How to paint with topcoats

How to paint?

For professional applicators, the best method for applying topcoats is by conventional spray. This method will provide a very smooth and glossy finish as it requires high dilution and paint is “transported” by air which helps to level the surface. It requires the correct equipment and a certain expertise to get the desired finish. In addition some protection of adjacent areas is necessary to avoid dry spray contaminating the rest of the boat. However, brush and roller are very effective methods, very easy to use and they will provide a very good and professional finish.

1. Preparation

Before painting it is recommended to protect all areas which are not going to be painted. Use a solvent resistant plastic. In the case of spray application there will be lot of paint mist, thus it is important to carefully protect the underwater area as well as the deck.

Note: If the antifouling has already been applied, protect all the underwater area to avoid dust, paint mist and any other type of contamination that may affect the performance of the antifouling.

2. Protection

It is also important to protect yourself with the proper overalls, gloves, goggles and mask. Adhere to safety instructions on the back labels and technical data sheets.

3. Stirring

It is essential to thoroughly stir any type of paint, but this is even more critical with two components products, as drying will not be correct and it will not provide the expected gloss and hardness. For up to three litre cans, use a wooden/metallic stirrer and for bigger can sizes, use a mechanical stirrer. The stirrer must be totally clean to avoid contamination of the paint.

4. Application tools

  • Spray: Recommended for professionals but not always possible.
  • Roller: A medium or short pile mohair roller, resistant to solvent, is recommended. Alternatively a foam roller can be used, but with this type there will be more air entrapment, requiring extra brushing to achieve perfect finish. It is important to use a good quality brush to avoid loosing bristles that may be left on the paint to achieve a perfect finish. Different types of rollers provide different film thickness. In general, mohair rollers will provide more film thickness than a foam roller.

5. Surface preparation

Regardless of the application method, a professional finish can be achieved as long as the surface preparation is undertaken correctly. All areas to be painted must be washed with fresh water to remove dust, salts and other contamination. If grease or oil is detected the surface must be degreased with BoatWash. Once the surface is clean and dry, sand it to obtain a good adhesion and a smooth surface. The surface should be matt or semi-glossy, then follow the system below:

  1. Apply one primer coat as per the specification chart.
  2. If the surface has defects due to scratches, holes, etc. apply filler as necessary. Allow to dry and carefully sand with a P240 – P360 sand paper.
  3. After the filler, apply an extra coat of primer to seal the filler and prevent any solvent and resin entrapment which may affect the final gloss.
  4. Sand with P360-P400 sand paper. Thoroughly clean the surface before topcoating according to TDS.
  5. Finally, apply the topcoat.

6. Application

Apply by roller. Directly after roller application, gently brush the paint’s surface in a vertical direction using a wide, high quality brush. This is known as the «roll and tip» method. For spray application, Jotun can be contacted for detailed information on the technique to be used. When using roller or brush, apply two coats of the topcoat. By doing this, the levelling properties are increased, thus obtaining a high gloss finish, more uniform thickness and better durability and resistance.

Apply the recommended coats. Avoid applying under adverse conditions such as strong wind, high sunlight/ heat (specially at noon in summer time), low temperatures, high humidity or rain. It is not recommended to add extra solvents as these reduce the thickness applied and there will be more risk of sagging, splashes, etc (see TDS). However, if necessary to apply paint in strong wind or in high temperatures, it is possible to add between 5% and 10% (maximum) of solvent. Only use Jotun thinners and carefully read the product specific technical data sheet prior to use.

The best finish is obtained by crossing coats: the product has to be applied first in diagonal or horizontal direction and then re-paint vertically. By doing this, better leveling will be achieved, entrapped air can be more easily released and there will be a more uniform finish. It is advisable to use good quality brushes and rollers in order to avoid fibres on the wet paint. This working method should be repeated for all the following coats.

Hints for a perfect finish

  • Do not apply paint in very high or very low temperatures, in strong sunlight or in strong wind.
  • Wet the floor around to reduce dust on wet paint.
  • Stir the product thoroughly and every now and again during application.
  • If possible share the job between two people.
  • Use high quality solvent resistant rollers, preferably mohair type or foam type.
  • For the last coat a new absolutely clean brush should be used.
  • Apply by roller and tip off by brush.
  • Keep the brush at 45º angle to avoid brush marks.
  • Do not apply two component topcoats on top of a one component system.