Official Luthiers Forum!

Over the past several months there have been a few post where some have said that they followed the cure time on the label of various brands of epoxy before sanding, but still had gum up issues. A prime example is Zpoxy the label claims a 3hr cure time. This is a bonding and handling cure time not full hardness cure. On Zpoxy, this cure time is is for application of a fiberglass over coating, Zpoxy's intended use. When we use epoxy as a pore filler we need for it to cure as hard as possible so that we can easily sand it back with out gumming up. So keep in mind when reading instructions and cure schedules on labels that they refer to the intended use of the product. and may not reflect the cure time required to effectively sand.

Excellent point, Michael. I recently sanded back Zpoxy that was applied months ago...there was a noticable difference in how it sanded compared to over night cure out. I don't know what the magic time is but I plan to wait at least 2 days before sanding.

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JJ
Napa, CA
http://www.DonohueGuitars.com

*groan* More waiting...sometimes I wish for a magic finish that you could just dip a guitar into and voila, all shiny and perfect. Oh, well, one can dream right?

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Joe Breault
Merrimack, NH
Perpetual novice

Good things come to those who wait.

MichaelP, I had some gumming after an overnight cure time, should we wait the 2 days JJDonohue recommends or longer? ZPoxy I am referring to.

Mike
White Oak, Texas

Then you did not get the mix right or you were in cool climitic conditions. If the mix is close to 50% hardner and 50% epoxy then it should haden to sandable in 12-24 hrs. Now it is also possible that you got a bad batch. It happens with every brand now and then.

Mike,
I've had issues too when the zpoxy did not cure in 24 hours. But it was related to the mixture being correct. I always just pour a quarter size dollop on parchment paper of each of the resin and hardner, then I add just a touch more hardener to make sure it will harden correctly(mix up with a toothpick after this). In other words, I'd rather have too much hardener than not enough. Good luck Mike!
Tracy

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Tracy
http://www.luthiersuppliers.com

Fortunately it was my pore fill coat and I sanded it back down to the wood leaving on the pore fill. Just one little spot. I follow with the 2 coats of very thin ragged on coats to finish leveling and pop the grain as (the MichaelP method)

Thanks for the info. Probably just did not get enough hardner. It was not a major problem and everything has worked out, but thanks for the input.

I run my shop at around 78 degrees (AC/Heat) and RH is 45% using a dehumidifier.

Mike
White Oak, Texas

[QUOTE=JBreault] *groan* More waiting...sometimes I wish for a
magic finish that you could just dip a guitar into and voila, all shiny
and perfect. Oh, well, one can dream right?[/QUOTE]

How about a 50 gallon drum of Super Glue!!??!!

Louis

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- Louis Freilicher

Oh No! Not another learning experience!

groan* More waiting...sometimes I wish for a magic finish

MEKP cured polyester....

Yup, catalized poly is the quickest thing out there... Too bad about the extreme toxicity, flammability and the need for a high tech booth...

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

Sad, so sad.....

It can also be brushed(yes, brushed) succesfully. Booth? what booth...?

Another thought to keep in mind is that it's not good to breath epoxy
fumes. I usually forget, but most packages will warn you. I think it may
be a sensitizer too. Wear those respirators!

Mike

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Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

Curing temperature makes a big difference. If you can get the temp up to about 100F curing time will be significantly reduced.

Al

[QUOTE=Mario] Sad, so sad.....

It can also be brushed(yes, brushed) succesfully. Booth? what booth...?[/QUOTE]

Brushes? We can use stinking brushes? How very interesting... Would the results be as good as sprayed? (Of course I guess it depends largely on the brushee!).

I seem to recall you saying that you needed a profesional set-up to use this very nasty stuff. Isn't is supposed to kill you in 10 seconds flat? Just kidding...

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I'd like to be able to prove, just for once, that money wouldn't make me happy...