USEFUL TIPS
ABOUT PAINT PRODUCTS

  • WHAT PAINTS ARE USED FOR
  • Paint can be defined as a mixture of chemical compounds intended to form a film with sufficient mechanical and physical strength to protect the painted surface from external agents over time. Paint is used both to protect and decorate.

    These products are used in almost all stages of boat painting: preparation, priming, protection and finishing. Although no paint is used during preparation, getting this stage right ensures the ultimate success of the job. Poor preparation usually means disappointing results. The next step after preparation is applying the primer. The primer protects the substrate and also guarantees that successive protective layers and finishe will adhere to the surface, avoiding delamination. After primer application, the undercoats provide a protective layer, which prevents water, humidity and atmospheric agents from coming into contact with the surface and causing it to deteriorate (metal corrodes, wood rots and GRP suffers from osmosis).

    A protective layer with a minimum thickness of 300-600 microns (when dry) for submerged parts and 250-350 microns for areas above the waterline is required to ensure sufficient protection.

    The final step is to apply the finish. These products are used to improve the appearance of the boat and the surface properties of the materials used (colour, gloss), or to provide specific protection (antifoulings). For a perfect finish, the surface may need filling to obtain a smooth substrate. To achieve a good enamel finish, the application of a basecoat is recommended, which provides a protective barrier and also a smooth surface, eliminating rough spots left by the filler.

  • WHAT THEY CONTAIN
  • Paints have four main constituents: binders, solvents, additives and pigments. The main component is the binder, which consists of polymers or resins that form a tough, dry film adhering firml to the substrate. Solvents are volatile liquids used to dissolve and disperse the other components. At the same time, by reducing the viscosity of the paint, they make application easier. The evaporation of the solvent controls the cross-linking of the binder and therefore the formation of a uniform film, which is why the correct use of thinners is so important. For environmental and safety reasons, the use of solvents is being reduced or eliminated, with liquid resins used in their place. Pigments are micronised powders that give the paint its colour, hiding power and other special characteristics, such as the antifouling properties of pigments based on copper or zinc salts. Additives are components used in small quantities to improve the properties of a paint (drying, resistance to ultraviolet light, ease of application, pot life, etc.).

  • HOW THEY ARE CLASSIFIED
  • Paint products are categorised as varnishes, paints and enamels. Varnishes are transparent and mainly consist of binders, solvents and additives, with no pigments. They are generally used to protect and improve the appearance of the substrate (wood, kevlar, carbon fibre). Paints also contain pigments and/or extenders that give them hiding power and are called enamels when they have particular characteristics such as gloss and resistance to weathering. Fillers are paint products too, characterised by a high percentage of extenders so that they can be used to level cavities and imperfections in the surface. There is an important difference between one pack and two-pack paints. One-pack paints have only one component and the film is formed by the evaporation of the solvent. While these products are easier to apply, they have limited durability. Two-pack paints require mixing in a specific ratio. Filming occurs by means of chemical cross-linking of the two components. This process produces longer durability and better protection.

  • HOW THEY ARE APPLIED
  • When you are planning to paint, always remember the following guidelines, which will ensure your safety and prevent you from making mistakes.

    • Mask the edges of the area to paint using adhesive tape. Always remember to remove the tape immediately after the application of each coat, especially when using two-pack paints.
    • Only dilute as required using the recommended thinner.
    • After opening the can, ensure that the paint is evenly mixed to obtain a uniform consistency and colour, especially if the pigment (at the bottom) has separated from the binders (at the top).
    • If you are using a two-pack paint, it is important to mix the two components separately before pouring component B (hardener) into component A (base) and then mixing until the colour is uniform. When you are preparing a two-pack paint, take into account how much paint you will be able to use before it becomes unusable (pot life).
    • Comply with the recommended drying times even if the paint appears to be dry.
    • Apply the paint at a temperature of between 15 and 25°C and a humidity of less than 75%. It is possible to work at higher or lower temperatures than these but you must expect the drying characteristics to change.
    • Remember to take into account the temperature throughout the entire cross-linking period, especially overnight.
    • Never paint in full sunlight. If necessary, create shaded areas using tarpaulins. Do not paint in strong winds or misty conditions.
    • Do not change the ratio between the base and the hardener in two-pack paints because this will alter the chemical characteristics of the product.
    • If you are unsure of the paint previously used, it may or may not be compatible and we therefore recommend painting a small test area first. Should any problems arise (cracking, bubbles, "bleeding" or softening of the previous paint), please contact Veneziani Yachting. Normally, you simply need to apply a coat of suitable sealer.
    • To check the evenness of the paint, use a paint thickness gauge at various points to measure the thickness of the wet paint “coat by coat” before the solvent evaporates. If the dry paint volume is 100%, the dry and wet thickness will be equal; if it is 50%, the dry thickness will be half as much.
  • HOW TO OPERATE IN SAFETY
  • These basic hygiene and safety rules are always applicable when applying paint to boats

    • When handling cans over two litres, always check their weight as they may cause back injury when lifted.
    • Carefully read the instructions printed on the can before starting to paint.
    • Check the safety label in particular for any special precautions that must be taken for each product.
    • If the necessary documentation is not available, please consult the website www.venezianiyachting.com.
    • Certain paint components (particularly in antifoulings) cause irritation if touched, are harmful if inhaled, and are sometimes toxic. These risks, which vary from product to product, are clearly indicated by the symbols on the safety label, along with any special precautions.
    • Do not smoke during application.
    • Do not use compressed air to clean your clothes, especially if solvents are present.
    • Almost all paints contain flammable solvents which evaporate during drying. Be careful not to inhale the vapours, especially in a closed environment. Ensure adequate ventilation to avoid the risk of fire or explosion and use an appropriate mask.
    • We advise wearing gloves, a mask and protective goggles.
    • Always sand using wet sandpaper on a wet surface, particularly with antifouling products, and wear gloves, a mask and protective goggles.
    • Use a water-based paint stripper if possible to remove old paint, like AQUASTRIP from the Veneziani range. Dry sanding or flame cleaning should be used only where it is impossible to employ a different method.
    • When you have finished work, or when taking a break, thoroughly wash your hands with soap and water or a hand cleansing agent. Never use solvent-based thinners or strippers to wash your hands.

