CA adhesion?

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Gabericks

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Oct 12, 2019
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South Carolina
Good morning pros,
I've been turning for about a year and a half now and all of a sudden I'm seeing a problem. I put about 10 layers of medium CA on a pen, with a quick spray of activator in between. I let it dry overnight before wet sanding and micro meshing.
My problem is I'm noticing 1 or 2 small white spots at the end of the barrel where the CA looks like maybe the first layers didn't adhere well to the wood? At first I thought it was sand through but I found that there's a pocket under the CA that I can stick my pocket knife blade under and flick off, exposing the bare wood. Any suggestions?
 
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robutacion

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Aug 6, 2009
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Australia - SA Adelaide Hills
Sounds like the wood was contaminate with something oily, most folks will wipe the blank with acetone before starting the CA application, apart from that, CA separation can also happen when removing the barrels from the bushes if CA got in there.
You don't say if this happens before the pen assembly or after, as assembling can do that if barrels too tight sometimes from dry CA inside the tubes.

How hold is your CA...?

Cheers
George
 

leehljp

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Oily residue, mostly with oily blanks such as different ebony woods and a few others - will decrease the adhesion. That PLUS the way the CA'ed blanks are separated from bushings. It is common/normal to build up layers of CA on the bushings as it builds up on the blank. The separation of the bushings from the blanks, whether by scoring the CA at the joint line between the blank and bushing, or especially if they are just broken off - this action creates enough pressure to fracture the adhesion just enough to cause "lift" of the CA off of the blank.

Careful scoring the CA to the bushings at the joint line helps, but another way is through TBC, or Turning Between Centers without bushings during the finishing process. Bushings can be used to get the blank to size and shape, but are removed for the finishing. This eliminates the fracture pressure/shock that causes lift.

TBC was a tip that I picked up from a couple of other guys on this forum when I had the same problem about 13 years ago. It eliminates the use of the mandrel and simplifies the whole process of finishing. I haven't used a mandrel for pens since. Many others haven't either. Give TBC a try.
 
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leehljp

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And another note:


In this search above, you will see that your question and problem is quite common. And you will see that I have replied to most of them, because I too had that problem once, and then found the best solution on oily wood was to not finish with the bushings on. Of course CA will get onto the centers, but the height distance between the blank's end and the "centers" allows for the break to be along the lines of the tubing more than on the wood surface.
 

Pierre---

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Jun 10, 2012
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France
If it was because of oily wood, it would not occur only at the ends. Maybe you sanded, cut or trimmed the ends a bit aggressively, or just remove the bushings that were stuck after the CA application with too much energy. Usually, you can add a dash of thin CA under the white spot. If it doesn't work, do it again !
Conical nylon bushings for finishing are your friends.
 

leehljp

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If it was because of oily wood, it would not occur only at the ends. Maybe you sanded, cut or trimmed the ends a bit aggressively, or just remove the bushings that were stuck after the CA application with too much energy. Usually, you can add a dash of thin CA under the white spot. If it doesn't work, do it again !
Conical nylon bushings for finishing are your friends.
Pierre,
or just remove the bushings that were stuck after the CA application with too much energy.
This is the problem 99% of the time. To those just getting started or those who are just starting to use oily wood such as ebonies, most are unfamiliar with what you (or I) would suggest as too much energy. The degree of force or energy is highly subjective from one person to another. But it is this "snapping" of the bushings off that initiates the gradual loss of adhesion on the ends. Just above you post, I posted a link to a search that can go back 10 years on the subject and the vast majority is "lifting" (or loss of adhesion) on the ends.

And as you said, Nylon bushings (as well as TBC) help greatly in decreasing the problem.
 

PreacherJon

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Aug 28, 2019
Messages
151
Location
Ohio
Good morning pros,
I've been turning for about a year and a half now and all of a sudden I'm seeing a problem. I put about 10 layers of medium CA on a pen, with a quick spray of activator in between. I let it dry overnight before wet sanding and micro meshing.
My problem is I'm noticing 1 or 2 small white spots at the end of the barrel where the CA looks like maybe the first layers didn't adhere well to the wood? At first I thought it was sand through but I found that there's a pocket under the CA that I can stick my pocket knife blade under and flick off, exposing the bare wood. Any suggestions?
I'm not sure about the white spots... other than you had some kind of contaminate on the end... could be the wood itself. But I have to say from my experience, that to many coats. For wood, I sand down to about 380 grit and I don't wipe off the dust that is left after that last sanding. It will help fill in any spots when applying the first CA layer. I put a very light thin coat on and like you... use accelerant. Then I do a second coat of thin coat.. and accelerant. Then use the same process with two coats of medium. I then directly use my micro mesh... no need to weight over night with this process.
 
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