How Paint Is Made And Where Waste Arises

Most paints are built from four constituent groups. Pigments provide colour and hiding power, and they can be mineral, synthetic or metallic depending on the product. Binders, also called resins, form the film that remains once the paint has dried and hold the pigment to the surface. A carrier, either water or organic solvent, keeps the mixture fluid enough to apply and then leaves the film as it dries. Additives are added in small amounts to control properties such as flow, drying speed, skinning resistance or microbial growth.

The FIVA guide to paint raw materials sets out these constituent groups and the role each one plays in a finished coating, and the KFUPM course chapter on paints, pigments and industrial coatings covers the same groups from a formulation perspective, including how pigment and binder choice affects performance.

Production generally follows a sequence, though the detail varies by product type and by manufacturer. Raw materials (pigments, resins, solvents or water, and additives) arrive and are checked in. Pigments are first wetted out and pre-dispersed in part of the binder and carrier to break up clumps. The mixture then goes through milling or grinding equipment to reduce particle size and disperse the pigment evenly.

Once the base is ground to the required fineness, it is let down: diluted with the remaining binder, carrier and additives to the final formulation, and adjusted to match viscosity, colour and other specification targets. Tinting adds colourants to reach a specific shade. The finished batch is then filled into tins, drums or other packaging, labelled and put into stock. Equipment is cleaned between batches, particularly between different colours or product types, to avoid contaminating the next run.

Waste can be created at almost every stage of that sequence. The table below sets out common waste-generating points against the process stage they belong to.

In addition to these in-process points, waste also arises after a product has reached the market: returned goods that customers send back, obsolete stock that is discontinued or has passed its shelf life, and filter or screen residues removed during routine maintenance of mixing and filling equipment.

Not every batch passes quality control first time. A batch can fail on colour match, viscosity, fineness of grind or another specification parameter. Where the fault can be corrected, by further tinting or adjustment for example, the batch may be reworked back into production. Where it cannot be corrected economically, it becomes waste.

• Batches rejected for colour, viscosity or other specification failures
• Flush material generated when lines are changed from one product or colour to another
• Filter and screen residues collected during routine maintenance
• Spilled or damaged packaging that cannot be resold
• Returned goods from customers
• Obsolete or discontinued stock

A producer who can describe the batch in front of them gets through an enquiry faster, whether it is a one-off clearance or a recurring collection built around a production schedule.

Knowing where a waste came from in the production process is useful context, but it is not a substitute for classifying it. The Environment Agency's waste classification technical guidance (WM3) sets out the process for assigning the correct waste classification based on composition and hazard, and GOV.UK's guidance on hazardous waste explains the duties that fall on producers and holders of hazardous waste once a material has been classified as such.

If the waste you are dealing with is leftover or surplus product from a production run, surplus paint disposal covers that route. Where the waste is sludge from mixing, filtration or tank cleaning, paint sludge disposal is the more relevant starting point.