| 31
14 13
12 11 10 9 8 7 6 5 4 3
2
1 0
510 15 20 25 Air temperature ̊C Above left: Drying parameters for water-based paints Above right: Average moisture content in exterior joinery 30 35 40
14 13 12 11 5 0
yet be fully effective. As temperatures lower, this stage takes much longer to complete. Next, the coating begins to chemically crosslink, improving toughness and adhesion. In summer or good factory drying conditions this can happen in a few days. However, curing slows dramatically in cold, damp conditions and can stop completely near freezing.
If joinery is exposed to the elements before curing is complete, it remains vulnerable until warmer drying conditions return and the curing stage is completed.
Above: Cold weather introduces risks
SIX PRACTICAL STEPS FOR THE FACTORY 1. Keep paint in a heated store before use and never leave paint cans on a cold concrete floor.
2. Follow the film thickness specification. Over application is wasteful and slows the drying process
3. Ambient factory drying – maintain a minimum temperature of 15-22°C in the spray booth and drying area, using a background heater or ducted, filtered, warm workshop air. Use simple fans to maintain air circulation.
4. Leave heat and air circulation fans on overnight (timed). In cool, still air very little drying will take place.
5. Don’t try to accelerate drying by blasting hot air at joinery items. This will speed up surface drying, but trap moisture in the film and impact on the coalescence process. (Contact Teknos for advice on forced drying.)
6. Delay wrapping finished joinery for as long as possible. Wrapping and storage in an unheated despatch area can slow or stop moisture release from the factory-finished system which can subsequently prevent full coalescence and curing where not achieved in the factory.
DON’T FORGET THE TIMBER ITSELF The ambient moisture content of exterior joinery varies significantly through the year and is generally independent of any treatment or finishes applied to it.
Dimensional change is a function of standard species and grade, but broadly speaking, standard species dimensions vary by about 1% for every 3% change in moisture content.
In winter, it is not untypical for joinery to leave the factory at around 10% moisture content, sometimes lower if using laminated sections, then rapidly condition to 18-20% on site. The resulting 3 - 4% dimensional changes cause joints and seals to open, letting moisture penetrate unprotected end grain and rebates.
SIX PRACTICAL STEPS ON SITE 1. Remove airtight packaging, prior to storage, to allow free ventilation of the joinery.
2. Store joinery off the ground on suitable bearers and cover with a permeable sheet to protect from contamination.
3. Storage areas should be well ventilated and not subject to extremes of temperature. Avoid unsuitable storage, such as metal box containers, which may be subject to condensation and become very hot in direct sunlight. Water can also collect in protective wrapping leading to saturation of some components.
4. If joinery is installed prior to completion of internal wet processes, gentle internal heating, good ventilation and the use of dehumidifiers will greatly reduce the risk of blistering and delamination as the building dries out.
5. Remove plaster and other building materials contamination immediately with a solution of detergent and rinse with clean water.
6. Ensure that any on site assembly or modifications are fully protected: particularly cill joints, glazing beads and glazing systems. Unprotected end grain exposed by site modifications must be effectively sealed and protected – such as with two generous brush coats of Teknoseal 4000 – recreating the full paint system.
FINAL WORD
Winter doesn’t have to mean coating problems. By monitoring temperature, airflow, and moisture levels, joinery manufacturers can maintain a high-quality finish and avoid costly rework. ■
FURTHER INFORMATION For more technical advice or guidance, visit
the Teknos Technical Library via
teknos.co.uk or contact
sales@teknos.co.uk
www.ttjonline.com | Spring 2026 | TTJ
Drying time (hours)
Equillibrium moisture content (%) January
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