What Are the Differences Between a Thinner & a Reducer for Automotive Paint?

by Michael E Carpenter
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Thinners and reducers in automotive paints are both solvents used to thin paint. These additives make the paint flow better so the result is even, professional coats. While the purpose of the two is basically the same, thinners and reducers are used on very different paints. Using the wrong one could ruin your paint.

Paint Type

The main difference between thinners and reducers is in the paint type that is being applied. Thinners are for lacquer-based paints. Reducers are used for urethane-based paints. The two solvents are not interchangeable. For example, if the paint is an enamel-based product, do not use a thinner, but rather a reducer.

Manufacturer Instructions

Each brand of automotive paint will come with instructions on which solvent to use and what the mixing requirements are for the paint and solvent. It is very important that you follow the directions from the manufacturer exactly to get the best results. The paint will tell you explicitly whether a thinner or a reducer should be used to thin the paint.

Signs of Mismatched Solvents

Some symptoms that the solvent used was incorrectly matched to the paint include poor gloss and adhesion, dullness, chalking, cracks or splits, blisters, sanding swell, blushing or bleed-through of color. Color bleed is caused by solvents reacting with the undercoats, causing the undercoat color to show through the top finish. The fixes for each symptom are time-consuming and require you to use more paint to complete the job correctly.


Each paint manufacturer uses its own terminology when it comes to solvents. For example, some European companies refer to reducers as thinners, which can be very confusing. It is very important that the solvent selected matches with the manufacturer's recommendations for which solvents to use, including using the right proportions and taking into consideration various environmental situations, such as hot or humid weather. If you have any questions, contact the manufacturer directly to verify whether the solvent and paint selected will work together properly before applying it to your automobile.

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