Secrets of a topcoat
Painting the final topcoat outdoors can be a challenge, so Jake Kavanagh called in an expert for tips to beat the bugs and dust. Here he shows how to achieve that perfect finish

Many years ago, a master painter was putting the finishing touches to the side of a Fairey Huntsman. By using a fine brush and the very gentlest of pressure he had achieved a finish that was almost too good to be true. Suddenly, a passing boater bumped against the wet hull and left a long smear. The painter was horrified. ‘Hey!’ he cried. ‘You’ve just brushed your sleeve against my paintwork.’

The boater paused, and glanced at the patch of gloss on his arm. ‘Oh, that’s OK,’ he said. ‘It’s an old jacket…’
Over the past two issues we’ve been painting a small, battered glassfibre yacht with a two-part polyurethane paint system. This month, we’re laying on the pièce de résistance – the final topcoat which should make our boat look like new again.

Two-pack paints are harder wearing than their single-pack counterparts, and stick to GRP like a fly in ointment. They give a rich, deep gloss, but need the right conditions, and a fair turn of speed from the painter. Drying time is measured in minutes, rather than hours.

We had the worse case scenario right from the start. The boat was squashed into a space at the back of a busy boatyard and fully exposed to prevailing winds. Then there was the dust from the forklifts working the nearby boat-racks, and seemingly driven by fans of Damon Hill. Finally, there was the hull colour – a very attractive dark blue, which meant it heated rapidly in the sun. As with all paint, this accelerated the drying considerably.

The results, though, were impressive. The undercoat was rich in pigment and sanded easily – which was just as well. The boat was transformed from its chalky, tired looking former self to a confident little cruiser with just the first – and slightly botched – undercoat.

But what happens at the most critical stage? Richard Jerram is one of International Paints’ top technical advisors, and he came to the yard to show us how to beat the dust, paint runs and brush marks to get a truly outstanding finish.

Two-pack polyurethanes are tough but sensitive beasts.

• The curing agent, a clear liquid in a separate can, has to be mixed at the precise ratio to set the paint off.
  
• High humidity (over 70%) could cause ‘blooming’ which is a loss of gloss surface.
  
• The paint ideally needs to go on at 15-20C° (59-68°F)

Preparation is the key
Previously, we had:

• Sanded the hull
• Faired all the gouges with epoxy filler
• Applied two coats of undercoat to give depth of colour and to avoid patchiness in the topcoat
• Flatted back the final undercoat and then washed the hull down to remove all the dust

As our boat was staying blue, we used a blue undercoat – but had we changed to a lighter colour, two coats of white would have been used instead.

1. All of the areas to be painted must be instantly accessible. You need to be able to keep moving and don’t want to waste time repositioning ladders. If a wet edge of the paint goes hard, it will leave a visible ridge.
   
2. Have all your tools to hand. Make sure you have enough paint trays, enough paint, and spare rollers and tipping brushes ready to go.
3. Down with dust! Saturate the area around the boat with water to stop any dust rising, and try to pick a day when there’s no wind.
4. Check the masking, as tape can be dislodged or damaged during the painting or curing times, so just check it’s all still in place.
5. Give the gunwale a wipe with tissue just to ensure that all residual moisture from the wash-down has been removed.
6. Wipe any dust or grease from the paint trays using thinners.

Top tips

• A quality finish needs quality tools. We used a 3in ‘Fine Finish’ nylon tipping brush, and ‘Fine Finish’ decorators’ rollers. We found the cheaper ones from some DIY outlets tended to break up after a short time.
• Only touch the hull while wearing gloves. Sweat and oils on your skin can be transferred to the hull, which can affect the paint.

1. Open both cans and stir the base paint thoroughly as the contents settle with storage. Always use a clean stirrer. A flat, ruler-type stick works best.
2. Add the curing agent. The tins of base colour are deliberately only two thirds full, so you can tip the entire curing agent into the main tin for the right ratio. For smaller amounts, use a measuring cup which has the ratios marked on the side. Stir well and in a random pattern. The curing agent has to be thoroughly mixed with the base.
3. Decant the amount of paint you think you’ll need into a measuring cup (you’ll have discovered from the undercoating stage how far the paint will go, and can become quite accurate). Add between 5-10% thinners depending on how warm the day is – the warmer the day, the more thinners. We used a ratio of about 8% thinners.
4. Again, stir well. Lifting the stirrer out and letting the paint fall back in will show how consistent the mix is.
5. To minimise the chances of dust settling on the hull, give it a final wipe with a tack-rag just as you are about to paint. The tack-rags contain a wax, so only wipe them gently over the hull. Put on too much pressure, and the wax is transferred to the glassfibre, which could interfere with the finish.
6. Pour enough paint into the paint tray so it reaches to the edge of the incline. Dip in the tipping brush so the ends are pre-primed, and load up the roller. Move everything you need close to the hull.
   

Top tips

• Some tin lids have a double lip. Try to make sure you’ve inserted the lid remover under the uppermost lip, and not the second one. If the lid is putting up a fight, this may be the reason.
• Pour paint into the measuring cup carefully. If it slops it will obscure the graduation marks for the thinners.
• Cover over the tin when leaving it for any time, just in case a seagull decides to add to the formula. Although activated, the paint will stay workable for a long time in its tin.

