As ambient temperatures rise during the warmer months, professional painters are faced with a distinct set of challenges that can significantly affect application processes, finish quality, and overall coating performance. Understanding the behaviour of different paint types under thermal stress is crucial for ensuring consistent results and avoiding costly rework whether this be in industrial or joinery sectors.
This guide from our Total Paint Shop Support team explores how elevated temperatures influence paint performance, identifies common issues that may arise, and offers practical recommendations - including product-specific guidance to help professionals maintain quality and efficiency throughout the summer season.
Key Differences by Paint Type
Not all coatings respond the same way to increased temperatures. The chemical composition of a paint system determines how it behaves during application and curing.
Water-Based Paints:
Water-based coatings generally tolerate elevated temperatures more effectively. While drying times are accelerated, they tend to remain more stable during application and are less prone to the volatility seen in solvent-based products. Their compatibility with modern spray booth systems makes them particularly well-suited to high-temperature environments such as our Aquimax paint range.
Solvent-Based Paints:
Solvent-based coatings become considerably more difficult to manage in warmer conditions. Increased evaporation rates lead to rapid surface drying, reducing working time and making it more difficult to achieve a uniform finish. The accelerated loss of volatile organic compounds (VOCs) can hinder film formation and gloss retention, resulting in dull, uneven coatings.
The Impact of High Temperatures on Coating Application
1. Drying Times
Elevated temperatures significantly accelerate drying times. While this can improve productivity, it also reduces open time - limiting your ability to achieve a smooth, consistent coverage. Fast drying may prevent the film from levelling out, impacting gloss and texture.
2. Adhesion and Substrate Interaction
When surfaces are overly warm, coatings may fail to properly bond, leading to reduced adhesion. This is particularly problematic for solvent-based systems.
3. Finish Quality and Wet Edge Maintenance
Maintaining a “wet edge” is essential when applying coatings to large surface areas. In hot conditions, paint can dry before the applicator completes, resulting in overlapping lines, inconsistent sheen, and a rough or patchy finish.
4. Product Workability
Higher temperatures reduce pot life of two-pack paints, requiring faster application and potentially leading to material waste if not properly managed.
Common Defects When Painting in High Temperatures
Blistering:
One of the most common issues in elevated temperatures, blistering occurs when a coating dries too rapidly - trapping air or solvents beneath the surface. This results in bubbles or raised areas, compromising both aesthetics and performance.
Flashing:
Gloss variations across the painted surface, or “flashing,” can occur when sections dry at differing rates. This is exacerbated when working in direct sunlight or in inconsistent airflow conditions.
Poor Flow and Surface Texture:
Rapid drying impairs the paint’s ability to level out, locking in brush marks or spray pattern textures. This leads to a rough, sandpaper-like finish, especially noticeable on high-gloss coatings.
Best Practices for Professionals Painting Warm Weather
Applying professional coatings in hot weather requires a strategic and informed approach. High ambient temperatures, heated substrates, and faster solvent or water evaporation can all negatively impact application, film formation, and final finish. The following best practices are designed to help professionals optimise paint performance, minimise defects, and achieve durable, consistent finishes in elevated temperatures.
1. Select Heat-Tolerant Paint Systems
Product formulation matters. Choose coatings that are specifically designed or proven to perform well under higher temperatures. In particular, water-based coatings are generally more stable in heat compared to solvent-based systems.
- Water-based benefits in warm conditions: Slower evaporation of water compared to solvents means better flow and reduced flashing.
- Ultrimax Recommendation: The Aquimax and Sayerlack water based range offers excellent temperature stability and dries effectively through airflow rather than relying on high heat, making it ideal for warm-weather application.
2. Avoid Use of Thinners in Solvent-Based Coatings
While adding thinners to solvent-based paints may seem like a solution to extend working time, it often leads to over-thinning, increased volatility, and poor film integrity. Thinners can exacerbate premature drying, increase VOC emissions, and create unpredictable flow patterns, particularly in high heat.
Best practice:
- Use solvent-based coatings at the manufacturer’s recommended viscosity. If adjustments are needed, consult the technical datasheet.
- Consider switching to low-VOC or water-based alternatives during summer months for easier control.
3. Optimise Spray Booth Conditions
If you’re working within a spray booth, environmental control becomes your greatest asset. In warmer months, avoid using bake cycles unless required for curing. Instead, focus on airflow and ventilation to promote uniform drying without forcing solvent or water out of the film too quickly.
Warm-weather booth configuration:
- Disable bake mode
- Increase airflow/fan circulation to maintain air exchange
- Ensure filters are clean and operational to avoid contamination
- Ultrimax Recommendation: Use Aquimax in booths with strong air circulation for consistent, defect-free drying.
4. Time Your Application Strategically
Application time can dramatically impact finish quality. Coating in the peak of the day, particularly in unshaded areas, can result in substrates heating above the air temperature, speeding up drying beyond workable levels.
Ideal application windows:
- Early morning or late afternoon
- When surfaces are cooler than 30°C
- Tip: Use an infrared thermometer to monitor substrate temperature. Surface temp should ideally be at least 3°C above the dew point but below 35°C to avoid flash drying and poor adhesion.
5. Maintain a Wet Edge on Large Surfaces
Hot weather makes it difficult to keep a wet edge, especially when coating expansive areas such as tanks, industrial panels, or large metal areas. Rapid drying prevents the paint from levelling properly, causing lap marks, flashing, or visible seams.
Solution:
- Break large areas into manageable sections.
- Use spray application techniques that provide even, consistent coverage.
- Have additional personnel on hand for back-rolling or blending in critical areas.
- Consider using retarders (if approved by the manufacturer) to extend working time in specific situations.
6. Adjust Application Techniques and Equipment
In warmer temperatures, atomisation and spray pattern control become more critical due to faster solvent or water evaporation mid-air. You may need to adjust equipment settings to achieve the desired finish.
Spray gun settings:
- Reduce atomising pressure slightly to slow down evaporation.
- Use a larger nozzle size if the product begins to dry too fast through a finer tip.
- Consider air-assisted or airless spray systems to increase coverage speed and reduce dwell time between passes.
7. Store Materials Correctly
Storage conditions for paints and hardeners are crucial in maintaining product stability.
- Keep paints out of direct sunlight. Ideal storage temperature is typically 10/25°C
- Avoid leaving paint cans or equipment in vehicles or exposed warehouses where temperatures can exceed 40°C
- Always mix and condition products in a shaded or temperature-controlled environment before application
8. Use Proper Personal Protective Equipment (PPE)
Working in hot conditions increases fatigue and the risk of heat stress. Choosing the right PPE helps maintain safety without compromising comfort.
- Ultrimax breathable spray overalls are designed specifically for industrial painters working in warm environments. They provide full-body protection while promoting airflow to reduce overheating.
- Stay hydrated, and implement regular breaks during longer coating sessions in high heat.
Warmer weather doesn’t need to compromise coating quality. With a clear understanding of how temperature impacts paint behaviour, and by leveraging suitable products and equipment, you can maintain high standards of finish, efficiency, and durability throughout the summer months.
For tailored advice or support in selecting the right coating system for your facility, contact our Total Paint Shop Support team today.