IS CA HYDROPHILIC?

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Does anybody here know if CA absorbs water (even a little)? Recently I've been allowing CA to "cure" several days before I sand and polish. While the fnal product is (IMHO) leaps and bounds better than before, I get some small imperfections that develop after a couple days (which doesn't happen with acrylics or Tru-stone).

I'm in the process of doing a test (2 pens from the same blank - one wet sanded and one dry., but I'm wondering if there are any of you who "know for sure" (read chemistry experts)

Thanks in advance,
 
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I sand the bare wood to 220 - maybe 400, finishing up with the grain. And I always clean the surface before I move on to the next grit (I'm kind of a stickler about avoiding cross-contamination).

Not trying to resolve the issue (or be a snobbish ass), just wondering if the CA has a tendency to absorb water.
 
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ChrisN

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What imperfections are you getting? I wet sand my CA immediately after applying 6-8 coats. I then apply a few more and then wet sand down to match the hardware. I haven't noticed anything out of the ordinary yet.

Edit: I just remembered seeing this thread on another forum: http://woodbarter.com/showthread.php?tid=7786 I didn't try using water as an activator myself, but I just thought I'd leave this here FWIW.
 
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Exabian

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I sand the bare wood to 220 - maybe 400, finishing up with the grain. And I always clean the surface before I move on to the next grit (I'm kind of a stickler about avoiding cross-contamination).

Not trying to resolve the issue (or be a snobbish ass), just wondering if the CA has a tendency to absorb water.

The reason for my question was find out if you use a cut-n-polish wax like EEE before applying your CA (i guess I could just asked that). But you don't so I'm out.
 
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ChrisN - The imperfections are surface irregularities (ripples?). I sand and polish and I'm very pleased with the finish (like I said, I'm fussy). So I think I'm done and I assemble. But after a couple more days, the "ripples" appear. They're not horrible, it's just that the finish was glass smooth and now it isn't. Only happens with the CA.

Lucky2 - I normally clean the blank with acetone.

Jaywood1207 - Yes. Actually some time after the blank is dry. Like I said, I'm allowing the CA to cure for a couple days after application. Then I sand (wet - to 2000) and polish (Novus 3 & 2) then a quick buff on the Beall wheels. Looks great but the imperfections appear some time (1 or 2 days) later.
 

its_virgil

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Acetone is the solvent for CA. Don't know if it matters but cleaning with a known CA solvent seems suspect. Water will easily dissolve into alcohol so using denatured alcohol may not be the best. I use CA accelerator in the bottle for cleaning. It dries very fast and has not proven to be detrimental to my CA finish. Its rather strange that the ripples develop after a few days from a smooth and glassy surface on a CA finish. Puzzeling?\
do a good turn daily!
Don
 
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Don - Puzzling? You bet!

I use an accelerator but thought it might be part of the issue so I've suspended using it for a while.

Yes, I'm aware that acetone is a CA solvent . But it's so volatile, I figured it would be gone before I applied. HOWEVER - that may be my next "trial case". Thanks for the input.

Note - I've sent an email to the CA supplier noted above. Will share reply.
 
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ChrisN

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Mercury's site (linked earlier in the thread) has something interesting to say about accelerator.

The Mercury MH16 Accelerator is a solvent that is used to speed up the cure of CA. It typically is one of three base ingredients, Alcohol, Heptane, or Acetone. Alcohol is the least aggressive and most substrate friendly product. Heptane is a very good all purpose accelerator as far as speed and substrate compatibility goes. Acetone is the most aggressive and least substrate compatible product. Most available accelerators are either Acetone or Heptane.

I thought Acetone was a CA solvent, not an accelerator!:confused::confused: I also checked the MSDS sheet for Mohawk Instant glues at work (that's what we use), and they say that water causes polymerization (curing). If you have a CA glue spill big enough to cause problems:rolleyes:, you are to flood it with water to make it cure. I think it's highly unlikely that using water too soon would cause ripples a few days later. It more likely would get mixed into the CA and cause it to become cloudy. Maybe your wood is moving?:confused:
 

1080Wayne

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Ted , the problem you are having is almost certainly related to the thickness of your finish . You speak of how much your finishes improved when you started to let them cure for a couple days before sanding . A couple days is adequate for a fairly thin (1-2 thou ???) finish , but a week is much better if you are really laying it on to fill in pores or surface imperfections . I would suggest rough sanding after a couple days to even out the coating thickness . This will allow it to cure more uniformly over the next couple days . Use the nose test . If you can smell CA after sanding , it is NOT fully cured .

The alternative to the above is to just put on a thinner coat of CA .
 

Wildman

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I say yes, because all surfaces have trace amounts of moisture on them. This trace amount of moisture should actually help CA cure. They change the formula for medical CA, as body heals CA no longer a factor.

At 0 to 70% RH should not affect curing. At 70% and higher with high temperature may affect CA. Also age of the CA you are using can cause problems too!

Don’t forget wood is hydroscopic, and never as dry as we think!
 
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Got a response from Satellite City Instant Glues. They said (in part) "CA glue is very reactive to water when it is uncured. It will cure extremely rapidly, bubble, and turn white. However, after it is cured, it is waterproof. We recommend allowing 24 hours to elapse between the initial cure and any contact with water, because cyanoacrylate takes 24 hours to achieve its full cure. I can't think of a reason that wet sanding after a couple of days would have the effect you describe." Thanks to them for the quick reply.
 

Rick_G

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I've had ripples develop in wood pens months after, turned out to be wood movement. The wood was not dry enough when I made the pen and as the wood dried some areas shrunk while others stayed the same depending on grain direction. After about a year I took the pen apart sanded it smooth and refinished no problems since. I now microwave dry all the blanks I cut myself and have had no problems since.

ChrisN - The imperfections are surface irregularities (ripples?). I sand and polish and I'm very pleased with the finish (like I said, I'm fussy). So I think I'm done and I assemble. But after a couple more days, the "ripples" appear. They're not horrible, it's just that the finish was glass smooth and now it isn't. Only happens with the CA.
.
 

kooster

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For whatever my TCW . . . CA application and moisture are not best buds. Any application during high humidity days should be avoided. Not sure if this applies but again, it's only MTCW.
 

Wood Butcher

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I was doing a Rockler demo some time back and forgot to take my accelerator (aerosol can) and didn't want to break a new can for a single pen or two. I remembered that heat and moisture can speed the CA cure sooooo; I got real close and breathed on the still uncured CA. It worked; the CA cured quickly; it also fogged up so bad you couldn't see the wood grain. Had to tool it off and start over with more patience.
WB
 

Dragonlord85

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Ted, one thing not mentioned is how are you sealing the ends of the blanks? If the ends of the blanks are not sealed prior to wet sanding then you could be reintroducing moisture to the wood causing it to move.
 
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