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| Doughy Epoxy http://www.hobie.com/au/en/forums/viewtopic.php?f=20&t=6931 |
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| Author: | Doc Thirst [ Mon Jun 04, 2007 4:40 pm ] |
| Post subject: | Doughy Epoxy |
Not even sure if that is a good way to describe this problem. I put on 4 or so coats of West epoxy so far, each time I allowed for a day or so dry time before I sanded. I got up to sand my 5th coat yesterday and it took me a couple of sheets of 100 grit to get though it. It normally only takes 2 or 3 pieces. The paper had epoxy stuck to it like gum after only a minute or so of sanding, but I managed to get it sanded, and it had a nice texture after I was done. Another issue was the lack of dust, most of the epoxy ended up on the paper, but I could see it balling up. It acted like it was still wet, but it had well over a day of dry time. Could it perhaps be the humidity, because the 6th coat is acting the same way. Should I pull it out in the sun to see if I can get a harder cure? |
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| Author: | srm [ Tue Jun 05, 2007 9:16 am ] |
| Post subject: | |
I'm not sure whether humidity effects the curing of epoxy. I've heard both that it does and doesn't. However, temperature will definitely effect cure time. Also, if you didn't measure each part to the correct proportions or if you didn't mix sufficienty, the batch may not cure. I've also been told that if epoxy has been allowed to sit in a cold environment for long enough, it will crystalize, which will effect it's ability to cure. If the epoxy crystalizes, the solution is to place it in hot water for a period of time. sm |
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| Author: | Hobie Nick [ Tue Jun 05, 2007 9:43 am ] |
| Post subject: | |
Definitely check your mixing ratios. If they are off by too much you will not get a proper cure. Also, humidity does effect some epoxies. Call West System, or check out their website, for more details. If you want to raise the temp, I would not put it out in the sun as the UV will cause the epoxy to blush making your painting prep work that much harder. |
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| Author: | Doc Thirst [ Tue Jun 05, 2007 10:10 am ] |
| Post subject: | |
Thanks for the replies fellas. I let it rest last night and we are having an nice 88 temp day here today. I left the garage door open this morning so hopefully it will be an ideal day to dry...assuming that does the trick. Either way I'll sand tonight and see what Im left with. Worse case I'll use a ton of sand paper and have to put on a 7th coat to even it out. If this does happen I'll prob hold off doing so until tomorrow to allow for some post sanding dry time. I'm pretty bummed as I was moving right along with things and was hoping to be painting tonight. My mixing isn't precise, but its close, I tend to be heavier on the hardener. I'm leaning towards a humidity issue as that is the only change I can think of between coats 4 and 5. It has rain daily here for the last few days. I'll let you know how it turns out. |
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| Author: | DVL [ Tue Jun 05, 2007 5:05 pm ] |
| Post subject: | |
From: Gougeon Brothers on Boat Construction Book, Chapter 11 page 81. Humidity affects the cure and you shouldn't epoxy above 85% humidity at 70 degrees F. Great book if your interest is wood & epoxy. I have other books on boat repair (fiberglass) as well. |
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| Author: | Doc Thirst [ Wed Jun 06, 2007 5:45 am ] |
| Post subject: | |
Thanks man that makes me feel a little better. I opted to take it all the way down to one of the earlier (harder) coats. It took me about 3 hours of sanding, and 12 sheets, but I got there. Once at that point I hit it with some 220 and it really sanded out nice. I totally planned on sliding back into my epoxy routine, but it looked so nice I just said the hell with it. Around 10 pm I slapped on my first coat of primer and it looks amazing. If the primer looks this good, I can't wait to see how the paint is going to finish. |
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