‘Don’t be afraid of it,’ Richard Jerram advises. ‘It’s only paint.’
His secret is to be bold and confident with the brush, using a series of strokes, diagonally, and then finishing with a downward ‘tipping off’ motion

1. If you’re right handed, start from the right. Begin at a hard edge, ie the bow, and be prepared to end at a hard edge – the transom. You won’t be able to stop for more than a minute or so along the hull, or the wet edge of the paint could dry.
2. Roll the paint on by driving the roller in several directions for an even coverage.
3. Now work the tipping brush across the paint, diagonally at first, and then finishing with downward strokes. The idea is to remove all the ‘orange peel’ effect from the roller.
4. Start the next area a few inches beyond the wet edge, and work back to it. This allows the roller to empty some of the paint before it hits the wet edge again, and gives a more even coverage.
5. Work the tipping brush right across the area, especially over the seam between the panels of paint. Finish off again with the downward strokes.
6. Keep going, rolling vigorously, and then quickly tipping off. Note how Richard is holding the brush, using all his fingers for greater control.
7. If you need a comfort break, stop at a natural junction. You may decide to call a halt here and start again a following day. The bow and quarters form a natural break line, and some hulls will have other places you can stop. If you decide to keep painting, the tipping brush can be used to merge the paint seamlessly around the corner.
8. By the time we had done one side of the 21-footer, which only took Richard about 30 minutes, it was time to change rollers, as the first one was starting to soften and lose its shape.

Top tips

• Don’t use paint pads! International’s Perfection has been formulated for use with a brush and roller. The solvents tend to cause paint pads to shed hairs in alarming amounts.
• If an insect lands in your gloss coat, leave it alone. You can extract it once the paint has dried. ‘If it looks like it might move, pick it out,’ Richard advises. ‘You don’t want it walking across your work.’
• The best way to remove the old roller is simply to knock the shaft against a suitable post (see above). The roller will fly off, saving messy fingers.

Unfortunately, there can be a lot of wastage with two-pack paints. Unused activated paint is simply allowed to go hard before being binned – it can’t be poured back and reused like ordinary paint. Rollers are also deemed one-use. Brushes, however, can be thoroughly cleaned out with solvent, (it has to be the right solvent, such as Thinners No9) and then washed in warm, soapy water before being allowed to dry.
Masking tape should be removed as soon as possible, and is one of the satisfactions of the job. Solvent can be disposed off at the yard’s solvent bin.

The gloss coat should be left until the next day before being wiped over with a Scotchbrite scouring pad, and then recoated. There is no variation in the thinner ratios or mix, and the second coat will add extra depth to the first.

If the job has been left for a while, the topcoat will need a gentle rub down with 400-grit (perhaps 280-grit to flat off any runs) before recoating.

International advises that the final gloss coat is left unmolested for about six days for it to fully harden, so avoid having the boat lifted or moved until then.

Et voilà! Although our rubbing down of the undercoat hadn’t been quite up to Richard’s standards, he achieved a superb finish in a very short time. We used about 500ml of paint for one coat on the 6.4m (21ft) hull, and she looks great. The 80-micron layer of gloss will cure back to just 40 microns, which is why a second coat is recommended.

To keep the gloss in good order, all we have to do is wax the surface at the start of every season with a UV-resistant wax. The cost of materials for this small boat was around £120, including rollers, paint trays and tack-rags, and if the gloss lasts for the five to seven years as claimed, that’s not a bad investment.
Obviously, a lot of time was spent in the preparation, but when you see the results sparkling in the sunshine, you sort of forget about all that.

Now, where exactly did that insect land…?

We used Perfection from International Paints for our demonstration, but the painting techniques shown apply to most brands of boat paint.

Perfection
Perfection is a development of International’s hard-wearing 709 polyurethane. Extra flow additives have been used with the DIY painter in mind, and the system has been formulated for brush and roller application. There is a more limited choice of colours than its one-pot alternative Toplac, and it is more expensive, but the results are superb. Only specific thinners can be used, which adds to the cost.
The double-lips of the tins gave us some battles until we found the secret, and the curing agent tins tend to jam up and become sticky if used more than once, but International tells us they are looking at possibly repackaging this component into better containers.

What does it cost?

• Perfection undercoat: £24.99 for a 750ml tin
• Perfection top coat: £30.95 for 750ml
• Thinners No9: £12.49 for one litre
• Tipping brush: £5
• Rollers: around £3-4 for a kit with tray

Free movie
International has produced a free information CD which shows the whole painting process as a step-by-step film, from the initial sanding down to the final gloss coat. They also have free brochures available which illustrate the various steps, along with other products in the range. Contact their switchboard on
tel: 02380 213146

• Thanks also to Richard Jerram, one of International’s team of technical advisers. To talk to Richard, or his colleague Barry Corke, call the technical helpline on
  tel: 02380 213134 or email:
  richard.jerram@internationalpaint.com
  
• International PAINT Ltd
  24/30 Canute Road, Southampton,
  SO14 3PB,
  
• web: www.yachtpaint.com