GLOSSARY

  • DRYING
  • There are two stages in the paint drying process, relating to solvent evaporation and/or the degree of cross-linking. A product is “dust-free” dry when airborne dust particles will not adhere to the surface of the film A product is “touch” dry when it can be handled without leaving marks on the film. The paint only achieves its maximum performance when the drying time has completely elapsed (drying time before use). Always comply with the recoat times given in the technical data sheets.

  • HYDROPHILIC
  • This is the opposite of hydrophobic. A hydrophilic surface is easily wetted and incorporates or retains a layer of water. Hydrophilic antifoulings retain a layer of water (sponge effect) and provide ongoing protection because the surface is always active. For this reason, the effectiveness of the antifouling can be planned: the more layers of antifouling are applied, the more effective it is.

  • MIXING RATIO
  • This is the ratio of base (component A) to hardener (component B) for two-pack products. The mixing ratio is reported both by weight and volume in the technical datasheet for each product. Pay careful attention to this information because the ratio is mandatory and must not be changed. Remember that using more hardener not only doesn’t make the paint dry faster, but also affects its properties and quality.

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  • POLYMERISATION
  • A polymer is a compound consisting of many single molecules called monomers. Polymerisation is the process in which two or more molecules combine to form a new molecule. Plastics are typical polymers: polyester, polypropylene, etc. In the case of varnishes and oils (linseed oil, tung oil, etc.), polymerisation is a natural process that takes place by oxidation, promoted by the oxygen in the air. The polymerization of two-pack paints, on the other hand, is a chemical reaction, where the base and hardener interact rapidly to form a highly cross-linked polymer. For this reason, two-pack coatings usually have better chemical resistance than one-pack coatings.

  • POT LIFE
  • This is the time during which you can apply the A+B mixture (base+hardener) of a two-pack product after mixing. When this time has elapsed, the mixture sets and can no longer be applied. Any attempt to thin the product is pointless and dangerous, because it alters a chemical reaction already in progress. The pot life given in the technical instructions refers to 200 g of product measured at 20°C. Please bear in mind that pot life is inversely proportional to temperature, meaning that it increases at lower temperatures and decreases at higher temperatures.

    For example, if the pot life of a product is one hour at 20°C, at 30°C it may be only 30 minutes.

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  • PVC
  • Pigment Volume Concentration is the concentration by volume of the pigment in a dry film. Coatings with a high PVC value contain more pigments and are therefore matt, with high hiding power. Coatings with a lower PVC have a glossier finish and normally better chemical resistance.

    PVC is a critical factor in antifoulings as it affects the leaching rate of the biocides.

  • SOLIDS BY VOLUME
  • This is the ratio between the solid and volatile substances in a paint product. The dry volume is the part of the product which forms the protective film. The solvent evaporates after performing its function of facilitating the application of the product. The dry volume of a product can be used to calculate the theoretical coverage at a certain thickness. A product with a solids by volume content of 50% means that 100 cm3 must be applied (0.1 l) per m2 to obtain a wet film 100 microns thick and a dry film 50 microns thick. In a product with a solids by volume content of 100% (solvent-free), the wet and dry film thicknesses are the same.

  • SPECIFIC WEIGHT
  • This can be defined simply as the weight of one litre of the product and is expressed in kg/L. Normally, the binder and solvents in a paint have a specific weight equal to or less than one (i.e. they weigh the same as water or slightly less).

    Pigments, however, are heavier and some (copper or zinc compounds, for example) have a specific weight of over five. This is why cans of antifouling are so heavy and why the pigments tend to settle on the bottom of the can, a problem that can be mitigated by using special additives.

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  • THEORETICAL AND EFFECTIVE COVERAGE
  • The coverage indicated in the technical data sheets refers to the theoretical value for the product, which can be calculated using a simple formula. When applying a paint, the surface actually covered is less than that indicated by the theoretical coverage, since there is always some loss of material. The amount of the loss depends on the condition of the surface, the type of products used, the atmospheric conditions and the method of application.

    The percentage of product lost because of the first factors is impossible to estimate in advance, while the loss percentages relating to typical methods of application are as indicated in the “Loss percentage” table below.

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    In order to obtain the practical coverage, the theoretical coverage must be multiplied by the loss factor. When purchasing products, the surface area to paint (in square metres) is required to calculate the correct amount to order from the retailer based on the technical data sheets.

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  • THIXOTROPY
  • This is a form of apparent viscosity. A thixotropic product seems dense and viscous, but in fact flows easily when applied by brush or roller. When stirred energetically, a thixotropic product returns to its normal viscosity and becomes more liquid. In a thixotropic product, the pigments don’t separate from the binder and therefore don’t settle on the bottom of the can. Application by brush or roller is easy and the product doesn’t sag or run during application. However, it may become difficult to level and has a tendency to leave marks when applied by brush, as well as to produce an orange peel effect when applied by roller. For this reason it is important to use the appropriate type of tool based on the product to apply. The product should be stirred vigorously before application and if necessary slightly thinned.

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