known as binders, and when in solvent, they are the vehicle of the system. They may be "single pack" or "two pack" systems. Single packs are just liquid resin or solvent resin. Two packs means that part "A" is mixed with part "B" to create a chemical reaction. In both systems, we need to know the solid resin content. This dry matter divided by the total dry matter plus solvent is often referred to as "resin solids". For a dual-encapsulation system, we need to know not only the solid, but also the proportion of the solid that forms the desired film. This ratio can be specified as a simple ratio of 1 to 1. Or it can be based on 1 or 100, i.e. 0.3 to 1, or 30 parts per 100, or 100 in total, i.e. 43 to 57. These ratios determine the properties of the film. We also need to know the density (weight per unit volume, usually lbs/gallon) of the resin or vehicle to help calculate volume.
paint
Pigments are dry materials added to coatings to impart color or resistance properties, camouflage properties, etc. to the coating. Pigments can be divided into many different categories according to different uses. Some materials are primary pigments rather than extender pigments. Some materials are organic in nature while others are inorganic. Properties such as light fastness, particle size and specific color are reasons for selection. For calculation purposes, each pigment requires a dry density and evaporated mass.
solvent
The material that keeps the coating in its liquid state is called a solvent. Solvents may be organic; they may even be water. Their formulations aid in the mixing, viscosity and application of paints. After application, they evaporate, leaving behind a dry film. For calculation purposes, the density needs to be known.
additive
These ingredients are added in small amounts (<5%) to alter certain properties of the coating. They need to be included in the calculations as they take solids and density into account.
We study the relationship between various components in terms of weight and volume. Each aspect not only states the relationship, but also implies certain properties of the formula. Experienced formulators can use many relationships interchangeably because they have a deep understanding of the process. It was common practice many years ago to produce paint in batches of 100 gallons. The ingredients are called "pounds per 100 gallons". However, if the batch is not 100 gallons, then the ingredients are said to be "pounds per gallon". So statements like "it already has 100 lbs of pigment" and "well, let's increase it to 2 lbs" make sense when you understand the practice of swapping base numbers. The density (weight per unit volume) of a material is usually expressed in pounds per gallon. To convert a number to a volumetric measurement (volume per unit weight), or "volume factor," divide the density by 1. Coefficient of Expansion = 1/(Density in lbs/gallon)
