Re: Need Advice on issues with duratec high gloss
ALL products need to be measured correctly, the glug glug method doesn't cut it with any of them. When spraying products in a thin film this is even more important, there isn?t enough mass to generate the heat and energy needed for it to cure correctly if the catalyst % and temperature aren?t right.
Duratec can do a few things for you, but there are down sides too. The Duratec (one of their products) manager and I were doing instructional demonstrations at an industry event in Canada and we discussed the product. They think mixing it at different ratios for different layers is a good method, but there can be many problems with that method. They also say to use it at very high ratios, like the 1:1 you mentioned, but they never talk about the down side of that either. Duratec will let the gel coat spray and level better, but this doesn?t mean it makes the product better, it only makes some aspects of it easier to use.
Gel coat uses the pigments in it for almost all of its UV resistance, adding anything to it like a clear resin reduces pigment loading which results in lower UV resistance. If we could lower the pigment content in gel coat by 5% (even 2%) and get the same weathering results we would do it immediately, pigments are expensive and we don?t want to add them if we don?t need to, but we can see differences in testing with only a few % difference in the amount added. So think of what it does when you add their recommended 50% (1:1) to gel coat. One other thing adding Duratec (or anything like it) will do is to change the color, pigment loading can determine color, so reducing it can change the look or color of the product. This is where using different ratios can get you in trouble.
I went to inspect the respray of a 32? sailboat, the person doing the job said the different layers he sprayed were different colors, so when he sanded on the hull and went through one layer and exposed the next it looked different. After discussing it with him I found out he just kind of eyeballed the mixing and changed it a few times to adjust the spray characteristics, then on the final layer he added far more so the surface would be smoother and easier to sand. When he buffed the hull you could see slight differences in color, but the longer it sat outside the more noticeable it became, until it looked terrible.
The person doing the job said the owner wouldn?t accept it and wanted to know what went wrong. The owner happened to pick a color that was very sensitive to pigment loading and changing the mix ratio changed the look of the color, it also changed how it aged in the sun, so in a short period of time it looked bad. The other issue is water resistance, Duratec is not recommended for use under water.
Duratec can make the part ?look? better though, not only does it spray and level better, but when buffing you will typically get a higher gloss, pigments don?t shine well, so the less there is in the mix, the better the surface may look. The slight translucency of the surface compared to gel coat alone can also help, it can look almost like a clear was sprayed over it, it may look much deeper and richer. This can also be a problem though, because being slightly translucent can allow the color of the substrate to show through, and if the final layer isn?t uniform in thickness it may influence final color and possibly look blotchy.
