Hardtop AS

Primers

Hardtop AS can be applied on exisiting two-pack polyurethane topcoats or over an epoxy primer, however it CANNOT be applied directly on to a single pack coating. The reason for this is that Jotun's Hardtop range contain a reasonably aggressive solvent (much stronger than white spirit) and this can react with single pack paint and act like a paint stripper causing the existing coating to blister and peel.

Any of Jotun's two-pack primers can be overcoated with Hardtop AS. For more informationin which primer is most suitable for your application please contact us.

Preparation

In order to achieve a high quality finish Hardtop AS should be applied directly to a smooth, clean and dry surface. Hardtop AS is a glossy topcoat and so any inperfections in the surface will be aggerated so it is important to flat back the existing coating before application. This also provide a mechanical key which aids adhesion.

Hints & Tips

Use thinner! One of the characteristics of Hardtop AS (indeed of all two-pack polyurethane paint) is that it can become tacky quite quickly and this can make it difficult  to keep a wet edge - especially if application is by brush and roller. Adding additional solvent will improve both the flow out and the final finish. The Jotun data sheet states that the thinner required is Thinner No. 10, however we disagree. Thinner No. 10 is ideal for use when application is by air-less spray, but when using conventional airspray or brush and/or roller we recommend using HQ Polyurethane Thinner. As the name suggests this evaporates much more slowly which improves the application properties enormously and also keeps the gloss levels at a maximum.

Only paint in good atmospheric conditions. This may seem like common sense, but changes in the weather can have a large impact on both the application properties of Hardtop AS and the final finish. The ideal painting weather is a dry, cool and calm day, but if you find yourselves being forced to apply Hardtop AS in tricky conditions then:

- if it is hot and/or windy then Hardtop AS will dry quickly and so it is even more important to have some thinner to hand. At higher temperatures the pot life of the mixed components will be reduced so only mix up what you can use in a couple of hours.

- if it is cold the curing time (this is the length of time it takes for the chemical reaction between the two components to occur), and the drying time will be increased. This means the paint will be wet and soft for longer.

- avoid painting if it is wet or very humid. Moisture in the air can prevent Hardtop AS curing properly and can also take the edge of the gloss. You must apply the paint only when the temperature is a minimum of 3°C above the dew point. The dew point is the temperature at which condensation starts to form and is a relationship between air temperature and humidity. You can calculate the dew point by using the table below:

Polishing

Hardtop AS is an acrylic polyurethane which means that runs, inperfections and small scratches can be carefully repaired by polishing. This is because the heat produced when polishing will very slightly melt the top layer of paint and remove blemishes.