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Removing Epoxy


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#11 Frank

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Posted 08 October 2019 - 03:21 PM

As a thought, if I were to bush hardener over the unset stuff, would it harden?

Or even harden enough to sand/mechanically remove?

Although if it didn't harden in correct ratios, it probably never will.

Wheels, I wasn't mixing products, this was a fresh layer

Brushing the hardener probably wont help, it is not like the catalyst for polyester, try a strong solvent like acetone or paint thinners and scrub with a coarse steelo pad like the SS ones. I have also had luck with painting a coat of interprotect over the gummy surface and then scraping or sanding that off after it set  good luck !


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#12 BOIGuy

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Posted 08 October 2019 - 05:05 PM

Too much hardener tends to stop epoxy setting, you must measure very carefully. A little bit extra just to be sure is enough to cock it up.


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#13 wheels

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Posted 08 October 2019 - 05:30 PM

Once again, Epoxy thinners. Nothing else. Epoxy thinners is the only thinner that will remove the stuff. WEAR GLOVES.
Sorry, no you can't bush over the hardener. It doesn't work that way unfortunately.

Sorry, I had thought you had gone and bought just an Ados hardener.
As BOIguy said, you need the exact ratio of resin and hardener to get the best result. The difference with Epoxies is that the hardener is like a bunch of keys that exactly fit a bunch of locks, being the Resin. An incorrect mix leaves a bunch of either locks of keys unmatched and stuck in the hardened mix. If the mix is too far out or wack, you end up with a tacky mess.
Low ratio mixes like 2:1 ratios tend to be much more forgiving. High mix ratios like 5:1 require exacting measurements. In fact, high ratio mixes are best weighed rather than measured due to temperature differences causing volume changes. Although small differences won't be noticed, the strength of the cured mix is. That may not be critical for most of us, but mission critical situations requiring best possible strength requires perfect mixes and post curing with heat to ensure all keys are in al the locks so to speak.


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#14 madyottie

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Posted 08 October 2019 - 06:49 PM

Ok, so I popped in to our local fibreglass expert after work today.

According to him...

Acetone won't work.
M.E.K may work.

Having tried tonight, M.E.K helped to soften it slightly, but wouldn't actually remove it.

Scraper and 40grit sandpaper kinda works.

Surprisingly, Vinegar actually seemed to work quite well, except that I used the same rag I'd used for the mek, so now I need to buy more vinegar for the kitchen cupboard.

All is not lost, it seems.

Fortunately this is the prototype blade. I have another foam blank in the shed, waiting patiently for my glassing skills to improve.

Ideally I'd like to include carbon in the final product, so it could be a long wait.

Thanks all for the replies. I'll buy a big pack of Steelo pads tomorrow, and keep on scrubbing
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3mm ply is no match for 110kg size 11 boots! Anyone know how to fix my foredeck?

 


#15 Dtwo

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Posted 08 October 2019 - 09:07 PM

Meths.  Sounds just wrong but I have been using it for years to clean epoxy brushes, thin epoxy for sealing and wiping up.  If I was in your scenario (nothing to lose) I would:

- orientate the rudder so leading edge up

- 2 or 3 layers of paper towels over the bits you want to clean

- saturate with meths

- cover with cling film so meths stays in and air out

- leave overnight

- have at least one beer while repeating to yourself "I will never mix products again"

- see what it looks like in the morning

 

All is not lost yet!


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#16 Steve Pope

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Posted 10 October 2019 - 12:57 PM

I usually use meths to dilute epoxy to get a better penetration / sealing on the first coat.


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#17 wheels

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Posted 10 October 2019 - 06:12 PM

Yes Meths will thin epoxy. But you do need to be aware that Meths absorbs moisture from the air and so putting it into Epoxy also puts moisture into the Epoxy. There are also a couple of other products in Meths that are not solvents and thus also contaminate Epoxy. As a cleaner, it is fine. Overseas, Methanol is often used as a poison in Meths. But in NZ, Methanol is no longer used. However, I am not sure about Oz, where Super cheap and Bunnings products come from.

