Chapter 1: Adverse Environmental Conditions
As a member of a Factory Built Housing team, you enjoy an advantage. Your work is performed in a protected, secure, indoor environment where, for the most part, conditions can be controlled. Weather is seldom a factor though, in the factory, it can sometimes be a challenge to fully control the greatest impediments to quality paint – temperature and humidity.
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Temperature and Humidity
Temperature and humidity can have a significant impact not only on material drying and curing, but also on the general application and touch-up performance of primers and paints.
For proper paint application you must monitor and regulate:
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Materials Surface Temperature
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Ambient Air Temperature
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Product Storage Temperature
Temperature fluctuation may affect the degree of coalescence (film formation) of paint. Fluctuations can cause color variations even when material is sourced from the same container.
To ensure color and consistency match, touch-up paint should be applied in the same conditions that existed when the paint was first applied to the substrate.
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Storage
Ideally, latex paint materials should be stored and applied in ambient air temperatures about 50°F (10°C) and below 80° F (27°C), with a relative humidity of 50% or lower. Stacking of 5 gallon buckets should not exceed 3 buckets high.
Other materials, such as substrates, wallboard, siding, etc., should be stored according to manufacturers’ instructions, away from moisture and extreme temperatures. Containers should be sealed to prevent contamination and degradation.
Proper storage can dramatically reduce prep time for materials. When materials are moisture-free and within the recommended temperature range, they are ready for paint application.
Because of their tendency to absorb moisture, gypsum products should be stored in a dry environment.
Exterior siding and trim materials specified for painting should be stored in dry environments. Surfaces exposed to rain, fog, or high humidity conditions should be allowed to dry thoroughly and to reach the optimum temperature range prior to painting.
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Low Temperatures
The consistency of paint material is affected by temperature. At 50°F (10°C) or colder, paint material thickens, making it difficult to brush, roll, or spray properly. Applying paint to extremely cold surfaces may affect how well the material “hangs” and adheres to the substrate.
For low temperature application, exterior products have been formulated to cure at temperatures as low as 35°F (1.6°C). Compared to conventional exterior products, these products offer faster curing schedules and improved early moisture resistance. While these products can cure at lower temperatures, it is important to note that the rate of drying slows as temperature drops and relative humidity increases.
Exposure to temperatures outside of the recommended temperature range at any time during the process may affect curing and system integrity.
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High Temperatures
Without proper ventilation, condensation may occur on materials that have been stored in cooler areas than the environment in which paint is applied. Abrupt temperature shifts may cause uneven paint application as the materials warm up. This is often the case when materials are transported from cold storage into forced heat painting areas.
Dramatic temperature shifts may also cause mud cracking of paint, mudded seams, and cracking of applied texture materials.
At temperatures of 85°F (29°C) or higher, paint material thins, creating application problems. Applying paint to extremely hot surfaces may cause paint to dry too rapidly, often causing uneven painted surfaces.
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Ventilation
Ventilation is a critical component of the painting process. Proper air movement helps to remove moisture (condensation) on stored materials, and equally important, helps to reduce relative air humidity during the curing process of water-based materials.
- As an example, 10 gallons of paint (50% solids by volume) releases 5 gallons of solvent or water into the air, adding to the relative humidity in an enclosed environment. For proper drying to occur, 5 gallons of solve or water must evaporate out of the wet film. Without proper ventilation, this becomes a problem.
- In an environment at or near 100% relative humidity (air saturation) water will not evaporate, which means waterborne materials, such as paint, will not dry. Relative humidity is affected by temperature. Warmer air can “hold” much more moisture than can cooler air, and so saturation points will be reached much more quickly in cooler environments.
- Through the use of ventilation – fans, blowers, air movers – moist air can be exhausted. Dehumidifiers and space heaters may help accelerate the process. Air movement should be controlled and excessive air movement avoided, to minimize airborne dust and debris that can adhere to wet paint film.
- In environments where high humidity is present, use only exhaust ventilation to prevent the intake of moisture-laden air.
- In dry environments, utilize both intake and exhaust fans.
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Drying Schedules
The industry standard uses 77°F (25°C) and 50% relative humidity as common points of reference for drying times. The drying times information found on product labels and in product data sheets is based on this standard. They are approximate times calculated for ideal conditions.
- You may need to adjust drying times based upon conditions such as ambient air and materials temperatures above or below 77°F (25°C), and work environments above or below 50% relative humidity.
- It is important to note that in most production processes, material is applied at heavier film builds, which is an additional factor in adjusting drying times. The thicker film builds – in addition to lower temperatures, higher relative humidity, and poor ventilation – can have a significant impact on the curing of drywall compounds and paint material, as well as increase drying times.
- Achieving the desired outcome of the finished product, especially when working in low temperature/high humidity conditions, may require increasing allotted dry times between mudding, texturing, and painting processes. Each application introduces additional moisture into the process, and must be accounted for in the total drying schedule.