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Thinning out epoxy--what to use?
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Author:  John Elshaw [ Mon Feb 20, 2006 5:14 am ]
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What do you guys use to thin out epoxy? Does thinning epoxy effect it's strength at all other than there is less of it if it goes on thinner? I assume that once the thinning agent evaporates, the remaining epoxy will be the same as any other mixed at regular viscosity, correct?

Thanks!

John
Author:  Pwoolson [ Mon Feb 20, 2006 5:27 am ]
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Denatured Alcohol thins it. I'm not sure about the structural effects but my guess is that it might weaken it a bit.
Author:  j.Brown [ Mon Feb 20, 2006 5:56 am ]
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John, thats how I understand it. The higher the DA content, the less Epoxy is left behind. I don't think it has an effect chemically on the integrity of what is left behind.
-j.
Author:  Steve Kinnaird [ Mon Feb 20, 2006 6:08 am ]
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Guys, as I understand it, strength is not an issue, IF you are using that epoxy to fill pores.

Ain't that so?

SK
Author:  Alan Carruth [ Mon Feb 20, 2006 6:28 am ]
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I've used about 25% alcohol by volume to thin out 5-minute epoxy to use as a filler. Thin the resin and hardener seperately, then mix them. The setting time is longer; about 15 minutes, and the epoxy stays a bit 'rubbery' for a day or more. It also, of course, shrinks.
Author:  j.Brown [ Mon Feb 20, 2006 7:45 am ]
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If used as a filler, then there is no issue. Thats correct. I thinned down my final 2 or 3 coats of epoxy to 50% and wiped them on with a sock. It worked perfectly.
-j.
Author:  LarryH [ Mon Feb 20, 2006 7:52 am ]
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Here's a different approach that I discovered while trying to speed the cure time. Apply heat from a hair dryer and it flows like water and shouldn't effect its strength.

I would imagine getting it too hot is going to effect it in a negative way but it flows really well this way, soaks in deeply as a pore filler and can be scraped virtually clean for easier sanding.

Larry
Author:  Brook Moore [ Mon Feb 20, 2006 8:01 am ]
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Epoxy can be thinned with at least 3 solvents: acetone, lacquer thinner, and
denatured alcohol. I would guess that MEK might work also. All of them
have a weakening effect, with acetone the least and alcohol the most. To
quote a WEST system document: "Adding 5% lacquer thinner to epoxy
reduces the epoxy’s compressive strength by 35%".

This same document goes on to say that thinned epoxy should not be used
as a structural adhesive. Thinning also can cause extended cure time,
increased shrinkage, and increased flexibility.

Since filling wood pores is not structural, thinning is probably OK, but I
would not recommend it for the first coat.
Author:  ATaylor [ Mon Feb 20, 2006 8:34 am ]
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So, sorry for this sillyquestion (kidding!). And I also don't want to hijack this thread but... You guys use epoxy for pore filling instead of the specific pore filling product like ColorTone grain filler? Does it work equally as well? I hated the ColorTone filler - it just didn't seem to work as advertised.
Anyway - thinned epoxy sounds like a great way to go. It also sounds like heated epoxy would be naturally thinned, flow well and not lose any strength like thinning does. I need to check this out!
Author:  Frank Ford [ Mon Feb 20, 2006 9:17 am ]
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Far as I know, it goes something like this:

Add thinner to epoxy, and the epoxy cures by chemical reaction but stays
in solution until solvent evaporates, which, depending on thickness of
film, can be a right smart while. As the solvent slowly escapes, the film
shrinks just as other coatings do, the amount depending on how much
the epoxy was diluted.


Personally, I'd avoid using thinner, but go for lower viscosity epoxies that
are formulated to flow as coatings. West System has a slow version of its
hardener that works that way, and System Three has a nice clear bar top
coating that's pretty runny.



Author:  KiwiCraig [ Mon Feb 20, 2006 10:36 am ]
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Thanks for that Mr. Ford.

Is the slower west system the 206 hardner ?

Is this what you use as pore filler?

How long does it take to set up?

I am concerned on it impregnating the wood to deeply because of it's slow set up . Should I be ?

Don't like the idea of my beautiful Mahogany becoming an Ovation type back !

Thanks in advance, KiwiCraig
Author:  John Elshaw [ Mon Feb 20, 2006 11:08 am ]
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Thanks for all the info guys. This will be very helpful next time I need to pore-fill a guitar. For now, I need to go thin some epoxy and fix a major Pinewood Derby mistake. Hmm, maybe I should have my son put a nice rosewood binding/purfling scheme on his car!   

John
Author:  Frank Ford [ Mon Feb 20, 2006 11:23 am ]
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206 is is the slow hardener, and I think the 207 is the thin viscosity stuff.
I've not used that particular product but I've heard good things about it.

by the way, I hope I didn't give the wrong impression. I've thinned epoxy for
a variety of non-instrument applications, but I have not tried it for pore
filler. I'm still using the traditional silex and linseed based paste wood filler,
usually the dark walnut color. I'm refiishing the back of a D-28 this week,
and I'll use that stuff on it, after painting on a bit of lacquer over the center
strip, of course.
Author:  A Peebels [ Mon Feb 20, 2006 1:02 pm ]
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I used West system epoxy back when I made radio controlled airplane fuselages in a female mold with fiberglass ,carbon fiber,kevlar etc. I remember thinning with denatured alcohol and the fuselages coming out like rubber. A second layer unthinned would support the outer layer untill it eventually hardened. I agree with Larry H. the heat gun will not only reduce the viscosity, but will reduce the curing time both of which are good things.


Al
Author:  LarryH [ Mon Feb 20, 2006 1:26 pm ]
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[QUOTE=A Peebels]I agree with Larry H. the heat gun will not only reduce the viscosity, but will reduce the curing time both of which are good things.[/QUOTE]

Al, I said hairdryer, not heat gun. I wouldn't try a heat gun myself except VERY carefully - too hot I'm thinkin'.

Larry
Author:  arvey [ Mon Feb 20, 2006 1:27 pm ]
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I mix up the West system and give it about 5 min. and then add laquor thinner. Otherwise I find the cure time to be too slow. I use the 205 thinner
Author:  A Peebels [ Mon Feb 20, 2006 2:09 pm ]
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Larry: Yup heat gun works great you just back off a little and be careful.

Al
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