As temperatures rise, automotive refinishing becomes more challenging. High heat can impact everything from product performance to application results. To help refinishers maintain top-quality results through the summer months, Sherwin-Williams has compiled some essential tips and practices to keep your finishes flawless and your shop efficient, even in the hottest conditions.

1. Choose the right hardener and thinner

One of the most critical steps in summer refinishing is selecting the correct hardener and thinner based on ambient temperature. Slow hardeners and thinners are specifically formulated for higher temperatures, allowing for proper flow and levelling without rushing the cure process.

However, consistency is key. If you opt for a slower hardener, always pair it with the matching thinner. Mixing mismatched components can lead to gloss retention issues or undesirable surface imperfections. Be sure to consult the product’s Technical Data Sheet (TDS) for the recommended combinations if you’re unsure.

2. Minimize thinner use in clear coats

When working with clear coats in high heat, it’s best to use the minimum amount of thinner permitted by the mixing ratio. Excessive thinner, especially in hot conditions, can cause the clear coat to dry too quickly, leading to dry spray or poor flow. Staying within the lower range of the TDS-specified ratio helps to maintain better control and finish quality.

3. Avoid direct sunlight on products

Never store paint products, thinners, or hardeners in direct sunlight. Exposure to heat and UV rays can change a product’s viscosity and chemical balance, affecting its performance. Always keep materials in a cool, shaded storage area, ideally within the temperature range specified by the manufacturer.

Also, remember to always replace the lid on hardeners as soon as possible after pouring. Exposure to air, even briefly, can cause chemical breakdowns, reducing the product’s effectiveness and pot life.

4. Cool down the spray booth between jobs

Spray booth temperatures can rise significantly after each job, especially during back-to-back work in the summer. Cooling down the booth between cycles is essential to avoid carry-over heat affecting the next application. Overheated panels can make it difficult for the paint to stay wet, leading to uneven finishes or dry spray.

5. Use a larger nozzle at high temperatures

In hotter environments, switching to the largest nozzle setup recommended in the TDS can make a noticeable difference. A larger nozzle allows for greater material output, which helps the paint remain wet on the surface and improves coverage. This is especially important for basecoats and clear coats where a consistent, wet film is crucial.

6. Use an anti-static cleaner for final wipes

Summer heat often comes with dry, dusty conditions. Static charges on panels can attract fine dirt and debris, compromising the finish. Using an anti-static cleaner as a final wipe reduces the attraction of dust and results in a cleaner, more professional outcome. It’s a simple step that makes a big impact, especially on high-visibility panel

7. Mix per layer for larger repairs

For larger repairs in high temperatures, we recommend mixing product per layer rather than preparing a full batch. Heat accelerates curing, shortening pot life and changing viscosity mid-application. By mixing fresh product for each coat, you maintain the correct consistency and avoid issues like clumping, uneven coverage, or product waste.

8. Spray during the cooler parts of the day

Timing is everything in summer refinishing. Schedule painting for the early morning or late afternoon to avoid the peak heat of the day. Cooler conditions help maintain better control of viscosity, spray pattern, and drying times. Not only does this improve finish quality, but it also reduces stress on your team and equipment.

You could also coordinate your shop workflow to prioritize prep and non-paint activities during midday hours and reserve your spray booth time for when conditions are most favorable.

Summer refinishing doesn’t have to mean compromised quality. By adjusting your materials, workflow, and application techniques, you can still maintain excellent results. Sherwin-Williams offers a full range of temperature-appropriate products and expert support to help you keep every job running smoothly, no matter the season.