Cellulose thinners will also thin Epoxy. But it isn't cheap stuff. The bigger problem is that it is has a very fast evaporation rate and you will likely lose 50% of it to the air before it dissolves the Epoxy.

Epoxy thinners is a mix of three different solvents. It does not evaporate as fast as the thinner above. Nor do they absorb moisture. It easily evaporates out of an epoxy mix leaving nothing behind.

The advantages of either the above thinners is that it will break down Epoxy that maybe tacky, but not fully cured. Which in this case, sounds to be the issue. So it should be the best to use in my view.
Meths does not act as a solvent to nearly cured Epoxy. So it may not work as well at removing the tacky stuff.

Acetic Acid (Vinegar) stops the cross linking process and thus stops the curing process dead in its tracks. However, it will not actually mix with epoxy. It will help in breaking down the sticky stuff on your hands. BUT DO NOT use it to thin epoxy.


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#18 mcp

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Posted 10 October 2019 - 06:22 PM

Yes Meths will thin epoxy. But you do need to be aware that Meths absorbs moisture from the air and so putting it into Epoxy also puts moisture into the Epoxy. There are also a couple of other products in Meths that are not solvents and thus also contaminate Epoxy. As a cleaner, it is fine. Overseas, Methanol is often used as a poison in Meths. But in NZ, Methanol is no longer used. However, I am not sure about Oz, where Super cheap and Bunnings products come from.

Cellulose thinners will also thin Epoxy. But it isn't cheap stuff. The bigger problem is that it is has a very fast evaporation rate and you will likely lose 50% of it to the air before it dissolves the Epoxy.

Epoxy thinners is a mix of three different solvents. It does not evaporate as fast as the thinner above. Nor do they absorb moisture. It easily evaporates out of an epoxy mix leaving nothing behind.

The advantages of either the above thinners is that it will break down Epoxy that maybe tacky, but not fully cured. Which in this case, sounds to be the issue. So it should be the best to use in my view.
Meths does not act as a solvent to nearly cured Epoxy. So it may not work as well at removing the tacky stuff.

Acetic Acid (Vinegar) stops the cross linking process and thus stops the curing process dead in its tracks. However, it will not actually mix with epoxy. It will help in breaking down the sticky stuff on your hands. BUT DO NOT use it to thin epoxy.

 

What are they using in place of Methanol in NZ now?   Surely its not pure ethanol?

 

Back on the main subject.  You didn't mentioned Acetone in the above?   I have used this for clean up and it does a great job.  Is there a reason you have left this out or is one of the ingredients in the epoxy thinners?  or? 


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#19 wheels

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Posted 11 October 2019 - 04:21 AM

Is there a reason you have left this out

 

Yes there is  reason I left it out. It's called getting old and forgetfulness
Acetone is good. I use it a lot for all sorts of things because it is the one solvent that is not actually toxic to us. Although that does not mean it is non toxic. We still need to take care using it. Acetone is naturally occurs in our bodies in the event of Insulin/diabetes issues, so our bodies have learned to deal with small amounts of it. Where as many other solvents are extremely harmful to us. Including Ethanol.
 

Not sure what NZ made Meths has added. I believe they now use an additive that makes one vomit. Methanol, being poisonous, still never stopped someone desperate enough from drinking the stuff. So I guess they figured it was better to try and stop someone taking it in another way. Which makes sense to me.


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#20 madyottie

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Posted 13 October 2019 - 08:34 PM

In the end I tried most things (excluding actual Epoxy Thinners) but the only thing that really worked was a scraper and 40grit sandpaper.

At this point I've got as far as a first undercoat.

Still a bit more sanding to do between coats to get the best finish, but all-up weight at this point is a little over a kilo.

Ended up being a few mm too narrow as it is, but easy to fix that problem.
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3mm ply is no match for 110kg size 11 boots! Anyone know how to fix my foredeck?

 





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