The Australian climate brings on a host of coating and finishing problems. It is important for the applicator to be aware of some of these common problems and the best course of action they can take to deliver a quality floor finish.
When the temperature reaches 24o C, coatings start to become difficult to work with and the application can be negatively affected. When temperature exceeds this figure, especially on a daily basis, this will have an even greater negative effect on the application of the coating.
On any coating manufacturer’s technical data sheets, there will always be a reference to the maximum and minimum temperature the floor finish can be successfully applied in. Obviously coating in conditions where the temperature exceeds these parameters will make the coating unworkable and troublesome. Additionally, the applicator must not forget that in the warm and hot summer months, buildings and timber flooring will absorb and retain heat for lengthy periods. When a coating is applied in this ‘hot house’ type environment, the floor finish will dry faster than normal as it absorbs the radiant heat of the floor and surrounding structure.
An important element to consider is that high temperatures greatly increase the rate of drying and curing. This results in a loss of ‘wet edge’, making any coating more difficult to work with. Additionally, water-based floor finishes are extremely temperamental and less forgiving in warmer conditions.
The problems that occur in summer for solvent-based, water-based and to a lesser extent oil-type finishes are:
Viscosity increases: this means that the coating will become thicker to apply as the solvents flash-off faster. This will result in poor flow and levelling causing:
- Orange peel
- Thickening of the coating, especially two component products and solidification resulting in small gel particles
- Poor levelling
- Application marks from the roller overlapping on sides and where it stops as the finish dries
- Brush marks around perimeter of room
- Air bubbles from the roller are trapped on the surface and do not burst in time as the top film of the coating dries
- Inconsistent sheen
- Reduced working time because of the loss of the wet edge.
Solar gain: sunlight beating down on timber floors through windows will heat the wood to temperatures far exceeding the air temperature. If the floor is dark because it has been stained, or if it is a dark colour timber, the floor temperature will be even greater. When the coating is applied to a hot floor:
- It sets quickly, drying too fast
- It can cause the coating to ‘blister’
- It will cause the coating to not penetrate and bond properly to the timber, causing it to delaminate later.
Storage: do not use warm finishes on colder floors. When coatings are kept in vehicles or stored in sunny conditions, the coating will not flow and level correctly.
- When applying a warm water base coating on a colder surface, small fine bubbles will be trapped in the drying film of the coat as the air in the wood is warmed up.
- When water base coatings are warmed up the defoamer additive can be affected resulting in increase in bubbles.
Additionally, the shelf-life of coating and its future performance will be compromised.
In summer in order to avoid the problems discussed above, the applicator needs to focus on factors that will reduce the incidence of problems:
- Keep the interior of the house and/or room cool, and avoid heat build-up over hot days by ventilation and if possible by running air conditioning for a suitable duration prior to commencing coating. Do not run the air conditioning while coating.
- Cover the windows and doors with an opaque material a number of days prior to coating to avoid sunlight heating the flooring.
- Coat in the cooler part of the day, such as early in the morning, before sun heats the flooring.
- Avoid air flow while coating by keeping windows closed. However, once coating is tacked off, ventilate the area to facilitate curing.
- Do not apply the coating too thinly. With some finishes a thicker coat will keep the wet edge longer.
- Acclimatise coating before it is applied. Do not store coating in vehicles at any time. Never apply a coating that is warmer than the floor.
- Always store water-based finishes in a cool place and during transport store a ‘cold box’.
To find out more, visit the National Wood Flooring Association of Australia website.