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Epoxy won't cure


Al Stead
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Hello All,

I'm in the middle of glassing the hull on my weekender.  During the layup I must have mixed a batch of epoxy incorrectly because it only partially cured.  I tore off the glass that didn't give me any fight, and washed down the area with vinegar and then acetone.  It turned out to be most of one side of the hull.  At this point I don't feel any stickiness in the area that I worked over, but I am suspicious of trying to re-glass.  I also noticed that the epoxy was quite a bit more flexible once it set up on my squeege when cleaning it up today.  I typically don't clean up until the epoxy has cured because it is easier to crack it off the plastic once it has hardened. 

What's going on?  Most of the glass is fairly good, but it doesn't make dust like when I used it for glue.  I made up a bit of goop with fairing dust to smooth out some of the areas where the glass ended and the wood begins where I had to tear it off, as a test to see if the epoxy has gone bad or something.  I should say that I am using Marinepoxy.  I have used about a quart for laminating with no problems. I am using  the same bottle for glassing. 

Any thoughts will be gratefully accepted. 

Al

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I have seen epoxy that's gone bad, but the moment you look at it coming out of the container, you know it's questionable. In the same vain, I've used epoxy that was many years past it's shelf life and it still cured hard.

This said, I think you know (unfortunately) what has happened, a grossly incorrect resin/hardener ratio. Okay, we've all gone through this, it happens.

Acetone dilutes the chemicals and if enough is used it'll dilute it to the point that it seems like it all gone. Vinegar stops the chemical reaction, but is less effective at clean up. When looking at a problem like this there really should only be one approach, over kill. The alternative is saving some bucks on clean up, but having a poor bond when you put the 'glass back down.

My idea of over kill is grinding down to what you know is good and starting the process over. This can be a heart breaker if you've just finished a lot of fairing. My first reaction would be just like yours, rip off the 'glass (expletives deleted) then repeatedly scrubbing the area with solvents, until I'm overly convinced it's clean, then use the fine sand paper test. Using the same grit paper you last used before you started applying the 'glass, make several strokes and inspect the grit closely. You're looking for a fouled grit. We all know what it feels and looks like if we sand green epoxy or paint that's not quite dry. If you see this on your paper, then you can try more solvent scrubbing or just kiss off a box of paper and start grinding down to good stuff.

Don't feel bad, we've all done it. You might get lucky and lots of elbow grease, a few scrub brushes (acetone likes to eat these), a 1/4 of a box of gloves, a 1/2 gallon of solvent and a good bit of cussing might yield a clean enough surface for you to lightly scuff (sand) and re-'glass.

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Like Par says;;;

INcorrect mix.

I did that once and had to strip an entire hull bottom of a Spindrift.

No fun!

I used to pump several; pumps of resin followed by several; pumps of hardner making sure the count was correct.  I figured I was smart enough to count well.

After stripping uncured from boat bottom I figure giving up pride is easier than scrubbing bad epoxy mix.

I now never pump a second pump of resin untill I have pumped a pump of hardner.  Always one followed by the other.  Never multiples of one.  OK,  I am not smart enough to count well.

And I also figure it takes far less time to stir a batch of epoxy two minutes staring at a clock than it does to remove a bad batch.

Never had problems since following those two rules.

The opnly other rule I follow is when I start seeing epoxy crystal;s forming in the resin I fill a 5 gallon bucket with full hot water from the hot water tank and set the jug in it untill the crystals are gone and the pump is no longer sticky acting.

And as soon as I feel the pumps suck air I refill the bottles....

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Thanks guys,

It sure took the wind out of my sails.  I really know what that moaning chair is for.  First thing tomorrow, off the the lumber yard to pick up more sanding belts than I can afford.  I use them instead of regular sandpaper because they don't clog quite so quick and I can use a steel brush to clean them at least for a little while. 

I'm pretty sure I know where I went wrong.  I got up before dawn to start mixing goo in the cool hours of the morning so I would have more time to get used to doing big areas.  Unfortunately I should have had that second cup.  I lost count somewhere and didn't have the focus to toss that batch.  I will next time.  It is interesting.  The second side that I did came out pretty good.  Oh well that is a big part of why I am having so much fun on this project.  I like figuring things out.  It might take me longer than I can afford, but it is still fun.

Al

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I never trusted the pumps that much.  I had graduated containers that had pretty accurate markings on them.  I poured or pumped the right amount of resin, then the right amount of hardener, then stirred.  Fill with resin to the 4 ounce line, and then add hardener to the 6 ounce line, and mix.

I did have a couple of mishaps, including a batch that went off very quickly when I poured microballons over the top and it trapped the heat. 

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For the home builder that may build one or two boats, I think the pumps are fine. I've had difficulty with them in the past and don't trust them, but more importantly They take too long to use for many projects. Unlike Ray, I usually can keep track of the number of pump strokes. On the occasions I've lost track, I reverted to the scales. No more, I've been using graduated mixing cups for years and wouldn't go back for nothing. It's much faster to pour to the line (twice) then pump 15 strokes (or what ever) of each into the pot.

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I also use graduated mixing cups.  This time I was using old prescription pill bottles with masking tape on the sides marked with a felt tip pen in 1/2 inch gradations.  Where I messed up was losing count when I was using full bottles two to one.  Not only did I lose count, but I also mixed up which was for what.  Now I have two bottles with nice little solid plugs in the bottom: useless.  Next time, more coffee.

Al

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It took me about three weeks to toss out the pumps.  Usless and can't mix very small batches.  Weight or graduated cups are the only way to go.  My goo fav goo is a 2:1 mix so pouring both parts and looking at what I have insures I get the two parts correct.  I buy in gallon cans or plastic bottles and transfer into cleaned softner bottles.  Blue cap for resin and red cap for hardner.  Just make sure the Mate knows what those bottles are!!!

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I learned something this morning.  I found that if I use pretty coarse paper on my RO sander but only take a couple passes, then use a cut glass scraper to haul off some of the wet wood, the paper lasts a lot longer.  I have been using cut glass scrapers that I get from my local hardware store to smooth out joints during the layup.  They take the epoxy down quickly without creating any dust.  I took down about 2 sq ft to fresh wood in about the last hour, and only went through three sheets of paper.

Thanks for the advice and encouragement.

Al

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Today I glassed over my mistake.  The goo set just fine and it seems that it has stuck to the wood just fine.

  I subsequently learned another lesson.  Get up before dawn if I'm going to do any more mudding.  I tried to fair over some other not so good spots, but at 78 degrees the goo went off on me before I got very far and now I have to take that down.  I'm starting to get pissed now.  I was going to stop when I had a nice solid and waterproof skin on her, but now I'm going for way too nice.  I might as well gain some new skills seeing as how my early June launch goal is out the window. 

She who must be obeyed is getting impatient for me to go back to work for her, so I better quit messing up and start messingabout.

Al

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I'm using Marinepoxy with the medium hardener.  That's not the problem.  I'm just pokey.  I live in Duluth Mn.  right at the tip of Lake Superior.  It is usually cold enough up here to hold off curing for a good while.  Yesterday was near 80, so I got caught working like it was 45. 

This morning I've been feathering the edges of the patch and smoothing out the original layup with both sandpaper and glass scrapers.  It is going pretty well.  I have a question though.  I bought some micro balloon thickener and the container says to cover up any mud with that stuff in it with another layer of epoxy.  Is this really necessary?  I am also mixing some wood flour into it and it sands okay, but not easy.  I would like to smooth out everything one time and go straight to paint. 

Al

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