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| slow epoxy cure http://luthiersforum.com/forum/viewtopic.php?f=10101&t=35503 |
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| Author: | Beth Mayer [ Thu Feb 23, 2012 7:40 pm ] |
| Post subject: | slow epoxy cure |
Hi All, I am pore-filling a EIR OM with Z-Poxy. I used a graduated cup to be as close to 50:50 on resin and hardener as possible. Following Todd Stock's brilliant pore filling vid, (which I have done successfully twice before), I applied the first coat.....1.5 hours ago....it is still tacky. Is it time to panic yet? Will it cure? The z=Poxy was purchased and opened for first use about a year ago. I was careful to clean the tips and cover them well. What do I do if it never cures? 
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| Author: | John Coloccia [ Thu Feb 23, 2012 7:45 pm ] |
| Post subject: | Re: slow epoxy cure |
I've personally never had epoxy actually go bad. Last time I used ZPoxy finishing resin I seem to recall it taking several hours to start getting hard. Longer if it's chilly. |
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| Author: | dberkowitz [ Thu Feb 23, 2012 7:49 pm ] |
| Post subject: | Re: slow epoxy cure |
Beth, give it time. A thin coat takes a while to cure. As for mixing, get yourself a triple beam balance and weigh out the resin and hardener, its much more accurate and you can easily mix up really small batches. |
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| Author: | CharlieT [ Thu Feb 23, 2012 10:44 pm ] |
| Post subject: | Re: slow epoxy cure |
Still tacky at 1.5 hours is normal, so don't sweat it. It'll be tack-free by tomorrow. |
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| Author: | Daniel Minard [ Fri Feb 24, 2012 12:23 am ] |
| Post subject: | Re: slow epoxy cure |
I'm not sure that weighing 1-1 with Z-poxy is gonna give you the right mix. I weighed my Zpoxy containers when I first got them & they were quite a bit different. I guess I could have worked out the appropriate ratio, but it's easy enough to measure, so I didn't bother. As the others already said, leave it overnight. It'll probably be just fine. |
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| Author: | Stuart Gort [ Fri Feb 24, 2012 2:12 am ] |
| Post subject: | Re: slow epoxy cure |
The warmer it is, the sooner is will cure. Bring it in the house overnight if the shop hasn't any heat. In a thin film it takes much longer to set than it does as a mass in a cup...due to exotherm. If the middle of the leftover stuff in the cup is still tacky after several hours...it may have been measured incorrectly. At any rate....if the stuff in the cup EVER gets hard on the surface.....the stuff on the guitar will also cure....eventually. I use a sensitive accurate gram scale to mix epoxy...one that measures in 1/10 gram increments. Two part epoxy really doesn't go bad although it could get cold and the part A could crystallize. You'd be able to see that as a white cloudy material...either settling on the bottom or suspended on the liquid. If you see that....stick it the microwave for a few secs and stir it. |
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| Author: | Stuart Gort [ Fri Feb 24, 2012 2:41 am ] |
| Post subject: | Re: slow epoxy cure |
Daniel Minard wrote: I'm not sure that weighing 1-1 with Z-poxy is gonna give you the right mix. Techincally, the density of parts A & B are different but not enough to change the ratio enough to affect the cure. Z-poxy is designed to be mixed by eye and is therefore, QUITE a bit more forgiving on ratio errors than typical epoxy systems...like West Systems, for instance. Nevertheless....weighing the components provides a standardized way of doing it. If it cures once mixing by weight....that ratio will always cure. I typically mix tiny batches....5g pt. A...5g pt. B. It cures 100% mixing equal amounts by weight.....you must stir it well though. Sometimes I'll add a tiny squit of denatured alcohol before stirring....that helps to facilitate a thorough mixing and it eliminates bubbles for making small castings. |
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| Author: | Kim [ Fri Feb 24, 2012 8:04 am ] |
| Post subject: | Re: slow epoxy cure |
A couple of disposable syringes work perfectly with 50/50 by volume epoxy. You can rinse clean with metho if you have a need to re use them, but at about 20c each......One thing that is a good idea though is to rinse them with metho from new before you draw up any epoxy. Cheers Kim |
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| Author: | Beth Mayer [ Fri Feb 24, 2012 9:42 am ] |
| Post subject: | Re: slow epoxy cure |
Thanks all! Yup, it cured just fine. Sorry about the pre-panic inquiry. One of the reasons I use Z Poxy is because it IS more forgiving in mixing. The last 2 I used it on, I did the coats and left them overnight. This one, I went to check on too soon! Appreciate the hand holding. Beth |
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| Author: | Link Van Cleave [ Fri Feb 24, 2012 10:38 am ] |
| Post subject: | Re: slow epoxy cure |
Also when mixing use a flat bottomed mixing stick so you can scrape the sides and bottom of the cup. Also scrape the sides of the stick and mix some more. Another words mix very thoroughly. L. |
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| Author: | dberkowitz [ Fri Feb 24, 2012 10:51 am ] |
| Post subject: | Re: slow epoxy cure |
When mixing by weight you need to know the ratio by weight not volume. With West, you can use the pumps (highly unreliable in my experience and often makes more than I need) or the cans list the mixing ratios by weight and by hardener type. |
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