Epoxy won't set up.

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weller
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Epoxy won't set up.

Post by weller » Sun Oct 28, 2012 1:41 pm

I'm using poxy shield. I put three coats of epoxy on when I fiberglassed the hull. I left it sit for a week then sanded, and sanded, and sanded. I went back over the low spots with thickened expoy. Now some of the spots will not set up. When I sand it gums up the paper.So I got all the bad epoxy off and tried to fill the lows spots again, now they won't set up. I tried this 3 times with the same result. The mix ratio is right and like I said only some spots won't set up and others are fine. Any suggestions?
"My mind is on a permanent vacation, the ocean is my only medication"

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Roberta
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Re: Epoxy won't set up.

Post by Roberta » Sun Oct 28, 2012 2:41 pm

Some epoxies take several days to several weeks befoe they are hard enough to sand without gumming up the paper. You may also have amine blush, which is a by product of the curing process. It looks a lot like uncured epoxy and is sticky to the touch. This needs to be cleaned off before applying more epoxy and before sanding. Temperature will also affect the cure time of epoxy. Colder temps will take longer for full curing.

Roberta
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weller
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Re: Epoxy won't set up.

Post by weller » Sun Oct 28, 2012 5:52 pm

Thanks I will clean the sticky spots and see what happens.
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Bill Edmundson
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Re: Epoxy won't set up.

Post by Bill Edmundson » Mon Oct 29, 2012 5:50 am

My help didn't always do a thorough job mixing the epoxy and hardner. While sanding yesterday I hit a spot that must have gotten very little hardner. Paint scraper to the job! Nothing like patching a new boat.

Bill
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Roberta
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Re: Epoxy won't set up.

Post by Roberta » Mon Oct 29, 2012 6:11 am

Nothing like a good paint scraper. I have several in different sizes.

Roberta :D
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Bill CNC
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Re: Epoxy won't set up.

Post by Bill CNC » Mon Oct 29, 2012 10:33 am

Thoroughly mix the epoxy well, before adding in anything else to the mix. Sometimes people add everything together then mix, ... only to find disaster peeking from around the corner.

Fillers will absorb what ever they come in contact with. Be it poorly mixed epoxy "OR" thoroughly mixed epoxy. If it absorbed the poorly mixed or not mixed epoxy it will create soft spots such as your describing.
Bill

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weller
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Re: Epoxy won't set up.

Post by weller » Mon Oct 29, 2012 1:16 pm

I mix the epoxy for at least a minute and a half before adding any filler then another minute after I add the filler.
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falconer100
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Re: Epoxy won't set up.

Post by falconer100 » Tue Oct 30, 2012 3:57 pm

Make sure your scraping the sides and bottom, especially the corners of the mixing pot, if you don't, you will end up with resin spots with no hardener.
Someone told me you are trying to mix two components that don't really want to mix. Best advice I had on mixing epoxy.

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Bill CNC
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Re: Epoxy won't set up.

Post by Bill CNC » Tue Oct 30, 2012 4:23 pm

The way I make my thickened epoxy is somewhat different than most.

I mix the 2 parts for at least 3 minutes, depending on the ambient temperature. If I cannot get what I need done in the time allotted for that particular hardener, I switch to a slower hardener.

Another thing I do, ... is I mix in the filler(s) and mix another 3-5 minutes longer. This is really pushing the time for the hardener, so I spread it thin on a paper plate, then insert the paper plate into a large zip lock bag and put the whole shebang into the freezer for about 5 minutes.

This is to ensure that the filler(s) absorb the epoxy and I dont have dry spots and to slow down the cure rate.

It may seem like an off the path way of doing it, ... but it works like a champ. I can also extend the cure time of the epoxy when it feels like it's getting warm by sticking it back into the freezer for a few minutes. This method only works when you spread your mix thin on a paper plate. In a cup, ... the center will start to harden making the batch useless.

This is ALL DONE AFTER the parts have been primed with epoxy first.

Try a small batch like that and try it out for yourself.
Bill

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dherrema
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Re: Epoxy won't set up.

Post by dherrema » Wed Oct 31, 2012 9:22 am

A quick way to tell if it's soft epoxy or amine blush is to use a hair dryer and give it a blast of warm air for a bit and then give it the smell test: A stinky waxie smell is amine blush, chrispy sharp epoxy smell is a bad cure. "Don't burn your nose" or touch it when hot!!
I know it's a little subjective, but don't get it too hot and melt the underlying epoxy.

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weller
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Re: Epoxy won't set up.

Post by weller » Wed Oct 31, 2012 1:41 pm

Well I cleaned the whole side of the boat and now it sands fine. Thanks for the tip Roberta I was hoping you where right. I used 13 gallons of epoxy up to this point and if I mixed them wrong I would be in BIG trouble. Thanks everyone for the tips, this is what makes this sight priceless.
"My mind is on a permanent vacation, the ocean is my only medication"

Paul Kinneberg
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Re: Epoxy won't set up.

Post by Paul Kinneberg » Wed Oct 31, 2012 4:21 pm

weller wrote:Well I cleaned the whole side of the boat and now it sands fine. Thanks for the tip Roberta I was hoping you where right. I used 13 gallons of epoxy up to this point and if I mixed them wrong I would be in BIG trouble. Thanks everyone for the tips, this is what makes this sight priceless.
13 gallons :o Really? What boat are you building?

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weller
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Re: Epoxy won't set up.

Post by weller » Wed Oct 31, 2012 6:23 pm

Atlantic skiff
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pauloman
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Re: Epoxy won't set up.

Post by pauloman » Mon Apr 01, 2013 11:25 am

experienced epoxy folks get sloppy and sometimes don't get the mix ratio right or sloppy mixing. I had one 'customer' tell me that I didn't tell him he had to mix the epoxy vertically in the bucket as well as just spinning his mixing stick in one place.

It is common for pouring epoxy table tops or beginners to epoxy floors to have end up with sticky spots. This is the result of trying to use every last drop of epoxy in the bucket. No matter how well you mix the epoxy on the sides and corners where the bottom and sides meet are never well mixed. Epoxy is NOT good to the last drop.

If you worry about this the best fix is to mix in one bucket then pour the mix into a second bucket and mix some more. The 'bad' stuff from the first bucket is the last thing to go into the second bucket - so it ends up in the top middle of the second bucket and gets well mixed when the second bucket is mixed again.

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Re: Epoxy won't set up.

Post by khundley » Mon Apr 01, 2013 2:56 pm

When using the System III epoxies as grain fillers on my guitars, they have always recommended mixing in one container, then when everything has been added (if you are using solids of some sort) mix it again in another container to prevent catching any unmixed material from the sides of the first container. Always thought it good advice, and always got burned by it when I didn't. And I was only mixing a tablespoon of it at a time....I can imagine the risks in the amounts used on a boat.
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