two-pot paints

[AOWYN]

I want to paint a GRP dinghy and would appreciate other peoples' experiences with brush-painting two-pot poly paints. Is Awlgrip any better than Perfection? Why do Awlgrip say that you shouldn't polish or buff the finished paint?

Thanks in advance

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[tillergirl]

I helped a chum two pot the topsides of his 26 ft Mystere earlier this year. The plan was that I would roller it on and he would follow behind laying off with a brush. We did two undercoats and three gloss coats. The first attempt we had to abandon the laying off because of drag marks and it required a light sand to remove the imperfections (not really a probelm). Next time we cut the mix down with thinners but again abandoned the laying off because of brush marks. When getting to the gloss coats we kept increasing the amount of thinners added each time and the thinner the mix the better it went. On the top coats we found the roller left a better finish and the second person instead of laying off was constantly keeping the mixed stuff stirred, refilling the paint tray (so we didn't have too much in it at any one time), replacing the roller as soon as there was any dragging and watching for holidays. Was a very presentable finish in the end which I think he intends to buff this winter and overcoat with a final undercoat and gloss in the following spring. I'm no expert but one painting and the other facilitating the business seemed to work better than laying off. The roller provided a lot better finish than the paintbrush. He used international

Hope this helps.

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[AndrewB]

I've used both Awlgrip and International, the latter many times. Awlgrip only once when I couldn't get anything else, because it is so incredible expensive - I can't see why as the finish is not obviously superior, at least when amateur applied by brush.

I found Tillergirl's comments interesting because my experience with International 'Perfection' is quite different. It is a very thin paint, specially the top-coat, and requires no extra thinning except as one gets towards the end of a batch. It is extremely liable to runs and screens. Having someone follow the main painter catching these with a brush is absolutely essential. The timing is crucial as too early and it may run again, too late and the brush will leave marks. But the paint will 'self-heal' minor brush marks as it goes off.

Several undercoats will be desirable if you are making a major colour change, because it goes on thin, but you shouldn't need more than one top-coat.

I can only imagine that Tillergirl was using the paint during a hot spell. At around 15C it takes 8 hours to get touch dry, and for that reason I'd recommend trying to get each coat on before lunch time. If evening dewpoint is reached before it is touch dry, it will ruin the gloss. A full cure takes about a week, so best not to use the boat for a little while after the final coat.


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[MainlySteam]

>>>Why do Awlgrip say that you shouldn't polish or buff the finished paint?<<<

No one has given a reply, so I will just state what I have been told. What I was told is that the linear polyurethanes cure with a hard "skin" on them and so polishing, especially cutting will degrade that and result in regular polishing then being required.

I have no idea how technically correct that is. However, it is my experience that the paint will dry to a high quality gloss finish (unless incorrectly applied, say in cool conditions in which case it will dry dull) which should not require polishing, apart from cleaning, for some years apart from where there has been abrasive damage (eg from fenders) or cutting in a repair.

What we were advised to use for cutting in repairs or for polishing abraded areas is a water soluble compound such as Farecla #6 (which is more abrasive that one would use on softer materials such as gel coat) followed by a wipe on surface glaze (like the 3M one). We do use the compound and have found that alone works well, with no evidence of it being unduly aggressive and it does leave a lasting gloss finish without the need for use of a polish or glaze.

John

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[Two_Hapence]

Hi,

I painted my boat during the spring and I, like Tillergirl, found I needed to thin the International paint I was using. I started at 10% for the undercoats and finished up at 25% for the topcoats.

Without the thinner I had to flatten the paint back and I probably left two thirds of the undercoats as a fine dust in the boatyard before I learned to really thin the paint.

Using a brush to lay off the paint was critical otherwise I got too many bubbles. It was also important to shade the area I was working on for two reasons - to slow down the cure and allow the paint to flow a bit better - to allow us to see where the new paint had gone on.

Regards



Ian

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