Apply gelcoat in suitable outdoor conditions

When applying gelcoat, the focus is on the processing temperature. It has a decisive influence on the result and, even with the best workmanship, can lead to later quality defects. The gelcoat has to dry out in the perfect balance between viscous and thin liquid so that it contracts too much or hardens when it dries through.

Temperature is the decisive factor

If the temperatures are too high during processing of the gelcoat, there is a risk of shrinkage. This process does not allow enough time to "gel" during drying. As a result of this so-called pot life, the chemical components are dried out faster than hardened.

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So-called under-hardening can occur, especially when applying gelcoat outdoors in summer. In the case of two-component gel coats, this effect can be partially compensated for by changing the dosage of the hardener, as long as the outside temperature does not exceed 25 degrees Celsius.

Temperatures below 18 degrees Celsius have a similarly destabilizing effect. Here it is often not possible to process the gelcoat properly. The increasing viscosity or viscosity makes the gelcoat less spreadable and it cannot dry out completely due to insufficient ventilation.

The high reactivity of the gelcoat ensures an optimal connection to the fiber-reinforced plastic that is supposed to surround or cover it. The reaction process can be restricted by tools that are too cold, such as rollers, brushes or spray bottles (€ 12.99 on Amazon *).

Humidity and draft

The application of the gelcoat is also influenced by the humidity. To a lesser extent, dry air has the same effect as a temperature that is too low and leads to thickening and an increase in viscosity. When the gelcoat dries, this leads to it becoming porous. The ideal value for applying the gelcoat is between fifty and 75 percent relative humidity.

Drafts can indirectly lead to overcooling of the freshly applied gelcoat. Strong wind accelerates the evaporation of the styrene and this process develops evaporative cooling. It can also lead to under-hardening that impair ventilation during the drying process.

Tips & Tricks If you apply the gelcoat when the outside temperature is higher than the specified ideal value, there will be, in addition to possible functional deficiencies, increased evaporation of the harmful styrene.