Drying time is highly temperature dependant- whereby temperature refers to surface temperature during the drying process. Low temperature delays drying, and higher temperatures speed up drying. Every 10% increase in temperature will have a significant effect in drying time. The chemical curing of two-component products usually requires a minimum curing temperature of + 10 oC since the curing process will draw to a halt at lower temperatures. A second important factor in the drying process is the relative humidity. The higher the humidity, the longer the drying will take. Relative humidity above 80% is critical (surfaces can become matt, with the dew point being reached in localized points). Furthermore, air circulation and sunlight should also be taken into consideration. Since solvent vapors are heavier than air, when working in a closed room, ensure good air circulation to avoid the slow drying and mat surfaces that vapors can cause.
Dew point
Dew and frost are well known phenomena. Their formation is due to the different saturation levels of water in air at different temperatures (a cubic metre of air can hold approx 1gr of water at –18 oC, 5gr at 0 oC, 20gr at +23 o C and around 30gr at +30 oC). When the maximum amount of water, which can be held by the air at a given temperature is reached, the relative humidity is said to be 100%. Cooler surfaces can become covered in a dew film, which can be invisible, brought about, for example, through wind, evening cooling, tanks being filled, drying rain, or through drying paint. For this reason it is usual practice only to carry out coating work when the temperature is at least 3 oC above the dew point (or at maximum relative humidity of 80%)
Intervals between Coats
For all one and two component products both a minimum and maximum interval must be closely adhered to. The interval between coats is applicable not only to re-coating of the product with itself, and also to coating with further products. An “early” application of a further coat leads to solvent enclosure, resulting in deficient curing. In turn this will cause blister formation when under water loading. “Late” application of the following coat hinders bonding with the new coat since, in the case of two component products; the material is already totally cured. Where the maximum interval is between coats has been exceeded it is essential, also in the case of one-component products, that the surface be matt-sanded before the new coat is applied (ensuring the mechanical fixing of the newly applied coat).
For this reason many thin layers are recommended, rather than the fewer thicker layers. Where lacquer is applied too thickly it will not harden properly, which can lead to surface wrinkling, “tears” (droplets) or ridges which will have to be laboriously sanded down the years.
Systematic Protection of Wood
The painting and renovation of yachts and boats of wooden construction is one of the most satisfying jobs of all, providing a real feeling of achievement. The result of a good coating is immediately visible, and the lengthy preparations are soon forgotten.
A paint coating not only brings out the natural beauty of the wood, but also ensures the value of the vessel almost indefinitely - with minimal effort and expense. Using our coating system – specially developed for all types of wood used in boat construction – annual overhauling work is kept to a minimum. With correct application of the product, the time taken will hardly be more than that necessary for a boat constructed of fibre glass reinforced plastic.
Even when it sometimes appears to be the case the correct use of a brush and paint is easy enough. Inexperienced painters can achieve good results in a relatively short period of time – providing the following simple, but important guidelines are followed. Even the best paint will, in the long term, not bond properly with a poorly prepared surface.
Hence the first rule:
The better the subsurface, the longer the paint will hold, and the better the wooden surface will look.
Never paint directly from the tin. It is inevitable that dust particles will be transferred via the brush into the tin. For this reason it is recommended that the approximate volume of paint required be poured into an additional container. One of the secrets of a good surface is a thin application.
Treatment of Teak Decks
In bygone years it was generally sufficient to scrub down a teak deck with green soap every now and again. This would lend the wood a beautiful white-gray tone, which would protect the surface from the elements like patina. Sadly this is no longer sufficient. The wood needs protection from aggressive industrial emissions, otherwise dirt will penetrate too deeply to be removed, damaging the wood, particularly between the grains.
The products Teak Cleaner, Teak Refreshner, and Teak Sealer provide long-term protection against the harmful effects of air pollution and restore and maintain the wood’s natural beauty. The simplest method to get strongly soiled old grayed teak wood clean:
The teak deck is soaked thoroughly with a lot of water (excess water has to be removed with a cloth)
Apply cleaner with a soft brush evenly and saturated to the damp teak area. After this the complete surface is worked thoroughly with a hard brush or scrubbing brush. The damp surface must not be allowed to dry during this process.
Then the area must be flooded with a lot of fresh water and excess water removed with a clan cloth. The damp area has to be treated Teak Refreshner. Teak refreshner is applied with a soft brush evenly and saturated. After a few minutes the team area can be rinsed with a lot of fresh water. After thorough drying the treated teak wood should be sealed with Teak Sealer.
Further benefits:
Following thorough treatment with Golden Teak only minimal maintenance is necessary as penetration of dust and aggressive dirt into the wood is hindered.
In contrast to oil treatment, the deck remains non-slip.
Preservation of the wood reduces wear; the surface is physically protected
Osmosis Damage in Polyester / Glass Fibre Reinforced Plastic
Osmosis is defined as the process of “corrosion” or damage of a plastic surface. This happens due to the water molecules intruding the gel coat. The water elements react with the chemical components that exist in polyester resin producing new acids which in turn create blisters on the surface as the water forces to escape.
GRP hulls are generally speaking a matrix including polyester resin reinforced with glass fibres constructed in layers. These plastic layers are not homogenous in their construction and as such, there are voids and holes at the points where the polyester resin meets the glass fibre layers. In due course, when the hull is at sea, water molecules will intrude the gel-coat surface in order to stabilize viscosity pressure
These water molecules will get trapped in the polyester layers, and due to their non-homogenous construction, will start the process of hydrolysis and will damage the polyester layers as they force themselves out. This process of damage to polyester layers is not visible until the blisters start forming themselves on the hull surface. The acids get crystallized and cannot be removed with simple washing method.
Water molecules react right where the polyester layers bond with each other creating glycol acid. It’s what gives the blisters the recognizable odour of vinegar. These osmosis blisters are not just a decorative problem but also a visible sign that the polyester’s hydrolysis is affecting the layer’s surface. When the first blister appears it means that the level of bond between the polyester resin and fibre glass layers has deteriorated deep into the hull which in turn can lead to a loss of 20 –30 % of construction force and mechanical stability.
In accessing the extent of the damage the following factors are important:
Quantity, size, local distribution and pattern of blisters
Affected areas (as a percentage), delaminating and whether mechanical stability is still ensured
The following have come to be recognized as causes of real osmosis:
Gel coat is too thin or micro porous, or too highly filled.
Air voids
Insufficient hardening or preparation
Hydrolysis
Ageing
Natural diffusion of water
Damage due to chlorinated
hydrocarbons such as methylene chloride, dichloromethane and trichloroethane
The product labeling will indicate whether any of the substances mentioned above which would be damaging to GFRP materials, are contained in the product. To avoid re-occurrence of real osmosis, yachts and boats, whether new or in use, should be preserved with a preventive coating of epoxy primer of the recommended film thickness.
Filling works
The success of any filling work is generally dependent on a number of factors:
GFRP, steel and aluminium should be well cleaned and free of grease. After sanding but before filling, a layer of epoxy primer should be applied. Then apply the chosen coating system in accordance with the corresponding instructions.Try to avoid filling work on wooden constructions. Should smaller areas require filling, the following points should be noted:
Nordic woods should be well sanded and dust free before application of filler directly to the wood.
Hard woods and tropical woods should be washed with 2K Thinner to remove natural elements before sanding and removal of dust. Small areas can then be repaired. Then apply the chosen coating system in accordance with the corresponding instructions.
